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The Omega Laboratories Hair Drug Screening Assay for Carboxy-THC (THCA) is an in vitro diagnostic that is intended to be used for the determination of the presence of cannabinoids in human head and body hair samples. The Omega Laboratories Hair Drug Screening Assay for Carboxy-THC utilizes the International Diagnostic Systems Corp. enzyme linked immunosorbant assay (ELISA) for THC Metabolite Testing Kit, for the qualitative detection of THCA at or above 1 pg/mg of hair for the purpose of identifying the use of cannabinoids.

The Omega Laboratories Hair Drug Screening Assay for Carboxy-THC provides only preliminary analytical test results and must be used in combination with a more specific alternate chemical method in order to obtain a confirmed result. Gas Chromatograph - Mass Spectrometry operating in the selected ion monitoring (SIM) mode or GC/MS/MS in selected reaction mode (SRM) is used as the confirmation method, along with deuterated internal standards.

Omega plans to perform this test at one site. Omega has not performed an evaluation of reproducibility at different laboratories.

Device Description

The test consists of two parts; a pre-analytical proprietary and patent pending hair treatment procedure (to remove THCA from the solid hair matrix to a measurable liquid matrix), and the screening assay. The screening assay is an Enzyme-Linked ImmunoSorbent Assay (ELISA).

Sample is added to a well of the micro strip plate and enzyme conjugate is added, followed by incubation. During this phase, the enzyme-labeled drug conjugate competes with drug in the sample for a limited number of binding sites on the rabbit antibody-coated micro wells. The two bind in proportion to their concentrations. A wash solution is applied to remove any unbound materials. Enzyme substrate solution containing a chromagen is added. The reaction is stopped with an acid and the absorbance is read using a plate reader at 450 nm. A background reading is also taken at 630 nm. Color intensity is inversely proportional to the amount of drug present in the sample.

AI/ML Overview

The Omega Laboratories Hair Drug Screening Assay for THCA (subject device) is an in vitro diagnostic test for the qualitative detection of THCA in human head and body hair samples at or above 1 pg/mg. The device's performance was evaluated through precision and cross-reactivity studies.

1. Table of Acceptance Criteria and Reported Device Performance:

The document does not explicitly state formal "acceptance criteria" against which the device's performance is measured in a pass/fail manner. Instead, the studies demonstrate the device's precision and cross-reactivity, which are implicitly accepted as sufficient for a screening assay that requires confirmation by a more specific method.

Performance Metric	Acceptance Criteria (Implied)	Reported Device Performance
Intra-assay Precision (Qualitative)	All samples at or above cutoff (1.25, 1.50, 1.75, 2.00 pg/mg) should be positive. All samples below cutoff (0, 0.25, 0.50, 0.75 pg/mg) should be negative.	For concentrations 0, 0.25, 0.50, 0.75 pg/mg, all 10 replicates were negative. For concentrations 1.25, 1.50, 1.75, 2.00 pg/mg, all 10 replicates were positive.
Inter-assay Precision (Qualitative)	All samples at or above cutoff (1.25, 1.50, 1.75, 2.00 pg/mg) should be positive. All samples below cutoff (0, 0.25, 0.50, 0.75 pg/mg) should be negative.	For concentrations 0, 0.25, 0.50, 0.75 pg/mg, all 200 replicates were negative. For concentrations 1.25, 1.50, 1.75, 2.00 pg/mg, all 200 replicates were positive.
Cross-reactivity	Acknowledge that structurally similar compounds may contribute to a presumptive positive, but emphasize that these will not confirm via GC/MS/MS. Demonstrate minimal or negligible cross-reactivity with unrelated compounds.	Structurally similar compounds (e.g., (-)-11-nor-9-Carboxy-delta9-THC, (+/-)-11-nor-9-Carboxy-delta9-THC, (-)-11-nor-9-Carboxy-delta8-THC, (-)-delta8-THC, (-)-delta9-THC, (+/-) 11-Hydroxy-delta9-THC, Cannabinol, Cannabidiol) showed varying degrees of cross-reactivity. Nabilone and JWH-018 showed negligible cross-reactivity. The report indicates that GC/MS/MS confirmation resolves these presumptive positives.

2. Sample Sizes Used for the Test Set and Data Provenance:

Intra-assay Precision: 10 replicates for each of 8 different THCA concentrations (80 samples total).
Inter-assay Precision: 200 replicates for each of 8 different THCA concentrations (1600 samples total).
Cross-reactivity: The number of replicates for each compound is listed as 'n=3' for the cutoff control equivalence.
Stability Studies: Two storage time points (1 year and 2.5 years) were used for stability studies, but the number of unique samples tested is not explicitly stated.
Cosmetic Treatment Study: The mean effect was calculated from 8 positive samples with available data for quantitative values before and after all treatments.
Data Provenance: The document does not explicitly state the country of origin of the data or whether the studies were retrospective or prospective. The precision studies used "negative hair samples spiked" to various concentrations, indicating laboratory-controlled conditions rather than direct donor specimens for these specific tests. However, it mentions "Results obtained from donor specimens showed that the qualitative results from the new assays are substantially equivalent to those obtained from the predicate devices," implying some testing with actual donor samples, though details are scarce.

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

The document does not mention the use of experts to establish ground truth for the test set in the context of clinical interpretation or diagnostic decision-making. The ground truth for the precision studies was established by spiking known concentrations of THCA into negative hair samples. For presumptive positive screening results, the document clearly states that Gas Chromatograph-Mass Spectrometry (GC/MS/MS) is used as the confirmation method to obtain a confirmed result, implying this highly precise analytical method serves as the ultimate ground truth for chemical identification and quantification.

4. Adjudication Method for the Test Set:

Not applicable in the conventional sense for clinical studies involving multiple readers. The evaluation of the device relied on analytical performance characteristics (precision, cross-reactivity) where the "ground truth" was determined by the known concentrations of spiked samples or by a reference analytical method (GC/MS/MS) for confirmation.

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. The document describes an in vitro diagnostic device and its analytical performance, not a system involving human readers interpreting results in a clinical setting that would benefit from an MRMC study.

6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done:

Yes, the performance studies described (Precision, Cross-reactivity, Calibrator and Control, Stability, Cosmetic Treatment) are all "standalone" in nature, evaluating the analytical performance of the Omega Laboratories Hair Drug Screening Assay for THCA as an algorithm/assay without human intervention in the detection and initial qualitative determination steps. The human element is involved in the overall workflow (e.g., sample preparation, running the ELISA, interpreting the absorbance readings against a cutoff, and performing GC/MS/MS confirmation), but the reported performance metrics focus on the assay's biochemical and analytical accuracy.

7. The Type of Ground Truth Used:

Precision Studies: Known, spiked concentrations of THCA in negative hair samples served as the ground truth.
Cross-reactivity Studies: Known concentrations of various compounds and their measured cross-reactivity against the target analyte.
Confirmation of Presumptive Positives: Gas Chromatograph-Mass Spectrometry (GC/MS/MS) is explicitly stated as the confirmation method, which serves as the definitive ground truth for chemical identification and quantification of THCA.

8. The Sample Size for the Training Set:

The document does not specify a separate "training set" as it is describing an ELISA assay, not a machine learning algorithm that typically requires a distinct training phase. The analytical methods (ELISA protocol, cutoff determination) are established through development and validation, rather than typical machine learning training.

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

Not applicable for this type of in vitro diagnostic device. The "ground truth" for establishing the assay's parameters (e.g., cutoff, reagent concentrations) would have been determined through internal development and validation processes, likely using characterized samples with known THCA concentrations and optimizing the assay for sensitivity and specificity around the 1 pg/mg cutoff. However, the document does not detail this developmental phase; it focuses on the validation of the final device.

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