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The Quest Diagnostics HairCheck-DT (Cocaine) test system utilizes an Enzyme Linked Immunosorbent Assay (ELISA) for the qualitative detection of cocaine in head hair samples through the measurement of cocaine and cocaine metabolites for concentrations at or above 300 pg/mg hair. This test system has not been evaluated for use with hair specimens from locations other than the head. It is an in vitro diagnostic device intended exclusively for in-house professional use and is not intended for sale to anyone.

The HairCheck-DT (Cocaine) test system was evaluated in two distinct study populations; individuals known to be chronic drug abusers, and individuals proclaiming to be drug-free.

The Quest Diagnostics HairCheck-DT (Cocaine) test system provides only a preliminary analytical test result. To confirm a presumptive screen positive result, a more specific alternate chemical method, such as gas chromatography-mass spectrometry (GC-MS) or Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS), must be used. Clinical consideration and professional judgment should be applied to any drug of abuse test result, particularly when preliminary positive results are obtained.

The Quest Diagnostics Hair Check-DT (Cocaine) test system utilizes an Enzyme Linked Immunosorbent Assay (ELISA) for the qualitative detection of cocaine in head hair samples through the measurement of cocaine and cocaine metabolites for concentrations at or above 300 pg/mg hair. This test system has not been evaluated for use with hair specimens from locations other than the head. It is an in vitro diagnostic device intended exclusively for in-house professional use and is not intended for sale to anyone.
The ELISA Cocaine Kit is based on the competition for a limited number of antibody sites by unlabeled cocaine/cocaine metabolites and enzyme-labeled drug. The two will bind to the antibody in proportion to their concentration in solution.
Once accessioned in the lab, the aluminum foil is opened and the specimen is cut at approxima 3.9 cm from the root end. This specimen is cut into smaller lengths and mixed to ens homogeneity. Ten milligrams of the specimen is weighed out and placed into a properly labeled test tube. The specimen is then washed with methanol, decanted, and then placed in hot methanol containing 0.5% (v/v) trifluoroacetic acid for one hour forty-five minutes. The extracted methanol solution is then transferred to a new tube and evaporated under nitrogen. The tubes are reconstituted with phosphate buffer and assayed using the Cocaine ELISA Kit. This kit is a solid-phase microtiter plate immunoassay in which the microwells are coated with a high affinity capture antibody to cocaine. A hair sample extract is added to the well, followed by the horseradish peroxidase (HRP) enzyme conjugate. During this initial phase, the enzyme conjugate competes with the analyte in the sample for binding sites on the antibody-coated microwells. A wash solution (Tween-20 in phosphate buffered saline solution) is then applied to remove any unbound materials such as excess conjugate and residual sample. Enzyme substrate solution containing 3, 3', 5, 5'-tetramethylbenzidine (TMB) is then added for the final color development process. The reaction is stopped with 1N sulfuric acid and the absorbance is read at 450 nm, with a reference wavelength of 620 nm, using a plate reader. Color intensity is inversely proportional to the amount of analyte present in the sample. Therefore, samples that contain drug or analyte will inhibit binding of the enzyme conjugate to the antibody, resulting in little substrate binding and less color development than in the negative calibrator. For the screening assay an absorbance less than or equal to the absorbance of the 300 pg cocaine/mg hair cutoff calibrator is indicative of the presence of cocaine/cocaine metabolites.

The Quest Diagnostics HairCheck-DT (Cocaine) test system is an in vitro diagnostic device that uses an Enzyme Linked Immunosorbent Assay (ELISA) for the qualitative detection of cocaine and cocaine metabolites in head hair samples at concentrations at or above 300 pg/mg hair. A positive result from this screening test requires confirmation using a more specific alternate chemical method, such as gas chromatography-mass spectrometry (GC/MS) or Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS).

Here's an analysis of the acceptance criteria and the study that proves the device meets them:

1. Table of Acceptance Criteria and Reported Device Performance

2. Sample Size and Data Provenance for Test Set

• Precision/Reproducibility: 9 samples/levels tested in quintuplicate (5 replicates) over 10 days, resulting in 50 measurements per level (9 levels: 0%, 25%, 50%, 75%, 100%, 125%, 150%, 175%, 200% of cutoff). Total of 450 measurements for precision. Data provenance is implied to be laboratory-prepared spiked samples, origin not specified.
• Cross-Reactivity:
  • Structurally Related Compounds: 11 compounds tested. Serial dilutions were used to determine the concentration producing an OD akin to the cutoff. Specific number of test samples per compound not detailed, but implies multiple tests per compound across dilutions.
  • Interference (Unrelated Compounds): 143 compounds tested. Each spiked into low control (150 pg/mg) and high control (450 pg/mg) negative hair matrix. 10 hair dyeing compounds evaluated starting at 500 µg/mL. This suggests at least 2 tests per compound (low control spike + high control spike).
• Method Comparison: 100 donor specimens (50 negative, 50 positive, with specific ranges near cutoff). Data provenance indicates these were "routine donor hair specimens provided by the Quest Diagnostics testing laboratory," previously confirmed by GC-MS, and eligible for discard. This implies retrospective clinical data from unspecified geographic origins.
• Within-Run Specimen Extraction Reproducibility: 5 cocaine positive specimens, each tested in 3 replicates.
• Specimen Shipping Stability: 56 hair samples (28 confirmed positive, including 3 near cutoff; 28 confirmed negative, including 3 near cutoff). These were shipped to 8 different geographical locations. This represents a prospective study with controlled shipping conditions.
• Cosmetic Hair Treatment Studies: 120 hair samples (60 confirmed positive by GC-MS, 60 screened negative by ELISA). These were subjected to 5 different cosmetic hair treatments or left untreated. Specific breakdown by treatment group is 12 positive and 12 negative samples per treatment type (shampoo, brown dye, bleach, perm, relaxer, and untreated controls implicitly for the ELISA results where %change is noted relative to pre-treatment of the same sample).

3. Number of Experts and Qualifications for Ground Truth

The document does not explicitly state the number of experts or their qualifications for establishing ground truth. However, for the Method Comparison study and other stability/reproducibility studies comparing results against a definitive method, the ground truth relies on confirmation by GC-MS (Gas Chromatography-Mass Spectrometry). This is a highly sensitive and specific analytical technique commonly used as a gold standard in toxicology. The interpretation and operation of GC-MS would typically be performed by highly trained analytical chemists or toxicologists in a certified laboratory setting, but specific expert qualifications are not provided.

For the cosmetic hair treatment study, "Cocaine positive hair is defined as a hair sample confirmed by GC-MS as having greater than 300 pg/mg cocaine." This again points to GC-MS as the ground truth.

4. Adjudication Method for Test Set

The document does not describe an adjudication method involving human experts for the test set. Instead, the device's performance is compared directly against the results obtained from a reference method, specifically GC-MS. Discrepancies (e.g., in the Method Comparison study) are analyzed and explained by the submitting company, not adjudicated by a panel of independent experts in the typical clinical sense. For example, specific discrepancies are attributed to pink hair dye interference or samples being near the cutoff.

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study

No multi-reader multi-case (MRMC) comparative effectiveness study was mentioned. This device is an in vitro diagnostic (ELISA), not an imaging or assistive technology that human readers would use. Therefore, the concept of "how much human readers improve with AI vs without AI assistance" does not apply.

6. Standalone Performance Study

Yes, a standalone performance study was done. The entire document describes the performance of the algorithm/device only (the HairCheck-DT (Cocaine) ELISA test system) without human-in-the-loop performance modifications beyond the standard operational procedures for running an ELISA and interpreting its results against a cutoff. The device provides "only a preliminary analytical test result," and "to confirm a presumptive screen positive result, a more specific alternate chemical method, such as gas chromatography-mass spectrometry (GC/MS) must be used." This clearly indicates its standalone screening role.

7. Type of Ground Truth Used

The primary ground truth used for evaluating the device's performance is quantitative Gas Chromatography-Mass Spectrometry (GC-MS) analysis. This is considered a highly reliable and definitive analytical method in toxicology for confirming the presence and concentration of substances. In some cases, outcomes data or specifically defined reference material concentrations act as the ground truth (e.g., for precision, cross-reactivity with spiked samples).

8. Sample Size for the Training Set

The document provided does not mention a "training set" or "training data" in the context of machine learning, as this device is a chemical immunoassay (ELISA), not an AI/ML algorithm that requires training data in that sense. The studies described are performance validation studies for the immunoassay.

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

As noted in point 8, there is no "training set" in the machine learning sense. For the development and establishment of the immunoassay, the "ground truth" for calibrators and controls would be established by preparing solutions of known concentrations of cocaine and its metabolites using certified reference materials, and comparing against a reference method like GC-MS during the assay's development. The document mentions that "40X Calibrator and Control solutions are prepared from Cerilliant C-008, 1.0 mg/mL Cocaine in Acetonitrile Certified Reference Material." This demonstrates the rigorous process of establishing known concentrations for quality control and calibration purposes.

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