(148 days)
The ZIKV Detect 2.0 IgM Capture ELISA is intended for the qualitative detection of Zika virus IgM antibodies in human sera for the presumptive clinical laboratory diagnosis of Zika virus infection. The assay is intended for use only in patients with clinical signs and symptoms consistent with Zika virus infection, and/or CDC Zika virus epidemiological criteria (e.g., history of residence in or travel to a geographic region with active Zika transmission at the time of travel, or other epidemiological criteria for which Zika virus testing may be indicated). Assay results are for the presumptive detection of IgM antibodies to Zika virus (ZIKV). Positive results must be confirmed by following the latest CDC guidelines for the diagnosis of Zika virus infection.
Results of this test are intended to be used in conjunction with clinical observations. patient history, epidemiological information, and other laboratory evidence to make patient management decisions. Zika IgM levels are variable over the course of the infection, and may be detectable near day four post onset of symptoms and persist up to approximately 12 weeks following initial infection.
Negative results may be seen in specimens collected before day four post onset of symptoms or after the window of detectable IgM closes, and therefore do not preclude the possibility of Zika virus infection, past or present.
This assay is not indicated for testing blood or plasma donors.
The ZIKV Detect IgM Capture ELISA is a sandwich-type immunoassay. The test kit includes microtiter wells coated with anti-human IgM antibodies, ZIKV IgM Negative, and IgM Positive controls, ZIKV Sample Dilution Buffer, ZIKV Recombinant Antigen (Zika Ag) for IgM, Cross-reactive Control Antigen (CCA) for ZIKV IgM and normal cell antigens (NCA), secondary antibodies targeting the flavivirus antigens. The test kit also contains a HRPlabeled ZIK V-specific monoclonal antibody and tetramethylbenzidine (TMB) substrate which are used to detect ZIKV IgM antibodies in the wells.
The ZIKV Detect 2.0 IgM Capture ELISA contains sufficient reagents for one plate of 96 wells (12 x 8 strips) for human IgM targeting Zika virus. This is sufficient for testing a maximum of 28 unknown samples for human IgM, with controls included in duplicate.
Here's a breakdown of the acceptance criteria and the study details for the ZIKV Detect 2.0 IgM Capture ELISA, based on the provided text:
1. Acceptance Criteria and Reported Device Performance
The provided text doesn't explicitly state "acceptance criteria" in a separate section with specific numerical targets like "Sensitivity > X%" or "Specificity > Y%." However, from the "Performance Characteristics" and "Clinical Studies" sections, we can infer the expected performance and compare it with the reported results. The FDA's conclusion that the device's information is "sufficient" to classify it implies that the presented performance met their internal, unstated acceptance criteria for a class II device with special controls.
Here's an inferred table based on the provided results:
| Acceptance Criterion (Inferred from study outcomes) | Reported Device Performance (ZIKV Detect 2.0 IgM Capture ELISA) |
|---|---|
| Analytical Performance | |
| Reproducibility (Total Precision %CV of ISR) | Low Positive: 29.6% |
| Moderate Positive: 25.8% | |
| Re-test: 22.7% | |
| Negative: 13.0% | |
| High Negative: 16.1% | |
| (Range: 13.0% - 29.6% depending on sample) | |
| Limit of Detection (LOD) | 225 IU/mL (WHO 1st International Standard for anti-Asian lineage Zika virus antibody, human) |
| Analytical Specificity (Cross-reactivity) | Dengue: 1/39 Zika Positive, 38/39 Other Flavivirus Positive |
| West Nile Virus: 2/28 Zika Positive, 19/28 Other Flavivirus Positive | |
| (Overall shows some cross-reactivity, but also differentiation to "Other Flavivirus Positive") | |
| Interfering Substances | Very high HAMA (798.7 ng/mL) caused interference (false negatives, 3/3 low reactive samples). Other substances (Bilirubin, Hemoglobin, Albumin, Cholesterol, Triglycerides, lower HAMA, RF) showed no observed interference. |
| IgM Class Specificity | All Zika positive samples tested negative after 5mM DTT treatment, indicating IgM specificity. |
| Freeze-Thaw Stability | Stable for a maximum of three freeze-thaw cycles. |
| Clinical Performance (Endemic Subjects) | PPA: 89.4% (84/94); 95% CI: 81.3%-94.8% |
| NPA: 99.2% (257/259); 95% CI: 97.2%-99.9% | |
| Clinical Performance (Non-Endemic Subjects) | PPA: 81.3% (13/16); 95% CI: 54.4%-96.0% |
| NPA: 95.8% (230/240); 95% CI: 92.5%-98.0% | |
| Clinical Performance (FDA Panel - Zika IgM Consensus) | PPA: 100% (24/24) |
| NPA: 100% (12/12) | |
| Clinical Performance (FDA Panel - Cross-reactivity) | West Nile (n=10): 1 False Positive (Zika), 1 False Negative (Zika), 8 Correct Call (Other Flavivirus) |
| Dengue (n=10): 0 False Positive (Zika), 6 False Negative (Zika), 4 Correct Call (Other Flavivirus) |
2. Sample Size Used for the Test Set and Data Provenance
-
Analytical Reproducibility Study:
- Test Set Sample Size: 5 panel members (negative, high negative, low positive, moderate positive, re-test specimen). Each panel member had 270 replicates (3 replicates x 3 sites x 2 operators x 5 days x 3 kit lots / 3 kit lots). So, essentially 5 samples were tested extensively.
- Data Provenance: Not explicitly stated, but implied to be laboratory-generated samples or well-characterized clinical samples for analytical studies.
-
Cross-Reactivity Studies (Table 2):
- Test Set Sample Size: 346 IgM positive serum specimens (across various microorganisms like Dengue, WNV, JE, Chikungunya, Malaria, Syphilis, etc.).
- Data Provenance: Sourced from patients with confirmed IgM antibodies to potentially cross-reactive microorganisms. Some specific details: Yellow Fever Vaccine recipients from Colombia during a 2016 Zika outbreak; convalescent phase samples for Dengue. Seems retrospective collection.
-
Interfering Substances Study:
- Test Set Sample Size: 3 low reactive human serum samples and 3 normal human serum samples per interfering substance.
- Data Provenance: Laboratory spiked samples.
-
Analytical Sensitivity (LOD) Study:
- Test Set Sample Size: Multiple dilutions of the WHO 1st International Standard for anti-Asian lineage Zika virus antibody (human) were tested in 20 replicates each.
- Data Provenance: WHO International Standard, a reference material.
-
Clinical Studies (Endemic and Non-Endemic Subjects):
- Test Set Sample Size: 807 unique samples were collected from 609 subjects.
- Endemic subjects: 353 samples.
- Non-endemic subjects: 256 samples.
- 744 samples had known Days Post Symptom Onset (PSO).
- Data Provenance: Collected from endemic sites (presumed positive and presumed negative) and non-endemic sites (presumed negative). Some subjects provided serial draws up to 84 days PSO. Some from Zika endemic areas provided paired acute/convalescent draws. This is a prospective collection for the vast majority, as samples were "collected from these subjects." Geographical origin of "endemic" and "non-endemic" sites is not explicitly mentioned by country, but they are clearly differentiated.
- Test Set Sample Size: 807 unique samples were collected from 609 subjects.
-
FDA Performance Panel:
- Test Set Sample Size: Not explicitly stated for the entire panel, but reported for the subsets analyzed: 24 Zika IgM Consensus Positive, 12 Negative, 10 West Nile positive, 10 Dengue positive.
- Data Provenance: Provided by the FDA from individuals infected with Zika, West Nile, or Dengue viruses at various stages of infection. This appears to be a retrospective collection of well-characterized samples.
3. Number of Experts Used to Establish Ground Truth and Qualifications
The text does not specify the number or qualifications of experts used to establish the ground truth for any of the studies.
- Clinical Studies (Endemic and Non-Endemic): The ground truth was established by a "composite reference method that included a validated Zika RT-PCR and CDC Zika MAC-ELISA." While these are laboratory tests, they would have been interpreted by trained laboratory professionals, but no specific expert count or qualification is given.
- FDA Performance Panel: Ground truth ("established consensus of sero-status") was established by the FDA. Again, specific expert details are omitted.
4. Adjudication Method for the Test Set
The text does not explicitly describe an adjudication method (like 2+1, 3+1) for resolving discrepancies in ground truth determination for any of the studies.
- Clinical Studies: The "composite reference method" combining RT-PCR and CDC Zika MAC-ELISA implies a sequential or parallel testing strategy where results from both contribute to the final ground truth. It does not mention an expert adjudication process if these reference methods yielded conflicting results.
- FDA Performance Panel: The "established consensus of sero-status" suggests that a consensus process was used by the FDA, but the details of this process (e.g., how many readers/experts, how discrepancies were resolved) are not provided.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
No, an MRMC comparative effectiveness study involving human readers with and without AI assistance was not done. This device is an ELISA assay, which is a laboratory diagnostic tool, not an AI-assisted diagnostic imaging or interpretation system. Therefore, the concept of human readers improving with AI assistance does not apply here.
6. Standalone (Algorithm Only Without Human-in-the-Loop Performance)
Yes, the performance presented in the "Analytical performance" and "Clinical studies" sections primarily reflects the standalone performance of the ZIKV Detect 2.0 IgM Capture ELISA device. The results (e.g., PPA, NPA, cross-reactivity tables) are direct outputs of the assay based on its internal algorithms and interpretation rules described (Zika ISR, CCA/NCA ratio). While human operators perform the test and interpret the final result based on the device's guidelines, the performance metrics reported are for the device itself against the established ground truth, not for human interpretation aided by the device.
7. Type of Ground Truth Used
- Analytical Sensitivity (LOD): World Health Organization (WHO) 1st International Standard for anti-Asian lineage Zika virus antibody (human) – a standardized reference material.
- Clinical Studies (Endemic and Non-Endemic): A composite reference method consisting of a validated Zika RT-PCR and CDC Zika MAC-ELISA. This is a combination of molecular (RT-PCR) and serological (MAC-ELISA) laboratory tests.
- FDA Performance Panel: "Established consensus of sero-status" – this implies a consensus derived from laboratory tests (Zika IgM, West Nile, Dengue).
8. Sample Size for the Training Set
The document does not explicitly mention a separate "training set" for the device's development in the context of machine learning or AI models. Given that this is an ELISA assay, the concept of a training set as understood in AI/ML is not directly applicable.
However, the "Assay cut-off" section mentions:
- "The study included a testing of eight hundred thirty five (835) specimens that included 72 Zika positive, 198 other flavivirus positive, and 565 other disease positive and negative serum specimens. Receiver Operating Characteristic (ROC) curve analyses were performed to optimize for those cut-off values that maximize both sensitivity and specificity. A rudimentary bootstrap method was applied to minimize bias by any potential outliers in the sample set."
This process of optimizing cut-off values using 835 specimens could be considered analogous to a "training" or "calibration" phase for the device's interpretation algorithm, where the rules for classifying samples (e.g., Zika Ag OD450 > Threshold, Zika ISR > 1.90) were established.
9. How the Ground Truth for the Training Set Was Established
For the 835 specimens used to establish the assay cut-off:
- Ground Truth Establishment: The specimens were categorized as "Zika positive," "other flavivirus positive," and "other disease positive and negative." The method by which these 835 specimens were initially classified (i.e., their ground truth) is not explicitly detailed in the document. It is implied these were diagnostically confirmed samples (e.g., using reference assays like those used in the clinical studies), but the specific process is not described.
§ 866.3935 Zika virus serological reagents.
(a)
Identification. Zika virus serological reagents arein vitro diagnostic devices that consist of antigens or antibodies for the detection of Zika virus or Zika antibodies in human specimens from individuals who have signs and symptoms consistent with Zika virus infection and/or epidemiological risk factors. The detection aids in the diagnosis of current or recent Zika virus infection or serological status. Negative results obtained with this test do not preclude the possibility of Zika virus infection, past or present. Positive results should be interpreted with consideration of other clinical information and laboratory findings and should not be used as the sole basis for treatment or other patient management decisions.(b)
Classification. Class II (special controls). The special controls for this device are:(1) The labeling required under § 809.10(b) of this chapter must include:
(i) An intended use with a detailed description of what the device detects (Zika IgM antibodies, other Zika antibodies, or Zika antigens), the type of results provided to the user, the specimen type for which testing is indicated (
e.g., serum, whole blood), the clinical indications appropriate for test use, and the specific population(s) for which the test is intended.(ii) Performance characteristics from analytical and clinical studies required under paragraphs (b)(2)(ii) and (iii) of this section.
(iii) A detailed explanation of the interpretation of results and criteria for validity of results (
e.g., criteria that internal or external quality controls must meet in order for a test/test run to be valid, minimum signal strength that the sample has to yield to be interpretable as a valid result).(iv) Limiting statements indicating that:
(A) Results are not intended to be used as the sole basis for diagnosis, treatment, or other patient management decisions. The test results should be interpreted in conjunction with clinical observations, patient history, epidemiological information, and other laboratory evidence.
(B) Device results are intended to be followed up according to the latest professional guidelines (
e.g., recommendations from the Centers for Disease Control and Prevention) for the diagnosis of Zika virus infection.(C) Negative test results do not preclude the possibility of Zika virus infection, past or present.
(D) Specimens can result in false negative results on the device if collected outside of the appropriate response window for specific Zika virus antigens or antibodies, as determined by scientific evidence (
e.g., for IgM