(217 days)
The Thermo Electron CT OIA assay is an Optical ImmunoAssay (OIA) test for the rapid, qualitative detection of chlamydial antigen from female endocervical swab specimens. This test is intended for in vitro diagnostic use as an aid in identifying the presence of Chlamydia trachomatis antigen. The assay is intended for in vitro diagnostic use with symptomatic females in populations at risk for sexually transmitted diseases.
CT OIA test results are presumptive evidence for either the presence or absence of C. trachomatis. Definitive laboratory evidence for the presence/ absence of C. trachomatis would need additional testing. CT OIA test results should not preclude empiric treatment of women with overt symptoms of PID. Performance for use in asymptomatic male and female populations has not been established.
The CT OIA test involves the qualitative extraction of antigen specific to the Chlamydia genus. The Optical ImmunoAssay technology enables the direct visual detection of a physical change in the optical thickness of molecular thin films. This change is a result of antigen-antibody binding on an optical surface (silicon wafer). When an extracted specimen is placed directly on the optical surface, the immobilized specific antibodies capture the antigen. After washing, the substrate is added, increasing the thickness (mass enhancement) of the molecular thin film. This change in thickness alters the reflected light path and is visually perceived as a color change. Slight changes in optical thickness produce a distinct, visible color change. A positive result appears as a purple spot on the predominant gold background. When antigen is not present in the specimen, no binding takes place. Therefore, the optical thickness remains unchanged and the surface retains the original gold color indicating a negative result.
Here's a breakdown of the acceptance criteria and study information for the Thermo Flectron CT OIA device, based on the provided text:
1. Table of Acceptance Criteria and Reported Device Performance
The document does not explicitly state pre-defined acceptance criteria for clinical performance (e.g., "Sensitivity must be >= X%, Specificity must be >= Y%"). Instead, it reports the observed performance characteristics. Given this, the table will present the key performance metrics as reported in the study:
| Metric | Reported Device Performance (%) |
|---|---|
| Clinical Sensitivity | 73.8 |
| Clinical Specificity | 98.4 |
| Overall PPV | 87.3 |
| Overall NPV | 96.2 |
| Reproducibility | 87.7 |
2. Sample Size Used for the Test Set and Data Provenance
- Sample Size for Clinical Sensitivity and Specificity: 767 symptomatic female patients were included in the final analysis. (Initially, 885 female patients were enrolled, but 118 were excluded).
- Sample Size for Reproducibility: Reproducibility testing was performed on three blinded panels, though the exact number of individual samples within these panels isn't specified (71/81 successful tests are mentioned, suggesting 81 blinded samples).
- Data Provenance: The study was a "multicenter study at four geographically diverse clinical sites" located in the Northwest, Midwest, Mid-Atlantic, and Southeast regions of the United States. It was a prospective study as patients were enrolled and tested.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of those Experts
The document does not specify the number or qualifications of experts involved in establishing the ground truth.
4. Adjudication Method for the Test Set
The document does not explicitly mention an adjudication method. For the clinical sensitivity and specificity study, the CT OIA test was compared to a "commercially available LCx nucleic acid amplification test for C. trachomatis" as the primary reference method. "Secondary confirmation testing of positive OIA was done by a commercially available PCR test." This suggests a two-step approach for ground truth, but not an adjudication process among human readers.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
No, a multi-reader multi-case (MRMC) comparative effectiveness study was not performed. The study focuses on the standalone performance of the device compared to a reference method, not on how human readers' performance improves with or without AI assistance.
6. Standalone (Algorithm only without human-in-the-loop performance) Study
Yes, a standalone study was conducted. The performance metrics (sensitivity, specificity, PPV, NPV) reported are for the CT OIA assay itself, in comparison to a reference method (LCx and PCR), without human interpretation as part of the primary device output. The device itself is an "Optical ImmunoAssay technology [that] enables the direct visual detection of a physical change in the optical thickness... visually perceived as a color change. A positive result appears as a purple spot on the predominant gold background." While a human observes this color change, the reported performance is for the diagnostic test's ability to accurately reflect the presence of the antigen, not for a human's ability to interpret an image provided by an AI.
7. Type of Ground Truth Used
The primary ground truth for the clinical sensitivity and specificity study was a commercially available LCx Nucleic Acid Amplification Test (NAAT) for C. trachomatis. Positive OIA results were also subject to secondary confirmation testing by a commercially available PCR test.
8. Sample Size for the Training Set
The document does not mention a separate "training set" or "training data" in the context of developing the CT OIA assay. This assay is a diagnostic test based on Optical ImmunoAssay technology, likely developed and validated through laboratory experimentation and calibration rather than machine learning on a large dataset. Therefore, the concept of a training set for an algorithm is not applicable here.
9. How the Ground Truth for the Training Set Was Established
As noted above, the concept of a training set as understood in AI/ML is not applicable. The device's development would involve establishing its analytical performance characteristics (e.g., detection limits, cross-reactivity) through laboratory studies using characterized samples, rather than establishing "ground truth" for a training set in a clinical context.
§ 866.3120 Chlamydia serological reagents.
(a)
Identification. Chlamydia serological reagents are devices that consist of antigens and antisera used in serological tests to identify antibodies to chlamydia in serum. Additionally, some of these reagents consist of chlamydia antisera conjugated with a fluorescent dye used to identify chlamydia directly from clinical specimens or cultured isolates derived from clinical specimens. The identification aids in the diagnosis of disease caused by bacteria belonging to the genusChlamydia and provides epidemiological information on these diseases. Chlamydia are the causative agents of psittacosis (a form of pneumonia), lymphogranuloma venereum (a venereal disease), and trachoma (a chronic disease of the eye and eyelid).(b)
Classification. Class I (general controls).