(90 days)
The TECHLAB® E. HISTOLYTICA QUIK CHEK™ test is a rapid membrane enzyme immunoassay for the qualitative detection of adhesin from Entamoeba histolytica in a single use cassette. It is intended for use with human fecal specimens from patients with diarrhea or dysentery as an aid in the diagnosis of E. histolytica gastrointestinal infection. Test results should be considered in conjunction with patient history. FOR IN VITRO DIAGNOSTIC USE
The E. HISTOLYTICA QUIK CHEK™ test uses antibodies to adhesin. The device contains a Reaction Window with two vertical lines of immobilized antibodies. The test line ("T") contains monoclonal antibodies specific for E. histolytica adhesin. The control line ("C") contains antibodies to horseradish peroxidase (HRP). The Conjugate consists of polyclonal antibodies to E. histolytica adhesin coupled to horseradish peroxidase. To perform the test, the sample is added to a tube containing a mixture of Diluent and Conjugate. The diluted sample-conjugate mixture is added to the Sample Well and the device is allowed to incubate at room temperature for 15 minutes. During the incubation, E. histolytica adhesin in the samples bind to the antibodyperoxidase conjugate. The antigen-antibody complexes migrate through a filter pad to a membrane where they are captured by the immobilized antibodies in the Reaction Window is subsequently washed with Wash Buffer, and the test is developed with the addition of Substrate. After a 10 minute incubation period, the "T" reaction is examined visually for the appearance of a vertical blue line on the "T" side of the Reaction Window. A blue line indicates a positive test. A positive "C" reaction, indicated by a vertical blue line on the "C" side of the Reaction Window, monitors/confirms that the sample and reagents were added correctly, the reagents were active at the time of performing the assay, and that the sample migrated properly through the Membrane Device. It also confirms the reactivity of the other reagents associated with the assay.
Here's a breakdown of the acceptance criteria and the study that proves the device meets them, based on the provided text:
E. HISTOLYTICA QUIK CHEK™ Performance Study Summary
The E. HISTOLYTICA QUIK CHEK™ test is a rapid membrane enzyme immunoassay for the qualitative detection of adhesin from Entamoeba histolytica in human fecal specimens.
1. Acceptance Criteria and Reported Device Performance
The study compares the E. HISTOLYTICA QUIK CHEK™ test to a Composite Reference Method (CRM). While explicit "acceptance criteria" are not listed in terms of specific sensitivity/specificity thresholds, the overall performance against the CRM demonstrates the device's efficacy. The reported performance for prospective samples, while showing lower sensitivity, is accompanied by 100% specificity and PPV, indicating no false positives in this dataset. The retrospective data shows 100% sensitivity and specificity.
Table 1: Acceptance Criteria (Implied) and Reported Device Performance
| Metric | Implied Acceptance Goal (vs. CRM) | Reported Performance (Prospective Samples, N=755) | Confidence Limits (95%) | Reported Performance (Retrospective Samples, N=96) | Confidence Limits (95%) |
|---|---|---|---|---|---|
| Sensitivity | High | 40.0% | 7.3% - 83.0% | 100% | 85.9% - 100% |
| Specificity | High | 100% | 99.4% - 100% | 100% | 93.1% - 100% |
| Predictive Positive Value | High | 100% | 19.8% - 100% | N/A (not explicitly shown in table) | N/A |
| Predictive Negative Value | High | 99.6% | 98.7% - 99.9% | N/A (not explicitly shown in table) | N/A |
Note: The three false-negative results in the prospective study were PCR positive but antigen negative, suggesting a limitation in antigen detection for those specific samples, rather than a lack of E. histolytica presence.
2. Sample Size Used for the Test Set and Data Provenance
- Total Sample Size: 851 fecal samples
- Prospective Samples: 755
- Provenance: Not explicitly stated, but collected from "3 independent sites," implying diverse geographical locations likely within the US given the FDA submission. The context suggests these were real-world clinical samples collected over time.
- Retrospective Samples: 96
- Provenance: Not explicitly stated, but referred to as "frozen (retrospective) specimens." Likely from archived clinical samples.
- Prospective Samples: 755
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications
Not explicitly stated. The ground truth (Composite Reference Method) involves a combination of tests, not directly requiring individual expert interpretation per se, beyond the expertise required to perform and interpret the individual tests (Microscopy, FDA cleared multiplex NAAT test, Alternate PCR with sequencing).
4. Adjudication Method for the Test Set
The adjudication method for the ground truth (Composite Reference Method - CRM) is clearly defined by an algorithm:
| Microscopy | FDA cleared multiplex NAAT test | Alternate PCR with sequencing | CRM Result |
|---|---|---|---|
| Pos | Pos | Pos | Pos |
| Pos | Pos | Neg | Neg |
| Pos | Neg | Pos | Pos |
| Pos | Neg | Neg | Neg |
| Neg | Pos | Pos | Pos |
| Neg | Pos | Neg | Neg |
| Neg | Neg | N/A | Neg |
For cases where Microscopy and multiplex NAAT were both negative, no further PCR testing was performed, and the CRM result was deemed negative. This is a rule-based adjudication.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
No, a multi-reader multi-case (MRMC) comparative effectiveness study was not explicitly mentioned as part of this submission. The study focuses on the standalone performance of the device against a Composite Reference Method.
6. Standalone Performance Study
Yes, a standalone performance study was conducted. The E. HISTOLYTICA QUIK CHEK™ test was evaluated as an "algorithm only (without human-in-the-loop performance)" device, as it is an in vitro diagnostic which provides a visual qualitative result that is then interpreted by a user. The performance metrics (sensitivity, specificity, PPV, NPV) presented in Tables 1 and 2 directly reflect this standalone capability, comparing its results directly to the CRM. The "visual" interpretation by a human is part of the intended use, but the analytical performance is solely dependent on the device's output.
7. Type of Ground Truth Used
The primary ground truth used was a Composite Reference Method (CRM). This CRM combined:
- Microscopy
- An FDA cleared multiplex NAAT test
- Alternate PCR with sequencing
This approach aims to establish a more robust and accurate determination of the true E. histolytica infection status than any single method alone.
8. Sample Size for the Training Set
The document does not explicitly state a separate "training set" sample size or a description of model training, as this device is a rapid membrane enzyme immunoassay (a chemical/biological test), not an AI/machine learning algorithm that requires training data in the traditional sense. The document describes analytical and clinical validation, which ensures the device's inherent functional performance.
9. How the Ground Truth for the Training Set Was Established
As noted above, this device is not an AI/ML algorithm requiring a training set in the conventional sense. Therefore, the concept of establishing ground truth for a training set does not apply here. The device's underlying principles are based on antibody-antigen reactions. Its design and development would have involved internal validation and optimization, but not "training" on a dataset in the way an AI model would.
§ 866.3220
Entamoeba histolytica serological reagents.(a)
Identification. Entamoeba histolytica serological reagents are devices that consist of antigens and antisera used in serological tests to identify antibodies toEntamoeba histolytica in serum. Additionally, some of these reagents consist of antisera conjugated with a fluorescent dye (immunofluorescent reagents) used to identifyEntamoeba histolytica directly from clinical specimens. The identification aids in the diagnosis of amebiasis caused by the microscopic protozoan parasiteEntamoeba histolytica and provides epidemiological information on diseases caused by this parasite. The parasite may invade the skin, liver, intestines, lungs, and diaphragm, causing disease conditions such as indolent ulcers, an amebic hepatitis, amebic dysentery, and pulmonary lesions.(b)
Classification. Class II (special controls). The device is exempt from the premarket notification procedures in subpart E of part 807 of this chapter subject to § 866.9.