(90 days)
The Focus Technologies West Nile Virus IgM Capture ELISA is intended for qualitatively detecting IgM antibodies to West Nile virus in human serum. In conjunction with the Focus Technologies West Nile Virus ELISA IgG, the test is indicated for testing persons having symptoms of meningioencephalitis, as an aid in the presumptive laboratory diagnosis of West Nile virus infection. Positive results must be tested using the background subtraction method (either on the initial test or on a repeat test). Positive results must be confirmed by neutralization test, or by using the current CDC guidelines for diagnosing West Nile encephalitis. This test is not intended for self-testing, and this test is not FDA cleared nor approved for testing blood or plasma donors. Assay performance characteristics have not been established for automated instruments.
Indirect Enzyme-linked immunosorbent assay for qualitatively detecting human serum IgM antibodies to West Nile virus.
Here's a summary of the acceptance criteria and the studies that demonstrate the device meets those criteria, based on the provided text:
Acceptance Criteria and Device Performance
The provided document does not explicitly state "acceptance criteria" in a separate, clear table with pre-defined thresholds. However, the performance characteristics studies implicitly define the expected performance benchmarks based on agreement with reference assays and clinical classifications. For the purpose of this response, I will synthesize the performance results as the "reported device performance" and infer "acceptance criteria" from the documented agreements and sensitivities/specificities deemed acceptable for regulatory submission.
Note on Background Subtract: The device's performance is consistently evaluated both "without Background Subtract" and "with Background Subtract." The Intended Use explicitly states that "Positive results must be tested using the background subtraction method," suggesting that the performance with background subtract is the clinically relevant and accepted performance. Therefore, the table below will primarily focus on the "with Background Subtract" results as the crucial performance metrics, but acknowledge the "without" where significant differences exist.
| Acceptance Criterion (Inferred from Study Results and Predicate Device Performance) | Reported Device Performance (with Background Subtract) |
|---|---|
| Clinical Sensitivity (Encephalitis/Meningitis Patients: Confirmed WNV) | 93.2% (41/44) (95% CI 78.3-97.5%) |
| Agreement with Presumptive CDC IgM ELISA (Presumed Positive WNV) | 100% (2/2) (95% CI 15.8-100%) |
| Agreement with Presumptive CDC IgM ELISA (Presumed Negative WNV) | 100% (250/250) (95% CI 98.6-100%) |
| Serological Sensitivity (WNV PRNT Positive) | 100% (70/70) (95% CI 94.9-100%) |
| Negative Agreement with Presumptive WNV IFA (WNV IFA Negative) | 98.1% (101/103) (95% CI 93.2-99.8%) |
| Serological Sensitivity (Suspected Encephalitis/Meningitis, Confirmed WNV) | 100% (1/1) (95% CI NA) |
| Negative Agreement with Presumptive CDC IgM ELISA (Suspected Encephalitis/Meningitis, Presumptive Negative) | 100% (49/49) (95% CI 92.7-100%) |
| Positive Agreement with Presumptive CDC IgM ELISA (Non-Flavivirus Test Samples, CDC Positive) | 66.7% (2/3) (95% CI 9.4-99.2%). (Note: This rate is for non-flavivirus test samples, not primary WNV suspected cases; the sample size is very small. Without background subtract, it was 33.3%). |
| Negative Agreement with Presumptive CDC IgM ELISA (Non-Flavivirus Test Samples, CDC Negative) | 100% (469/469) (95% CI 99.2-100%) |
| Cross-Reactivity with other Flaviviruses/Pathogens | Varies significantly by pathogen. For example, Dengue virus (secondary infections) showed 40.0% positivity with background subtract. St. Louis Encephalitis not tested with background subtract, but was 53.8% positive without. Other pathogens showed 0% positivity with background subtract (e.g., Herpes simplex, Epstein-Barr, Cytomegalovirus, Borrelia burgdorferi, Rheumatoid factor, Anti-nuclear antibodies, Polio virus). |
| Reproducibility (Inter-Lab, Inter-assay, Intra-assay) | Coefficients of Variation (CVs) were generally low for positive samples and higher for negative/equivocal samples (e.g., for BS22 (positive), Inter-Lab %CV 2.1, Inter-assay %CV 7.6, Intra-assay %CV 3.4 with background subtract). |
| Specificity (2-mercaptoethanol treatment) | 100% (15/15) of WNV IgM/IgG positive samples became IgM negative after 2-ME treatment, indicating IgM specificity. |
| Freeze-Thaw Stability | No changes in interpretation were observed for positive or negative samples across up to 5 freeze-thaw cycles. |
Study Details:
-
Sample size used for the test set and the data provenance (e.g. country of origin of the data, retrospective or prospective)
- Study Site 1 (Encephalitis/Meningitis Patients):
- Sample Size: 300 patients. 44 confirmed positive (WNV encephalitis/meningitis symptoms, CDC IgM ELISA positive and WNV PRNT positive), 256 presumptive results (250 presumed negative, 2 presumed positive, 4 excluded).
- Data Provenance: Sera were sequentially submitted to a state department of health laboratory located in the northeastern U.S., archived, and masked. Prospective collection from clinical suspicion.
- Study Site 2 & 4 (WNV PRNT Positives):
- Sample Size: 75 retrospective samples (70 ultimately tested with background subtract).
- Data Provenance: Retrospective samples from a clinical laboratory (mid-western U.S.) with no clinical information, pre-screened positive by Focus and confirmed by WNV PRNT.
- Study Site 3 (West Nile IFA Negatives):
- Sample Size: 103 samples.
- Data Provenance: Reactive samples that were West Nile IFA negative, from a clinical laboratory located in the southwestern U.S. (Retrospective implied by "assessed reactive samples").
- Study Site 4 (Suspected Encephalitis/Meningitis Patients):
- Sample Size: 50 samples.
- Data Provenance: Archived and masked sera from a U.S. federal government laboratory. One confirmed positive by WNV PRNT, 49 presumptively negative by CDC ELISA for arboviruses.
- Study Site 4 (Non-Flavivirus Test Samples):
- Sample Size: 476 samples (4 samples were indeterminant with CDC IgM ELISA and excluded from final calculations).
- Data Provenance: Prospectively collected from North America during August 2003. Submitted to a clinical laboratory in Southern California for non-flavivirus tests.
- Cross-Reactivity Study (Study Site 1 & 4):
- Sample Size: 75 samples sero-positive to other potentially cross-reactive pathogens.
- Data Provenance: Retrospective and masked sera. DOH (northeastern U.S.) tested St. Louis encephalitis positives, Focus (Study Site 4) tested others.
- Specificity (2-ME treatment, Study Site 4):
- Sample Size: 15 sera.
- Data Provenance: Sera positive for both WNV IgM and IgG.
- Freeze-Thaw Study (Study Site 4):
- Sample Size: 8 sera (5 positive, 3 negative).
- Data Provenance: N/A (likely in-house selection).
- Reproducibility Studies (Inter-lot, Inter/Intra-assay, Inter-laboratory):
- Sample Size: Varies by study: 5 samples for inter-lot, 7 for inter/intra-assay (63 data points), 7 for inter-laboratory. Masked duplicates were used.
- Data Provenance: Study Site 4 (Focus), Study Site 5 (mid-western U.S. clinical lab), Study Site 6 (northern California university lab), Study Site 1 (northeastern U.S. state DOH lab), Study Site 2 (mid-western U.S. clinical lab assumed different from site 5 for variety).
- Study Site 1 (Encephalitis/Meningitis Patients):
-
Number of experts used to establish the ground truth for the test set and the qualifications of those experts (e.g. radiologist with 10 years of experience)
The document does not specify the "number of experts" or their "qualifications" involved in establishing the ground truth. Ground truth was primarily established using reference assays such as:- CDC West Nile Virus IgM ELISAs
- West Nile Virus Plaque Reduction Neutralization Test (WNV PRNT)
- West Nile IFA
- Clinical criteria for encephalitis/meningitis (fever, altered mental status, CSF pleocytosis, etc.)
These reference methods are established laboratory techniques, implying their performance is well-understood and accepted, but the exact human expert involvement in interpreting these for ground truth is not detailed.
-
Adjudication method (e.g. 2+1, 3+1, none) for the test set
The document does not describe an explicit adjudication method (like 2+1 or 3+1 consensus). Ground truth was determined by comparing the device's results to a predefined reference standard (e.g., CDC IgM ELISA, WNV PRNT, WNV IFA, or clinical criteria), which implicitly serves as the adjudication or definitive determination. -
If a multi reader multi case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance
This is an in vitro diagnostic (IVD) device, specifically an ELISA assay. The concept of "human readers" for an "AI" assistance is not applicable in the context of this type of diagnostic test. The results of an ELISA are typically read by a spectrophotometer and interpreted based on a cutoff value, rather than a human "reader" making subjective interpretations that could be "assisted" by AI. Therefore, an MRMC comparative effectiveness study involving human readers with/without AI assistance was not done. -
If a standalone (i.e. algorithm only without human-in-the-loop performance) was done
Yes, the studies presented are standalone performance evaluations of the Focus Technologies West Nile Virus IgM Capture ELISA. The device (an immunoassay kit) itself is the "algorithm" in this context, providing a quantitative output that is then interpreted against a cutoff. The performance metrics (sensitivity, specificity, agreement) directly reflect the device's ability to classify samples independently of human interpretational variability beyond reading the spectrophotometer. The "background subtract procedure" is an integral part of the assay's interpretive algorithm to mitigate false positives, as described in the "Test Principle" section. -
The type of ground truth used (expert consensus, pathology, outcomes data, etc.)
The ground truth was established using reference laboratory assays (CDC WNV IgM ELISA, WNV PRNT, WNV IFA) and clinical diagnostic criteria for encephalitis/meningitis (which implicitly involves expert clinical judgment and outcomes). In some cases, previous positive screening results by other methods were also used to enrich the sample set. There is no mention of pathology (histopathological examination) or long-term outcomes data being used directly as ground truth for all studies, although the "confirmed" positive cases were patients with symptoms of meningioencephalitis. -
The sample size for the training set
The document does not specify a separate "training set" for the device. As an ELISA kit, it is a chemical/biological assay rather than a machine learning algorithm that requires explicit training data in the same sense. The performance characteristics were evaluated on various test sets as described above, but these are typically considered validation sets for an established assay methodology, rather than a "training set" that a machine learning model would use to learn parameters. -
How the ground truth for the training set was established
Since no explicit "training set" is mentioned in the context of a machine learning algorithm, this question is not directly applicable. If one considers the development and optimization of the ELISA assay itself, the ground truth would have been established during the research and development phase through various experiments using known positive and negative samples, similar to the reference assays used in the validation studies (e.g., using WNV PRNT confirmed samples, CDC ELISAs). However, the document does not detail this R&D process.
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JUN 3 0 2004
14085
510(k) Summary of Safety and Effectiveness West Nile Virus IgM Capture ELISA Catalog No. EL0300M Prepared June 28, 2004 Page 1 of 8
| Applicant | Focus Technologies, Inc.10703 Progress WayCypress, California 90630USA |
|---|---|
| Establishment RegistrationNo. | 2023365 |
| Contact Person | Michael J. Wagner, Esq.tel (714) 220-1900fax (714) 995-6921mwagner@focustechnologies.com |
| Summary Date | June 28, 2004 |
| Proprietary Name | West Nile Virus IgM Capture ELISA |
| Generic Name | West Nile Virus IgM Capture ELISA |
| Classification | West Nile Virus Serological Reagents21 CFR §866.3940Class II |
| Predicate Device | Focus Technologies Arbovirus IFA IgM (K913618)Focus Technologies HSV-2 ELISA (K993724)Focus West Nile Virus IgM Capture ELISA (K031952)CDC West Nile Virus IgM Capture ELISAWest Nile Virus Plaque Reduction Neutralization Test |
Device Description
Indirect Enzyme-linked immunosorbent assay for qualitatively detecting human serum IgM antibodies to West Nile virus.
Intended Use
The Focus Technologies West Nile Virus IgM Capture ELISA is intended for qualitatively detecting IgM antibodies to West Nile virus in human serum. In conjunction with the Focus Technologies West Nile Virus ELISA IgG, the test is indicated for testing persons having symptoms of meningioencephalitis, as an aid in the presumptive laboratory diagnosis of West Nile virus infection. Positive results must be tested using the background subtraction method (either on the initial test or on a repeat test). Positive results must be confirmed by neutralization test, or by using the current CDC guidelines for diagnosing West Nile encephalitis. This test is not intended for self-testing, and this test is not FDA cleared nor approved for testing blood or plasma donors. Assay performance characteristics have not been established for automated instruments.
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Test Principle
In the Focus Technologies West Nile Virus IgM Capture ELISA, the polystyrene microwells are coated with anti-human antibody specific for IgM (u-chain). Diluted specimen samples and controls are incubated in the wells, and IgM present in the sample binds to the anti-human antibody (IgM specific reactants are removed by washing. Recombinant WNV antigen is then added to the wells and incubated, and, if anti-WNV IgM is present in the sample, the WNV antigen binds to the anti-WNV in the well.
Unbound WNV antigen is then removed by washing the well Mouse anti-flavivirus comjugated with horseradish peroxidase (HRPO) is then added to the wells and, if WNV antigen has been retained in the well by the anti-flavivirus in the sample, the mouse anti-flavivirus: HRPO binds to the WNV antigen in the wells. Excess conjugate is removed by washing. Enzyme substrate and chromogen are added, and the color is allowed to develop. After adding the Stop Reagent, the resultant color change is read by a spectrophotometer. The color intensity is compared to the Cut-off's to determine if antigen-specific IgM is present in the sample.
Background Subtract Procedure
All IgM reactive samples must be tested with the background subtract procedure to check for false positives caused by cross-reacting antibodies (e.g., RF and heterophilic antibodies) and other substances. Heterophile antibodies are antibodies that can be present in the patient specimen and can bind to animal antibodies (for example the Capture Wells contain rabbit antibody and the Anti-flavivirus Contains mouse antibody). The background subtract procedure detects false positives by testing initially positive samples with and without West Nile Antigen and comparing the reactivity. If heterophile antibodies are present in the sample, they will cross-link the Capture Well antiflavivirus Conjugate, and both wells will be reactive. If heterophile antibodies are absent, then only the well with Antigen will be reactive. The background subtraction method will not eliminate false positive results due to cross-reactive antibodies to other flaviviruses (e.g. St. Louis encephalitis, dengue etc).
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K040854 510(k) Summary of Safety and Effectiveness West Nile Virus IgM Capture ELISA Catalog No. EL0300M Prepared June 28, 2004 Page 3 of 8
Expected Values
The prevalence of West Nile antibodies varies depending age, geographic location, testing method used, and other factors. A community based serosurvey for West Nile infection conducted in New York in 2000 found that 0.2% (5/2433) of persons tested overall had antibodies indicating recent West Nile infection, and that 1.1% (2/176) of persons reporting a recent headache and fever had antibodies indicating a recent. West Nile infection. Two serosurveys conducted in New York City (NYC) in 1999 and 2000 showed that approximately 1 in 150 infections (<1%) resulted in meningitis or encephalitis. The NYC results are consistent with a 1996 Romanian serosurvey indicating that 1:140 to 1:320 infections resulted in meningitis or encephalitis.
Prevalence in Samples Submitted for Non-Flavivirus Testing (n=476)
Focus assessed reactivity with 476 samples prospectively collected from North America during August 2003. The samples had been submitted to a clinical laboratory located in Southern California for non-flavivirus tests (e.g., tests for other infectious diseases). The samples consisted of 64.1% females, and 1.5% from persons of unspecified gender.
Study Site 4: Focus Reactivity with Non-Flavivirus Test Samples (n = 476)
Focus assessed the device's reactivity with 476 samples prospectively collected from North America during August 2003. The samples had been submitted to a clinical laboratory located in Southern California for infectious diseases. Positive samples were tested with a CDC WNV IgM ELISA and/or the CDC WNV IgG ELISA.
IgM Results without Background Subtract Prevalence with Samples Submitted for Non-Flavivirus Testing (n=476)
IgM results with Background Subtract Prevalence with Samples Submitted for Non-Flavivirus Testing (n=476)
| Age | Neg | Eqv | Pos | % Positive | 95%CI |
|---|---|---|---|---|---|
| 0 to 9 | 24 | 0 | 0 | 0.0% (0/24) | 0.0-14.2% |
| 10 to 19 | 28 | 0 | 1 | 3.5% (1/29) | 0.1-17.8% |
| 20 to 29 | 70 | 0 | 0 | 0.0% (0/70) | 0.0-5.1% |
| 30 to 39 | 82 | 0 | 0 | 0.0% (0/82) | 0.0-4.4% |
| 40 to 49 | 77 | 0 | 1 | 1.3% (1/78) | 0.0-6.9% |
| 50 to 59 | 48 | 1 | 2 | 3.9% (2/51) | 0.5-13.5% |
| 60 to 69 | 38 | 0 | 1 | 2.6% (1/39) | 0.1-13.5% |
| 70 to 79 | 34 | 0 | 0 | 0.0% (0/34) | 0.0-10.3% |
| 80+ | 17 | 1 | 0 | 0.0% (0/18) | 0.0-18.5% |
| Unknown | 50 | 1 | 0 | 0.0% (0/51) | 0.0-7.0% |
| Overall | 468 | 3 | 5 | 1.1% (5/476) | 0.3-2.4% |
| Age | Neg | Eqv | Pos | % Positive | 95%CI |
|---|---|---|---|---|---|
| 0 to 9 | 24 | 0 | 0 | 0.0% (0/24) | 0.0-14.2% |
| 10 to 19 | 29 | 0 | 0 | 0.0% (0/29) | 0.0-11.9% |
| 20 to 29 | 70 | 0 | 0 | 0.0% (0/70) | 0.0-5.1% |
| 30 to 39 | 82 | 0 | 0 | 0.0% (0/82) | 0.0-4.4% |
| 40 to 49 | 78 | 0 | 0 | 0.0% (0/78) | 0.0-4.6% |
| 50 to 59 | 51 | 0 | 0 | 0.0% (0/51) | 0.0-7.7% |
| 60 to 69 | 38 | 0 | 1 | 2.6% (1/39) | 0.1-13.5% |
| 70 to 79 | 34 | 0 | 0 | 0.0% (0/34) | 0.0-10.3% |
| 80+ | 17 | 0 | 1 | 5.6% (1/18) | 0.1-27.3% |
| Unknown | 51 | 0 | 0 | 0.0% (0/51) | 0.0-7.0% |
| Overall | 474 | 0 | 2 | 0.4% (2/476) | 0.1-1.5% |
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Performance Characteristics
Performance characteristics without background subtract are in the beft column, and with background subtract is in the right column.
Study Site 1: Focus Reactivity with Encephalitis/Meningitis Patients (n = 300)
A state department of health laboratory located in the northeastern U.S. assessed the device's reactivity from encephalitis meningitis patients (n = 300). Patients were suspected of having either viral meningitis. Viral encephalitis criteria included: 1) fever, 2) altered mental status and/or other evidence of cortical involvement; and 3) CSF pleocytosis with predominant lymphocytes and/or elevated protein and a negative gram stain and culture.15 Viral meningitis criteria included: 1) fever, 2) headache, stiff neck and/or other meningeal signs; and 3) CSF pleocytosis with predominant lymphocytes and/or elevated protein and a negative gram stain and culture).12 The sera were sequentially submitted to the laboratory, archived, and masked. The reference methods were the CDC IgM ELISAs, and a plaque reduction neutralization test (PRNT) for West Nile virus. Of 300 encephalitis/meningitis patients, 44 were classified as confirmed positive West Nile encephalitis/neningitis symptoms. CDC IgM ELISA positive and WNV PRNT positive) and 256 had presumptive assay results (CDC WNV IgM ELISA) . 4 of the 256 presumptive assay results showed NS and were excluded.
Without Background Subtract
The Focus IgM assay was positive with 90.9% (40/44) of the confirmed positive WNV encephalitis patients (including 2 Focus equivocals calculated as negatives). Of the 252 patients with presumptive assay results, 250 were classified as presumed negative patients (CDC WNV IgM ELISA negative), and 2 were classified as presumed positive West Nile encephalitis patients (CDC WNV IgM ELISA positive). The Focus IgM assay was positive with 100% (2/2) of the presumed positive WNV encephalitis patients. The Focus IgM assay was negative with 99.6% (249/250) of the presumed negative patients (including 1 Focus equivocal calculated as positive).
| Study Site 1: Focus Reactivity with |
|---|
| Encephalitis/Meningitis Patients (n=300) |
| SpecimensCharacterized byReference Assays | Neg | Eqv | Pos | Total | % |
|---|---|---|---|---|---|
| Clinical sensitivity(encephalitis ormeningitis symptoms,CDC IgM ELISApositive and WNVPRNT positive) | 2 | 2 | 40 | 44 | 90.9% (40/44)95%CI 78.3-97.5% |
| Agreement with thepresumptive CDCIgM ELISA | 249 | 1 | 0 | 250 | Positive100% (2/2)95%CI 15.8-100%Negative99.6% (249/250)95%CI 97.8-100% |
With Background Subtract
The Focus IgM assay was positive with 90.9% (40/44) of the confirmed positive WNV encephalitis patients (including 2 Focus equivocals calculated as negatives). Of the 252 patients with presumptive assay results, 250 were classified as presumed negative patients (CDC WNV IgM ELISA negative), and 2 were classified as presumed positive West Nile encephalitis patients (CDC WNV IgM ELISA positive). The Focus IgM assay was positive with 100% (2/2) of the presumed positive WNV encephalitis patients. The Focus IgM assay was negative with 100% (250/250) of the presumed negative patients.
Study Site 1: Focus Reactivity with Encenhalitis/Meningitis Patients (n=300)
| Encephalitis/Meningitis Patients (n=300) | |||||
|---|---|---|---|---|---|
| SpecimensCharacterized byReference Assays | Neg | Eqv | Pos | Total | % |
| Clinical sensitivity(encephalitis ormeningitis symptoms,CDC IgM ELISApositive and WNVPRNT positive) | 2 | 1 | 41 | 44 | 93.2% (41/44)95%CI 78.3-97.5% |
| Agreement with thepresumptive CDCIgM ELISA | 250 | 0 | 0 | 250 | Positive100% (2/2)95%CI 15.8-100%Negative100% (250/250)95%CI 98.6-100% |
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510(k) Summary of Safety and Effectiveness
West Nile Virus IgM Capture ELISA Catalog No. EL0300M Prepared June 28, 2004
Page 5 of 8
Performance Characteristics (continued)
Study Site 2 & Study Site 4: Focus Reactivity with WNV PRNT Positives (n = 75)
Focus (background subtract) and a clinical laboratory (screening procedure) located in the mid-western U.S. assessed the device's reactivity with 75 retrospective samples with no clinical information that were pre-screened positive (by Focus) with a West Nile virus native antigen ELISA'.0, and confirmed West Nile positive by plaque reduction neutralization test (PRNT). The sera were sequentially submitted to the laboratory, archived, and masked.
Without Background Subtract
The clinical laboratory located in the mid-western U.S. determined that the Focus IgM ELISA was positive with 100% (75/75) of the WNV PRNT positive samples.
Study Site 2: Focus Reactivity with WNV PRNT
Positives (n = 75)
| SpecimensCharacterized byReference Assays | Focus WNV IgM ELISA Results | ||||
|---|---|---|---|---|---|
| Neg | Eqv | Pos | Total | % | |
| Serologicalsensitivity (WNVPRNT positive) | 0 | 0 | 75 | 75 | 100% (75/75)95%CI 95.2-100% |
| Positives (II – 70) | |||||
| SpecimensCharacterized byReference Assays | Neg | Eqv | Pos | Total | % |
| Serologicalsensitivity (WNVPRNT positive) | 0 | 0 | 70 | 70 | 100% (70/70)95%CI 94.9-100% |
With Background Subtract
Focus determined that the Focus IgM ELISA was positive with 100% (70/70) of the WNV PRNT positive samples. Five samples were QNS for the background subtract procedure.
Study Site 2: Focus Reactivity with WNV PRNT Positives (n = 70)
- Five of the 75 samples were QNS.
Study Site 3: Focus Reactivity with West Nile IFA Negatives (n=103)
A clinical laboratory located in the southwestern U.S. assessed reactive samples that were West Nile IFA negative. 13
Without Background Subtract
The Focus IgM ELISA was negative with 96.1% (99/103) of WNV IgM IFA negative samples (including one equivocal calculated as positive).
Study Site 3: Focus Reactivity with West Nile IFA Negatives (n=103)
| SpecimensCharacterized byReference Assays | Focus WNV IgM ELISA Results | ||||
|---|---|---|---|---|---|
| Neg | Eqv | Pos | Total | % | |
| Negative agreementwith presumptiveWNV IFA | 99 | 1 | 3 | 103 | 96.1% (99/103)95%CI 90.3-98.9% |
| SpecimensCharacterized byReference Assays | Focus WNV IgM ELISA Results | ||||
| Neg | Eqv | Pos | Total | % | |
| Negative agreementwith presumptiveWNV IFA | 101 | 1 | 1 | 103 | 98.1% (101/103)95%CI 93.2-99.8% |
With Background Subtract
The Focus IgM ELISA was negative with 98.1% (101/103)) of WNV IgM IFA negative samples (including one equivocal calculated as positive).
Study Site 3: Focus Reactivity with West Nile IFA Negatives (n=103)
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K040854 510(k) Summary of Safety and Effectiveness West Nile Virus IgM Capture ELISA Catalog No. EL0300M Prepared June 28, 2004 Page 6 of 8
Performance Characteristics (continued)
Study Site 4: Focus Reactivity with Suspected Encephalitis/Meningitis Patients (n= 50)
Focus assessed the device's reactivity with 50 samples from patients mening tis. A U.S. federal government laboratory provided the archived and masked sera. One sample was confirmed positive by WNV PRNT, and the other 49 were presumptively negative (CDC ELISA) for arboviruses present in North America (LAC, EEE, SLE and WNV).
Without Background Subtract
The Focus IgM ELISA was negative with 98.0% (48/49) of the WNV presumptive negative samples, and positive with the one WNV PRNT confirmed sample.
Study Site 4: Reactivity Suspected with Encephalitis/Meningitis Patients (n= 50)
| SpecimensCharacterized byReference Assays | Focus WNV IgM ELISA Results | ||||
|---|---|---|---|---|---|
| Neg | Eqv | Pos | Total | % | |
| Serologicalsensitivity (CDCIgM ELISA positiveand WNV PRNTpositive) | 0 | 0 | 1 | 1 | 100% (1/1)95%CI NA |
| Negative agreementwith presumptiveCDC IgM ELISA | 48 | 0 | 1 | 49 | 98.0% (48/49)95%CI 89.1-99.9% |
With Background Subtract
The Focus IgM ELISA was negative with 100% (49/49) of the WNV presumptive negative samples, and positive with the one WNV PRNT confirmed sample.
Study Site 4:Focus Reactivity with Suspected Encephalitis/Meningitis Patients
| SpecimensCharacterized byReference Assays | Focus WNV IgM ELISA Results | % | |||
|---|---|---|---|---|---|
| Neg | Eqv | Pos | Total | ||
| Serologicalsensitivity (CDCIgM ELISA positiveand WNV PRNTpositive) | 0 | 0 | 1 | 1 | 100% (1/1)95%CI NA |
| Negative agreementwith presumptiveCDC IgM ELISA | 49 | 0 | 0 | 49 | 100% (49/49)95%CI 92.7-100% |
Study Site 4: Focus Reactivity with Non-Flavivirus Test Samples (n = 476)
Focus assessed the device's reactivity with 476 samples prospectively collected from North America during August 2003. The samples had been submitted to a clinical laboratory located in Southern California for infectious diseases. Positive samples were tested with a CDC WNV IgM ELISA.
Without Background Subtract
The Focus West Nile IgM Capture ELISA was negative with 99.4% (468/471) of the CDC ELISA IgM negative samples (including 3 Focus equivocals included as positive), and positive with 33.3% (1/3) of the CDC ELISA IgM positive samples.. Four CDC ELISA IgM indeterminant samples were excluded from the calculations.
Study Site 4: Focus Reactivity with Non-Flavivirus Test Samples (n = 476)*
| SpecimensCharacterized byReference Assays | Focus WNV IgM ELISA Results | ||||
|---|---|---|---|---|---|
| Neg | Eqv | Pos | Total | % | |
| Positive agreementwith presumptiveCDC IgM ELISA | 0 | 2 | 1 | 3 | 33.3% (1/3)95%CI 0.8-90.6% |
| Negative agreementwith presumptiveCDC IgM ELISA | 468 | 1 | 0 | 469 | 99.8% (468/469)95% CI 98.8-100% |
- Excludes four samples that were indeterminant with the CDC IgM ELISA.
With Background Subtract
The Focus West Nile IgM Capture ELISA was negative with 100% (469/469) of the CDC ELISA IgM negative samples, and positive with 66.7% (2/3) of the CDC ELISA IgM positive samples.. Four CDC ELISA IgM samples were excluded from indeterminant the calculations.
| Study Site 4: Focus Reactivity with Non-Flavivirus |
|---|
| Test Samples (n = 476)* |
| SpecimensCharacterized byReference Assays | Neg | Eqv | Pos | Total | % |
|---|---|---|---|---|---|
| Positive agreementwith presumptiveCDC IgM ELISA | 1 | 0 | 2 | 3 | 66.7% (2/3)95%CI 9.4-99.2% |
| Negative agreementwith presumptiveCDC IgM ELISA | 469 | 0 | 0 | 469 | 100% (469/469)95% CI 99.2-100% |
- Excludes four samples that were indeterminant with the CDC IgM ELISA.
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Performance Characteristics (continued)
Focus Cross-reactivity
Focus (Study Site 4) and a state department of health laboratory located in the northeastern U.S. (DOH) (Study Site 1) assessed the device's cross-reactivity with sera that were sero-positive to other potentially cross-reactive pathogens (n = 75). The DOH tested the SLE positives, and Focus tested the other sera. The sera were retrospective and masked. The results of the studies are summarized in the table below:
| Focus Cross-reactivity without Background Subtract | ||||||
|---|---|---|---|---|---|---|
| Specimenscharacterized byReference Assays | Site | Focus WNV IgM ELISA Results | % Positive | |||
| Neg | Eqv | Pos | Total | |||
| Dengue virus(secondaryinfections) | 4 | 6 | 1 | 8 | 15 | 40.0% (6/15)95%CI 16.3-67.7% |
| St. Louisencephalitis virus | 1 | 6 | 0 | 7 | 13 | 53.8% (7/13)95%CI 25.1-80.8% |
| Eastern equineencephalitis virus | 4 | 2 | 0 | 0 | 2 | 0.0% (0/2)95%CI 0.0-84.2% |
| Herpes simplexvirus | 4 | 18 | 1 | 1 | 20 | 10.0% (2/20)95%CI: 1.2-31.7% |
| Epstein-Barr virus | 4 | 19 | 0 | 0 | 19 | 0.0% (0/19)95%CI 0.0-17.6% |
| Cytomegalovirus | 4 | 13 | 0 | 1 | 14 | 7.1% (1/14)95%CI 0.2-33.9% |
| Borreliaburgdorferi | 4 | 0 | 0 | 1 | 20 | 5.0% (1/20)95%CI 0.1-24.9% |
| Rheumatoid factor | 4 | 0 | 1 | 4 | 20 | 25.0% (5/20)95%CI 3.7-49.1% |
| Anti-nuclearantibodies | 4 | 0 | 0 | 1 | 20 | 5.0% (1/20)95%CI 0.1-24.9% |
| Polio virus | 4 | 10 | 0 | 0 | 10 | 0.0% (0/10)95%CI 0.0-30.8% |
| Focus Cross-reactivity with Background Subtract | ||||||
|---|---|---|---|---|---|---|
| Specimenscharacterized byReference Assays | Site | Neg | Eqv | Pos | Total | % Positive |
| Dengue virus(secondary infections) | 4 | 9 | 3 | 3 | 15 | 40.0% (6/15)95%CI 16.3-67.7% |
| St. Louisencephalitis virus* | NA | NA | NA | NA | NA | Not tested. |
| Eastern equineencephalitis virus | 4 | 2 | 0 | 0 | 2 | 0.0% (0/2)95%CI 0.0-84.2% |
| Herpes simplexvirus | 4 | 20 | 0 | 0 | 20 | 0.0% (0/20)95%CI: 0.0-16.8% |
| Epstein-Barr virus | 4 | 19 | 0 | 0 | 19 | 0.0% (0/19)95%CI 0.0-17.6% |
| Cytomegalovirus | 4 | 13 | 0 | 1 | 14 | 0.0% (0/14)95%CI 0.0-23.2% |
| Borreliaburgdorferi | 4 | 20 | 0 | 0 | 20 | 0.0% (0/20)95%CI: 0.0-16.8% |
| Rheumatoid factor | 4 | 20 | 0 | 0 | 20 | 0.0% (0/20)95%CI: 0.0-16.8% |
| Anti-nuclearantibodies | 4 | 20 | 0 | 0 | 20 | 0.0% (0/20)95%CI: 0.0-16.8% |
| Polio virus | 4 | 10 | 0 | 0 | 10 | 0.0% (0/10)95%CI 0.0-30.8% |
- Positive and equivocal SLE samples were not tested with the background subtract procedure.
Focus Reproducibility
Focus (Study Site 4), a clinical laboratory located in the mid-west United States (Study Site 5), and a university laboratory located in northern California (Study Site 6) assessed the reproducibility of the assay with and without the background subtract procedure. Each laboratory tested seven samples in three runs per day for three days. Of the seven samples, three samples were negative (BS1, BS2 and BS6), two samples were positive in the assay and with background subtract (BS22 and BS3), and two samples were positive in the assay but negative in background subtract (BS21 and BS23, these samples were masked replicates). The studies are summarized in the tables below:
| Focus Reproducibility without Background Subtract | |||||
|---|---|---|---|---|---|
| --------------------------------------------------- | -- | -- | -- | -- | -- |
| ID | MeanIndex | Inter-Lab%CV | Inter-assay%CV | Intra-assay%CV |
|---|---|---|---|---|
| BS1 | 0.06 | 36.9 | 42.5 | 15.4 |
| BS6 | 0.07 | 22.5 | 31.2 | 13.2 |
| BS2 | 0.09 | 15.1 | 27.6 | 14.7 |
| BS22 | 1.49 | 1.5 | 5.2 | 3.0 |
| BS3 | 2.49 | 3.6 | 6.2 | 3.7 |
| BS21* | 2.72 | 24.4 | 23.3 | 4.3 |
| BS23* | 2.75 | 25.3 | 24.0 | 2.6 |
- These samples were masked replicates
Focus Reproducibility with Background Subtract
| ID | MeanIndex | Inter-Lab%CV | Inter-assay%CV | Intra-assay%CV |
|---|---|---|---|---|
| BS1 | NA | NA | NA | NA |
| BS6 | NA | NA | NA | NA |
| BS2 | NA | NA | NA | NA |
| BS22 | 1.46 | 2.1 | 7.6 | 3.4 |
| BS3 | 2.47 | 1.2 | 8.6 | 3.6 |
| BS21* | -0.08 | -92.0 | -198.3 | -351.7 |
| BS23* | -0.06 | -41.8 | -194.2 | -127.6 |
- These samples were masked replicates
{7}------------------------------------------------
Performance Characteristics (continued)
Specificity of the Focus WNV IgM Assay
Focus (Study Site 4) assessed specificity of the WNV IgM Assay by selecting fifteen different sera that were positive for both WNV IgM and IgG. The sera were treated with 5 uL of 1.43 M (10% v/v) 2-mercaptoethanol (2-ME). Treating with 2-ME caused 100% (15/15) of the samples to become IgM negative.
Sera Freeze-Thaw Study
Focus (Study Site 4) assessed the impact on the WNV IgM assay's reactivity by selecting 8 sera (5 positive and 3 negative), subjecting them to up to 5 repeated freeze-thaw cycles, and testing them in parallel with aliquots that had not been frozen. There were no changes in interpretation in any of the sera. Positive samples trended slightly towards increasing indices, while negative sera did not appear to change.
Reproducibility
Reproducibility studies included Inter-lot Reproducibility, Inter/Intra-assay Reproducibility, and Inter-laboratory Reproducibility. In each study, two sets of samples were masked duplicates. Focus (Study Site 4) assessed the device's Inter-lot Reproducibility by testing five samples on three separate lots. For one lot. For one lot. the samples were run in triplicate, and run in duplicate with the other two lots. Each of the three lots had a different lot of Antigen and Capture Wells. Focus (Study Site 4) assessed the device's Inter/Intra-assay Reproducibility by testing seven samples in triplicate, once a day, for three days, for a total of 63 data points. A state department of health laboratory located in the northeastern U.S. (Study Site 1), a clinical laboratory located in the mid-western U.S. (Study Site 2), and Focus (Study Site 4), assessed the device's Inter-laboratory Reproducibility. Each of the three laboratories in triplicate on three different days.
| Sample | Inter- & Intra-assay | Inter-lot | Inter-Lab | ||||
|---|---|---|---|---|---|---|---|
| IndexMean | Intra-assay%CV | Inter-assay%CV | IndexMean | Index%CV | IndexMean | Index%CV | |
| M2* | 0.21 | 2.9 | 10.3 | 0.22 | 1.2 | 0.23 | 9.7 |
| M6* | 0.23 | 3.4 | 20.0 | 0.23 | 0.4 | 0.24 | 13.2 |
| M5 | 0.69 | 1.6 | 5.7 | 0.70 | 0.7 | 0.71 | 6.4 |
| M1* | 1.43 | 1.5 | 2.9 | 1.41 | 2.6 | 1.45 | 4.0 |
| M7* | 1.53 | 1.8 | 4.0 | 1.54 | 2.1 | 1.49 | 12.8 |
| M3 | 2.37 | 2.7 | 1.7 | 2.33 | 3.6 | 2.23 | 2.5 |
| M4 | 2.99 | 1.9 | 0.3 | 2.98 | 1.9 | 2.78 | 2.3 |
re du ~iktlitz
- There were two sets of masked pairs (same sample, different labeled identity): M2 & M6 were one masked pair, and M1 & M7 were the second masked pair.
{8}------------------------------------------------
| 510(k) Number (if known): | K040854 |
|---|---|
| Device Name: | West Nile Virus IgM Capture ELISA |
| Indications for Use: | The Focus Technologies West Nile Virus IgM Capture ELISA isintended for qualitatively detecting IgM antibodies to West Nilevirus in human serum. In conjunction with the Focus TechnologiesWest Nile Virus ELISA IgG, the test is indicated for testingpersons having symptoms of meningioencephalitis, as an aid in thepresumptive laboratory diagnosis of West Nile virus infection.Positive results must be tested using the background subtractionmethod (either on the initial test or on a repeat test). Positiveresults must be confirmed by neutralization test, or by using thecurrent CDC guidelines for diagnosing West Nile encephalitis.This test is not intended for self-testing, and this test is not FDAcleared nor approved for testing blood or plasma donors. Assayperformance characteristics have not been established forautomated instruments. |
Prescription Use _ X (Part 21 CFR 801 Subpart D)
AND/OR
Over-the-Counter Use (21 CFR 807 Subpart C)
(PLEASE DO NOT WRITE BELOW THIS LINE CONTINUE ON ANOTHER PAGE IF NEEDED)
Concurrence of CDRH, Office of In Vitro Diagnostic Devices (OIVD)
{9}------------------------------------------------
DEPARTMENT OF HEALTH & HUMAN SERVICES
Public Health Service
Image /page/9/Picture/2 description: The image shows the logo for the U.S. Department of Health & Human Services. The logo consists of a circular seal with the text "DEPARTMENT OF HEALTH & HUMAN SERVICES U.S.A." arranged around the perimeter. Inside the circle is an abstract symbol that resembles a stylized caduceus or a bird in flight, composed of three curved lines.
JUN 3 0 2004
Food and Drug Administration 2098 Gaither Road Rockville MD 20850
Michael J. Wagner, Esq. Senior Regulatory Affairs Specialist Focus Technologies, Inc. 10703 Progress Way Cypress, CA 90630
K040854 Re:
Trade/Device Name: Focus West Nile Virus IgM Capture ELISA Regulation Number: 21 CFR 866.3940 Regulation Name: West Nile Virus Serological Reagents Regulatory Class: Class II Product Code: NOP Dated: June 6, 2004 Received: June 8, 2004
Dear Mr. Wagner:
We have reviewed your Section 510(k) premarket notification of intent to market the device referenced above and have determined the device is substantially equivalent (for the indications for use stated in the enclosure) to legally marketed predicate devices marketed in interstate commerce prior to May 28, 1976, the enactment date of the Medical Device Amendments, or to devices that have been reclassified in accordance with the provisions of the Federal Food, Drug, and Cosmetic Act (Act) that do not require approval of a premarket approval application (PMA). You may, therefore, market the device, subject to the general controls provisions of the Act. The general controls provisions of the Act include requirements for annual registration, listing of devices, good manufacturing practice, labeling, and prohibitions against misbranding and adulteration.
If your device is classified (see above) into either class II (Special Controls) or class III (PMA), it may be subject to such additional controls. Existing major regulations affecting your device can be found in Title 21, Code of Federal Regulations (CFR), Parts 800 to 895. In addition, FDA may publish further announcements concerning your device in the Federal Register.
Please be advised that FDA's issuance of a substantial equivalence determination does not mean that FDA has made a determination that your device complies with other requirements of the Act or any Federal statutes and regulations administered by other Federal agencies. You must comply with all the Act's requirements, including, but not limited to: registration and listing (21 CFR Part 807); labeling (21 CFR Parts 801 and 809); and good manufacturing practice requirements as set forth in the quality systems (QS) regulation (21 CFR Part 820).
{10}------------------------------------------------
Page 2
This letter will allow you to begin marketing your device as described in your Section 510/k) premarket notification. The FDA finding of substantial equivalence of your device to a legally marketed predicate device results in a classification for your device and thus, permits your device to proceed to the market.
If you desire specific information about the application of labeling requirements to your device, or questions on the promotion and advertising of your device, please contact the Office of In Vitro Diagnostic Device Evaluation and Safety at (301) 594-3084. Also, please note the regulation entitled. "Misbranding by reference to premarket notification" (21CFR Part 807.97). You may obtain other general information on your responsibilities under the Act from the Division of Small Manufacturers, International and Consumer Assistance at its toll-free number (800) 638-2041 or (301) 443-6597 or at its Internet address http://www.fda.gov/cdrh/dsma/dsmamain.html.
Sincerely yours,
Salazar
Sally A. Hojvat, M.Sc., Ph.D. Director Division of Microbiology Devices Office of In Vitro Diagnostic Device Evaluation and Safety Center for Devices and Radiological Health
Enclosure
{11}------------------------------------------------
Indications for Use
510(k) Number (if known):K040854
Device Name: Focus West Nile Virus IgM Capture ELISA
Indications For Use: The Focus Technologies West Nile Virus IgM Capture ELISA is intended for qualitatively detecting IgM antibodies to West Nile virus in human serum. In conjunction with the Focus Technologies West Nile Virus ELISA IgG, the test is indicated for testing persons having symptoms of meningioencephalitis, as an aid in the presumptive laboratory diagnosis of West Nile virus infection. Positive results must be tested using the background subtraction method (either on the initial test or on a repeat test). Positive results must be confirmed by neutralization test, or by using the current CDC quidelines for diagnosing West Nile encephalitis. This test is not intended for selftesting, and this test is not FDA cleared nor approved for testing blood or plasma donors. Assay performance characteristics have not been established for automated instruments.
Prescription Use
(Part 21 CFR 801 Subpart D)
AND/OR
Over-The-Counter Use (21 CFR 801 Subpart C)
(PLEASE DO NOT WRITE BELOW THIS LINE-CONTINUE ON ANOTHER PAGE IF NEEDED)
Concurrence of CDRH, Office of Device Evaluation (ODE)
Saga Atto 6/23/04
Division Sign-Off
Office of In Vitro Diagnostic Device Evaluation and Safety
KO40854 510(k) _
Page 1 of
§ 866.3940 West Nile virus serological reagents.
(a)
Identification. West Nile virus serological reagents are devices that consist of antigens and antisera for the detection of anti-West Nile virus IgM antibodies, in human serum, from individuals who have signs and symptoms consistent with viral meningitis/encephalitis. The detection aids in the clinical laboratory diagnosis of viral meningitis/encephalitis caused by West Nile virus.(b)
Classification. Class II (special controls). The special control is FDA's guidance entitled “Class II Special Controls Guidance Document: Serological Reagents for the Laboratory Diagnosis of West Nile Virus.” See § 866.1(e) for the availability of this guidance document.