The Focus Technologies West Nile Virus ELISA IgG is intended for qualitatively detecting IgG antibodies to West Nile virus in human serum. In conjunction with the Focus Technologies West Nile Virus IgM Capture ELISA, 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 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.

Device Description

Indirect Enzyme-linked immunosorbent assay for qualitatively detecting human serum IgG antibodies to West Nile virus.

AI/ML Overview

Here's a detailed breakdown of the acceptance criteria and the study that proves the Focus Technologies West Nile Virus ELISA IgG device meets them, based on the provided text:

Acceptance Criteria and Device Performance for Focus Technologies West Nile Virus ELISA IgG

The document does not explicitly state pre-defined acceptance criteria (e.g., "sensitivity must be > X%") for the device. Instead, it reports the device's performance characteristics from various studies. Therefore, the "acceptance criteria" presented below are inferred from the reported performance, implying that these levels of performance were deemed acceptable for market clearance.

1. Table of Acceptance Criteria (Inferred) and Reported Device Performance

Performance Metric	Inferred Acceptance Criterion (Implicit)	Reported Device Performance	Study Site/Details
Clinical Sensitivity (confirmed WNV encephalitis)	High sensitivity for confirmed WNV encephalitis patients.	97.3% (36/37)	Study Site 1: Encephalitis/Meningitis Patients (n=300); confirmed by CDC WNV IgG ELISA & WNV PRNT.
Positive Agreement with Presumptive CDC WNV IgG ELISA	High positive agreement with presumptive CDC WNV IgG ELISA for specific flavivirus cases.	100% (5/5)	Study Site 1: Encephalitis/Meningitis Patients (n=300); presumptive positive.
Negative Agreement with Presumptive CDC WNV IgG ELISA	High negative agreement with presumptive CDC WNV IgG ELISA for negative cases.	99.0% (203/205)	Study Site 1: Encephalitis/Meningitis Patients (n=300); presumptive negative.
Serological Sensitivity (WNV PRNT positive)	Adequate sensitivity for WNV PRNT positive samples. (Note: The reported value of 36% is notably lower than clinical sensitivity, suggesting different populations or infection stages).	36.0% (27/75)	Study Site 2: WNV PRNT Positives (n=75); sera screened positive by Focus native antigen ELISA and confirmed by PRNT.
Negative Agreement with Presumptive WNV IFA	High negative agreement with WNV IgG IFA negative samples.	95.6% (152/157)	Study Site 3: WNV IFA Negatives (n=157).
Serological Sensitivity (CDC IgG ELISA positive & WNV PRNT positive)	100% (for very limited sample size).	100% (1/1)	Study Site 4: Suspected Encephalitis/Meningitis Patients (n=50); 1 confirmed positive by WNV PRNT.
Negative Agreement with Presumptive CDC IgG ELISA (WNV negative)	High negative agreement for WNV negative samples.	95.9% (47/49)	Study Site 4: Suspected Encephalitis/Meningitis Patients (n=50); 49 presumptively negative for arboviruses by CDC ELISA.
Positive Agreement with Presumptive CDC IgG ELISA (Non-Flavivirus Test Samples)	High positive agreement with CDC ELISA positive samples in a general population.	100% (21/21)	Study Site 4: Non-Flavivirus Test Samples (n=476); positive samples confirmed by CDC WNV IgG ELISA.
Negative Agreement with Presumptive CDC IgG ELISA (Non-Flavivirus Test Samples)	High negative agreement with CDC ELISA negative samples in a general population.	96.8% (426/440)	Study Site 4: Non-Flavivirus Test Samples (n=476); negative samples confirmed by CDC WNV IgG ELISA.
Cross-reactivity	Acceptable levels of cross-reactivity with other flaviviruses and common infections, with clear reporting of positive rates.	Varies: e.g., Dengue (95%), Japanese encephalitis (30%), St. Louis encephalitis (57.1%), Yellow fever (45%). Lower for Alphavirus (11.8%), Bunyavirus (20%), HSV-1 (8.3%), EBV (8.3%), CMV (20%), Echovirus/Poliovirus (10%), Lyme (15%).	Study Site 4 & 1; various populations (n=75) with sero-positive results for specified pathogens.
Freeze-Thaw Stability	No change in interpretation after multiple freeze-thaw cycles.	No changes in interpretation (for 5 positive, 3 negative samples after up to 5 cycles).	Focus (Study Site 4); 8 sera subjected to up to 5 freeze-thaw cycles.
Reproducibility (Inter-lot, Inter/Intra-assay, Inter-laboratory)	Consistent results across lots, within and between assays, and across different laboratories, indicated by acceptable %CV.	Inter- & Intra-assay %CV: 1.0-21.2%; Inter-lot %CV: 4.1-13.1%; Inter-Lab %CV: 11.0-22.3%.	Multiple sites (Study Sites 1, 2, 4); various setups (triplicates, duplicates, 3 days).

2. Sample Size Used for the Test Set and Data Provenance

Study Site 1 (Encephalitis/Meningitis Patients):
- Sample Size: 300 total patients (37 confirmed positive, 210 presumptive results, 53 unclassified). Performance calculated on 242 samples (37 confirmed positive + 205 presumptive negative).
- Data Provenance: Sera were sequentially submitted to a state department of health laboratory in the northeastern U.S., archived, and masked. Retrospective.
Study Site 2 (WNV PRNT Positives):
- Sample Size: 75 retrospective sera.
- Data Provenance: Sera were sequentially submitted to a clinical laboratory in the mid-western U.S., archived. Retrospective.
Study Site 3 (WNV IFA Negatives):
- Sample Size: 157 samples.
- Data Provenance: Retrospective sera from a clinical laboratory in the southwestern U.S.
Study Site 4 (Suspected Encephalitis/Meningitis Patients):
- Sample Size: 50 sera (1 confirmed positive, 49 presumptively negative).
- Data Provenance: Retrospective and masked sera provided by a U.S. federal government laboratory.
Study Site 4 (Non-Flavivirus Test Samples):
- Sample Size: 476 samples. Performance calculated on 461 samples (21 CDC ELISA positive + 440 CDC ELISA negative).
- Data Provenance: Prospectively collected from North America (August 2003) and submitted to a clinical laboratory in Southern California for non-flavivirus tests. Prospective, but the "test set" for WNV performance was created using the CDC ELISA.
Cross-reactivity Studies:
- Sample Size: 75 sera (20 Dengue, 20 Japanese encephalitis, 21 St. Louis encephalitis, 20 Yellow fever, 17 Alphavirus, 15 Bunyavirus, 60 HSV-1, 12 EBV, 20 Cytomegalovirus, 20 Echovirus/Poliovirus, 20 Lyme disease).
- Data Provenance: Sera were archived and masked, conducted at Focus (Study Site 4, for most pathogens) and a state department of health laboratory in the northeastern U.S. (DOH, for SLE positives). Retrospective.
Freeze-Thaw Study:
- Sample Size: 8 sera (5 positive, 3 negative).
- Data Provenance: Conducted at Focus (Study Site 4).
Reproducibility Studies:
- Sample Size: Inter-lot: 5 samples; Inter/Intra-assay: 7 samples; Inter-laboratory: 7 samples.
- Data Provenance: Conducted at Focus (Study Site 4), a state department of health laboratory in the northeastern U.S. (Study Site 1), and a clinical laboratory in the mid-western U.S. (Study Site 2).

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Their Qualifications

The document does not explicitly state the "number of experts" or their "qualifications" involved in establishing the ground truth. However, it indicates:

Reference Methods Used:
- CDC West Nile Virus IgG Capture ELISA
- Plaque Reduction Neutralization Test (PRNT) for West Nile virus
- Dengue PRNT
- St. Louis Encephalitis (SLE) PRNT
- West Nile Virus native antigen ELISA
- West Nile IFA

These are established laboratory assays, and their results are considered the "ground truth." The implication is that skilled laboratory personnel at the respective state, federal, and clinical laboratories performed these reference tests. The qualifications of these individuals (e.g., highly trained lab technologists, clinical microbiologists) are inherent to the operation of such labs but are not specified in terms of "years of experience" or "radiologist" equivalent, as this is an in vitro diagnostic device.

4. Adjudication Method for the Test Set

The document does not describe an explicit "adjudication method" in the sense of multiple experts independently evaluating cases and resolving discrepancies (e.g., 2+1, 3+1).

Instead, the "ground truth" was established by reference laboratory assays (CDC WNV IgG ELISA, PRNT, IFA), which inherently have their own established protocols for result interpretation. For example, "confirmed positive West Nile encephalitis patients" were defined by symptoms and positive results from both CDC WNV IgG ELISA and WNV PRNT. Equivocal or indeterminant results from reference assays were often excluded from performance calculations.

5. If a Multi Reader Multi Case (MRMC) Comparative Effectiveness Study Was Done

No, a Multi Reader Multi Case (MRMC) comparative effectiveness study was not done. This type of study typically involves comparing human reader performance with and without an AI-assisted device in diagnostic imaging contexts. The Focus Technologies West Nile Virus ELISA IgG is an in vitro diagnostic laboratory test, not an imaging device intended for human interpretation.

6. If a Standalone (Algorithm Only Without Human-in-the-Loop Performance) Was Done

Yes, the studies conducted evaluated the standalone performance of the Focus Technologies West Nile Virus ELISA IgG device (an algorithm/assay only). The device itself is an indirect ELISA designed to qualitatively detect antibodies, implying that the interpretation of the optical density readings and the final result (positive, negative, equivocal) is performed by the device's internal algorithms or by comparison to defined cut-offs, without a "human-in-the-loop" decision support role in the sense of AI for image interpretation. The performance metrics presented (sensitivity, specificity/agreement) directly reflect the device's ability to classify samples based on its own output against established reference methods.

7. The Type of Ground Truth Used

The primary types of ground truth used were:

Reference Laboratory Assay Results:
- CDC West Nile Virus IgG Capture ELISA: A highly respected and commonly used reference method for WNV IgG.
- Plaque Reduction Neutralization Test (PRNT): Considered the gold standard for serological confirmation of arbovirus infections due to its high specificity.
- West Nile IFA (Immunofluorescence Assay): Another serological test.
- Dengue PRNT, SLE PRNT: Used for cross-reactivity assessment.
- West Nile virus native antigen ELISA: Used as a screening method in Study Site 2 before PRNT confirmation.
Clinical Criteria: For Study Site 1 and 4, patient presentation (meningioencephalitis symptoms, fever, altered mental status, CSF findings) was combined with laboratory results to define confirmed cases.

This combination of highly specific and sensitive reference assays, often coupled with relevant clinical symptoms, provides a robust ground truth for an in vitro diagnostic device.

8. The Sample Size for the Training Set

The document does not explicitly mention a "training set" in the context of machine learning or AI development. This device is an ELISA, which is typically a biochemically-based assay, not an AI/ML algorithm that requires a separate training phase with labeled data in the same way. The performance studies evaluate the assay's built characteristics against clinical samples and reference methods.

If one were to loosely interpret "training" as the internal development and calibration of the assay (e.g., setting cut-offs), the size of the samples used for that purpose is not detailed. The provided studies are primarily for performance validation.

9. How the Ground Truth for the Training Set Was Established

As noted above, there isn't a "training set" in the AI/ML sense for this ELISA device. The concept of "ground truth" for the internal development and establishment of assay cut-offs would typically involve:

Well-characterized panels: Samples from individuals with known WNV infection status (confirmed by PRNT or PCR) and known negative individuals.
Titration and statistical analysis: To determine optimal cut-off values for distinguishing positive, negative, and equivocal results based on optical density readings.

However, the document focuses on the validation studies performed to demonstrate the device's performance against established reference methods and clinical populations, rather than detailing its initial development and calibration.

Summary

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OCT 2 2 2003

Image /page/0/Picture/1 description: The image shows the logo for Focus Technologies. The logo consists of the word "FOCUS" in a bold, sans-serif font, with two crescent moon shapes forming the letter "O". Below the word "FOCUS" is the word "technologies" in a smaller, sans-serif font. The logo is black and white.

031953

Applicant	Focus Technologies, Inc.10703 Progress WayCypress, California 90630USA
EstablishmentRegistration No.	2023365
Contact Person	Michael J. Wagner, Esq.tel (714) 220-1900fax (714) 995-6921mwagner@focustechnologies.com
Summary Date	October 17, 2003
Proprietary Name	West Nile Virus ELISA IgG
Generic Name	West Nile Virus ELISA IgG
Classification	West Nile Virus Serological Reagents21 CFR §866.3940Class II
Predicate Device	Focus Technologies Arbovirus IFA IgG (K913617)Focus Technologies HSV-2 ELISA (K993724)CDC West Nile Virus IgG ELISAWest Nile Virus Plaque Reduction Neutralization Test

Device Description

Indirect Enzyme-linked immunosorbent assay for qualitatively detecting human serum IgG antibodies to West Nile virus.

Intended Use

Test Principle

In the Focus Technologies West Nile Virus ELISA IgG assay, the polystyrene microwells are coated with recombinant West Nile virus antigen. Diluted serum samples and controls are incubated in the wells to allow anti-WNV IgG antibody (if present in the sample) to react with the antigen. Nonspecific reactants are removed by washing and peroxidaseconjugated anti-human IgG is added that reacts with human IgG bound to the antigen. 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 quantified by a spectrophotometric reading of optical density readings are compared with reference cut-off OD readings to determine results.

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K031953 510(k) Summary of Safety and Effectiveness West Nile Virus ELISA IgG Catalog No. EL0300G Prepared October 17, 2003

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% samples from persons of unspecified gender.

Age	Neg	Eqv	Pos	% Positive	95%CI
0 to 9	20	0	4	16.7% (4/24)	4.7-37.4%
10 to 19	25	2	2	6.9% (2/29)	0.9-22.8%
20 to 29	63	4	3	4.3% (3/70)	0.9-12.0%
30 to 39	76	1	5	6.1% (5/82)	2.0-13.7%
40 to 49	69	1	8	10.3% (8/78)	4.5-19.2%
50 to 59	47	1	3	5.9% (3/51)	1.2-16.2%
60 to 69	32	1	6	15.4% (6/39)	5.9-30.5%
70 to 79	28	1	5	14.7% (5/34)	5.0-31.1%
80+	15	1	2	11.1% (2/18)	1.4-34.7%
Unknown	41	2	8	15.7% (8/51)	7.0-28.6%
Overall	416	14	46	9.7% (46/476)	7.2-12.7

IgG Prevalence with Samples Submitted for Non-Flavivirus Testing(n = 476)

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K031953

Performance Characteristics

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 encephalitis or viral meningitis.

Viral encephalitis criteria included:

1. fever:
1. altered mental status and/or other evidence of cortical involvement; and
1. CSF pleocytosis with predominant lymphocytes and/or elevated protein and a negative gram stain and culture.

Viral meningitis criteria included:

1. fever:
1. headache, stiff neck and/or other meningeal signs; and
1. CSF pleocytosis with predominant lymphocytes and/or elevated protein and a negative gram stain and culture). The sera were sequentially submitted to the laboratory, archived, and masked. The reference methods were CDC WNV IgG Capture ELISA, and plaque reduction neutralization test (PRNT) for West Nile virus.

Of 300 encephalitis/meningitis patients, 37 patients were classified as confirmed positive West Nile encephalitis patients (meningioencephalitis symptoms, CDC WNV IgG ELISA positive, and WNV PRNT positive), 210 patients had presumptive assay (CDC WNV IgG ELISA) results, and 53 patients were unclassified because the CDC WNV IgG ELISA results were indeterminant or equivocal. The Focus IgG ELISA was positive with 97.3% (36/37) of the confirmed positive WNV encephalitis patients (including 1 Focus equivocal calculated as negative). Of the 210 patients with presumptive assay results, 4 were classified as presumed positive flavivirus encephalitis patients (CDC WNV IgG positive, PRNT negative), one was classified as a confirmed dengue positive (CDC WNV IgG ELISA positive, dengue PRNT positive), and 205 were classified as presumed negative patients (CDC WNV IgG ELISA negative). The Focus IgG ELISA was positive with 100% (4/4) of the presumed positive WNV encephalitis patients, and positive with the one dengue positive patient. The Focus IgG ELISA was negative with 99.0% (203/205) of the presumed negative patients (including 1 Focus equivocal calculated as positive). The 53 unclassified patients were excluded from the calculations

Study Site 1: Focus Reactivity with Encephalitis/Meningitis Patients (n = 300)*

Specimens Characterized by Reference Assays		Focus WNV IgG ELISA Results
	Neg	Eqv	Pos	Total	%	95%CI
Clinical sensitivity (encephalitis or /meningitis symptoms, CDC WNV IgG ELISA positive and WNV PRNT positive)	0	1	36	37	97.3% (36/37)	85.8-99.9%
Positive agreement with presumptive CDC WNV IgG ELISA †	0	0	5	5	100% (5/5)	47.8-100%
Negative agreement with presumptive CDC WNV IgG ELISA negative	203	1	1	205	99.0% (203/205)	96.5-99.9%

*Excluding 53 CDC IgG ELISA results (49 indeterminant and 4 equivocal samples).

f One of the presumptive samples was dengue PRNT positive and the other 4 presumptive positives were negative with WNV, dengue and SLE PRNT.

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K031953

Page 4 of 6

Performance Characteristics (continued)

Study Site 2: Focus Reactivity with WNV PRNT Positives (n = 75)

A clinical laboratory located in the mid-western U.S. assessed the device's reactivity with 75 retrospective sere that were screened positive (by Focus) with a West Nile virus native antigen ELISA, and confirmed West Nile positive by plaque reduction neutralization test (PRNT). The sera were sequentially submitted to the laboratory, archived, The Focus IgG ELISA was positive with 36.0% (27/75) of the 75 PRNT positives (calculating 4 equivocals as negative), equivocal with four samples, and negative with 44 samples.

Study Site 2: Focus Reactivity with WNV PRNT Positives (n = 75)
Specimens Characterized by Reference Assays	Focus WNV IgG ELISA Results
	Neg	Eqv	Pos	Total	%	95%CI
Serological sensitivity (WNV PRNT positive)	44	4	27	75	36.0% (27/75)	25.2-92.3%

Study Site 3: Focus Reactivity with West Nile IFA Negatives (n=157)

A clinical laboratory located in the southwestern U.S. assessed reactive West Nile IFA negative samples. The Focus IgG ELISA was 96.8% (152/157) negative with WNV IgG IFA negative samples (including two equivocals calculated as positive), and positive with three samples.

Study Site 3: Focus Reactivity with West Nile IFA Negatives (n=157)

Specimens Characterized by Reference Assays	Focus WNV IgG ELISA Results
	Neg	Eqv	Pos	Total	%	95% CI
Negative agreement with presumptive WNV IFA	152	2	3	157	95.6% (152/157)	91.1-98.2%

Study Site 4: Focus Reactivity with Suspected Encephalitis/Meningitis Patients (n = 50)

Focus assessed the device's reactivity with 50 sera from patients suspected of encephalitis/meningitis. A U.S. federal government laboratory provided the retrospective and masked sera. One sample was confirmed positive by West Nile PRNT, and the other 49 were presumptively negative (CDC ELISA) for arboviruses present in North America (LAC, EEE, SLE and WNV). The Focus IgG ELISA was negative with 95.6% (47/49) of the WNV negative samples, and positive with the one positive confirmed by West Nile PRNT .

Study Site 4: Focus Reactivity with Suspected Encephalitis/Meningitis Patients (n = 50)

Specimens Characterized by Reference Assays	Focus WNV IgG ELISA Results
	Neg	Eqv	Pos	Total	%	95% CI
Serological sensitivity (CDC IgG ELISA positive andWNV PRNT positive)	0	0	1	1	100% (1/1)	NA
Negative agreement with presumptive CDC IgG ELISA	47	0	2	49	95.9% (47/49)	86.0-99.5%

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K031953

510(k) Summary of Safety and Effectiveness West Nile Virus ELISA IgG Catalog No. EL0300G Prepared October 17, 2003

Page 5 of 6

Performance Characteristics (continued)

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 non-flavivirus tests (e.g., test for other infectious diseases). Positive samples were tested with a CDC West Nile IgG ELISA. The Focus West Nile ELISA IgG was negative with 96.8% (426/440) of the CDC ELISA negative samples (including 14 Focus equivocals calculated as positive), and was positive with 100% (21/21) of the CDC ELISA positive samples. Fifteen CDC ELISA IgG indeterminant samples were excluded from performance calculations.

Study Site 4: Focus Reactivity with Non-Flavivirus Test Samples (n = 476)*

Specimens Characterized by Reference Assays	Focus WNV IgG ELISA Results
	Neg	Eqv	Pos	Total	%	95% CI
Positive agreement with presumptive CDC IgG ELISA	0	0	21	21	100% (21/21)	83.9-100%
Negative agreement with presumptive CDC IgG ELISA	426	14	0	440	96.8% (426/440)	94.7-98.3%

Excludes 15 CDC IgG ELISA indeterminant samples.

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 archived and masked. The results of the study are summarized in the table below.

Focus Cross-reactivity
Population	Site	Neg	Eqv	Pos	Total	% Positive	95% CI
Dengue virus (secondary infections)	4	1	0	19	20	95.0% (19/20)	75.1-99.9%
Japanese encephalitis virus	4	14	3	3	20	30.0% (6/20)	11.9-54.3%
St. Louis encephalitis virus	1	8	1	11	21	57.1% (12/21)	34.0-78.2%
Yellow fever virus	4	11	4	5	20	45.0% (9/20)	23.1-68.5%
Alphavirus (Sindbis & Eastern equine viruses)	4	15	0	2	17	11.8% (2/17)	0.1-36.4%
Bunyavirus (Jamestown Canyon & La Crosse)	1	12	2	1	15	20.0% (3/15)	4.3-48.1%
Herpes simplex virus type 1	4	55	0	5	60	8.3% (5/60)	2.8-18.4%
Epstein-Barr virus	4	11	0	1	12	8.3% (1/12)	0.2-38.5%
Cytomegalovirus	4	16	0	4	20	20.0% (4/20)	5.7-43.7%
Echovirus/Poliovirus	4	18	1	1	20	10.0% (2/20)	1.2-31.7%
Borrelia burgdorferi (Lyme disease)	4	17	1	2	20	15.0% (3/20)	3.2-37.9%

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Performance Characteristics (continued)

Focus Sample Freeze-Thaw Study

Focus (Study Site 4) assessed the impact on the WNV IgG 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 alluots that had not been frozen. There were no changes in interpretation in any of the sera. Positive samples in the IgM ELISA trended slightly towards increasing indices, while negative samples in the IgG ELISA did not appear to change indices.

Focus Reproducibility

Reproducibility studies included Inter-lot Reproducibility, InterlIntra-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. 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), and a clinical laboratory located in the mid-western U.S. (Study Site 2), Focus (Study .Site 4), assessed the device's Inter-laboratory Reproducibility. Each of the three laboratories tested seven samples in triplicate on three different days.

Sample	Inter- & Intra-assay			Inter-lot		Inter-Lab
	Index Mean	Intra-assay %CV	Inter-assay %CV	Index Mean	Index %CV	Index Mean	Index %CV
G6*	0.23	12.2	18.2	0.30	13.1	0.32	11.0
G2*	0.29	21.2	17.3	0.34	7.5	0.35	22.3
G5	0.65	7.9	21.3	0.73	7.2	0.69	19.0
G7*	1.14	3.5	18.2	1.30	5.7	1.21	14.1
G1*	1.22	3.2	17.1	1.36	7.0	1.25	16.4
G4	2.44	1.0	16.2	2.79	4.1	2.47	12.8
G3	2.98	3.9	17.3	3.37	4.1	3.10	12.6

Foous Donroducibility

There were two sets of masked pairs (same sample, different labeled identity): C2 & G6 were the second masked pair.

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DEPARTMENT OF HEALTH & HUMAN SERVICES

Image /page/6/Picture/1 description: The image shows the logo for the U.S. Department of Health & Human Services. The logo consists of a stylized caduceus, which is a symbol often associated with medicine and healthcare. The words "DEPARTMENT OF HEALTH & HUMAN SERVICES USA" are arranged in a circular pattern around the caduceus.

Public Health Service

Food and Drug Administration 2098 Gaither Road Rockville MD 20850

OCT 2 2 2003

Michael J. Wagner, Esq. Senior Regulatory Affairs Specialist Focus Technologies, Inc. 10703 Progress Way Cypress, CA 90630

Re: K031953

Trade/Device Name: West Nile Virus ELISA IgG Regulation Number: 21 CFR 866.3940 Regulation Name: West Nile Virus Serological Reagents Regulatory Class: Class II Product Code: NOP Dated: October 17, 2003 Received: October 20, 2003

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 Mav 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. Iisting 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 (OS) regulation (21 CFR Part 820).

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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). Other general information on your responsibilities under the Act may be obtained 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,

Steven Sutman

Steven I. Gutman, M.D., M.B.A. Director Office of In Vitro Diagnostic Device Evaluation and Safety Center for Devices and Radiological Health

Enclosure

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510(k) Number (if known): K031953

Device Name:

West Nile Virus ELISA IgG

The Focus Technologies West Nile Virus ELISA IgG is intended Indications for Use: for qualitatively detecting IgG antibodies to West Nile virus in human serum. In conjunction with the Focus Technologies West Nile Virus IgM Capture ELISA, 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 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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Soyattyns 10/21/03
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Regulation Number and Section

§ 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.