(62 days)
The Roche Diagnostics Corporation OnTrak TesTstik™ for PCP is an in vitro diagnostic test intended for professional use for the qualitative detection of PCP in urine at or above a cutoff concentration of 25 ng/mL
OnTrak TesTstik provides only a preliminary analytical test result. A more specific alternate chemical method must be used in order to obtain a confirmed analytical result.
The OnTrak TesTstik PCP assay contained in this submission is an in vitro diagnostic test intended for professional use in the qualitative detection of PCP in urine at or above a cutoff concentration of 25 ng/mL.
The TesTstik assays are based on the principle of microparticle capture inhibition. The test relies on the competition between drug, which may be present in the urine being tested, and drug conjugate immobilized on a membrane.
When the TesTstik is immersed in the urine sample, some of the sample is absorbed into the TesTstik sample pad. The absorbed sample travels through a reagent strip contained in the device by capillary action. In the reagent strip, the sample rehydrates and mobilizes antibody-coated blue The microparticle-urine suspension continues to migrate microparticles. through the reagent strip and comes in contact with the immobilized drug In the absence of drug in the urine, the antibody-coated coniugate. microparticles bind to the drug conjugate and a blue band is formed at the result window ("negative" sign).
When drug is present in the specimen, it binds to the antibody-coated microparticles. If sufficient drug is present, the micro-particles are inhibited from binding the drug conjugate and no blue band is formed at the result window. A positive sample caused the membrane to remain white ("positive" sign).
An additional antibody/antigen reaction occurs at the "TEST VALID" area. The "TEST VALID" blue band forms when antibodies, which are imbedded in the reagent membrane, bind to the antigen on the blue microparticles. The presence of the "TEST VALID" band indicates that the test has completed, the reagents are viable, and the results are ready to interpret.
Here's an analysis of the provided text regarding the acceptance criteria and the study that proves the device meets those criteria:
1. Table of Acceptance Criteria and Reported Device Performance
| Acceptance Criteria Item (Implicit) | Reported Device Performance |
|---|---|
| PCP Cutoff Concentration (for detection) | 25 ng/mL (same as predicate) |
| Precision (at 150% cutoff) | >95% confidence |
| Accuracy (Positive Samples) | 100% positive for PCP (50 samples tested) |
| Accuracy (Negative Samples) | 100% negative for PCP (106 samples tested) |
| Agreement with Comparative Assay (Abuscreen) | 100% agreement between the two assays (OnTrak TesTstik and Abuscreen OnLine for PCP) |
2. Sample Size Used for the Test Set and Data Provenance
- Positive Test Set: 50 samples
- Negative Test Set: 106 samples
- Data Provenance: The text states, "One hundred six (106) urine samples, obtained from a clinical laboratory". This indicates the data is retrospective clinical samples. The country of origin is not explicitly stated.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts
The study does not use human experts to establish ground truth in the traditional sense of medical image interpretation or clinical diagnosis. Instead, the ground truth for the test set was established by analytical methods:
- Experts: Not applicable in the context of interpretation.
- Ground Truth Establishment: Samples were "screened by an automated immunoassay and confirmed positive by GC/MS at the 25 ng/mL cutoff." For negative samples, they were "screened negative by an automated immunoassay relative to a 25 ng/mL cutoff for PCP." This indicates a laboratory-based, objective method for establishing ground truth, not reliant on human expert interpretation of the test device itself.
4. Adjudication Method for the Test Set
Not applicable. The ground truth was established by laboratory instrumentation (GC/MS and automated immunoassay), not by human interpretation requiring adjudication.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done
No. This is an in vitro diagnostic device for analyte detection. MRMC studies are typically performed for devices that involve human interpretation of medical images or diagnostic outputs, assessing the impact of AI on reader performance.
6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done
Yes, this study is a standalone performance assessment. The OnTrak TesTstik for PCP is a qualitative diagnostic test that provides a result (positive/negative) based on a chemical reaction. Its performance is evaluated intrinsically against confirmed samples, not as part of a human-in-the-loop system. The text specifies "professional use," implying a human will perform the test and interpret the visual result, but the "performance" described is the device's ability to accurately detect PCP in the samples.
7. The Type of Ground Truth Used
The ground truth used was analytical confirmation by Gas Chromatography/Mass Spectrometry (GC/MS) for positive samples, and automated immunoassay for negative samples, both relative to a 25 ng/mL cutoff. This is a highly objective and quantitative method for determining the presence or absence of a substance.
8. The Sample Size for the Training Set
The provided text does not mention a training set or any machine learning/AI component. This device is a chemical immunoassay, not an AI-powered diagnostic. Therefore, the concept of a "training set" as it relates to AI models is not applicable here. The device's design and manufacturing likely involved internal development and validation, but not in the context of training a predictive algorithm.
9. How the Ground Truth for the Training Set Was Established
Not applicable, as there is no training set for this type of immunoassay device.
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