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The Psychemedics Microplate EIA for Methamphetamine is an enzyme immunoassay (EIA) for the preliminary qualitative detection of methamphetamine in human head and body hair samples using a methamphetamine calibrator at 5 ng /10 mg hair cutoff for the purpose of identifying methamphetamine use. This product is intended exclusively for inhouse professional use only and is not for sale to anyone.

The Psychemedics Microplate EIA for Methamphetamine in Hair provides only a preliminary analytical test result. To confirm a presumptive screen positive result, a more specific alternate chemical method such as LC/MS/MS (liquid chromatography/mass spectrometry/mass spectrometry) must be used. Clinical consideration and professional judgment must be applied to the interpretation of any drug-of-abuse test result.

Device Description

The test consists of two parts: a pre-analytical hair treatment procedure (to convert the solid matrix of hair to a measurable liquid matrix) and the screening assay, the Psychemedics Microplate EIA for Methamphetamine. The drug is recovered from the hair using a patented method (U.S. Patent #8,084,215).The screening portion of the test system consists of (1) microplate wells coated with multiple drugs including methamphetamine conjugated to bovine serum albumin (BSA) (patent pending), polyclonal sheep anti-methamphetamine, rabbit anti-goat secondary antibody conjugated to HRP (horseradish peroxidase), substrate [3, 3', 5, 5' tetramethylbenzidine (TMB)], HCI to acidify the final reaction, and wash buffer for washing the plates. Absorbance in the wells is read with a microplate reader.

AI/ML Overview

The provided document describes the Psychemedics Microplate EIA for Methamphetamine in Hair, an enzyme immunoassay (EIA) for the preliminary qualitative detection of methamphetamine in human hair samples. The study aims to demonstrate substantial equivalence to a predicate device (Psychemedics Methamphetamine and MDMA Assay, K011185) and alignment with LC/MS/MS results.

Here's the breakdown of the acceptance criteria and study information:

1. Table of Acceptance Criteria and Reported Device Performance

The document doesn't explicitly state "acceptance criteria" in a formal table format. However, it presents performance data that implies the criteria for the device to be considered substantially equivalent and perform adequately. Based on the provided "Agreement Testing" section, we can infer the following:

Acceptance Criteria Category	Specific Criteria (Inferred)	Reported Device Performance
Agreement with Predicate	Low discordance with the predicate device. A high percentage of agreement for both negative and positive results compared to the predicate.	* Discordance between EIA and RIA (predicate) was < 0.2%. * Compared to Predicate (536 samples): * EIA Positive vs. Predicate Positive: 103 * EIA Negative vs. Predicate Negative: 428 * EIA Negative vs. Predicate Positive: 5 (These are "false negatives" by EIA compared to predicate) * EIA Positive vs. Predicate Negative: 0 (These are "false positives" by EIA compared to predicate)
Accuracy (vs. LC/MS/MS)	High agreement with LC/MS/MS confirmation, especially for positive and negative samples, and correct classification of samples around the cutoff. Negative EIA results should be confirmed as truly negative by LC/MS/MS.	* Compared to LC/MS/MS (213 samples): * EIA Positive, LC/MS/MS ≥ Cutoff: 78 (True Positives, clearly above cutoff) * EIA Positive, LC/MS/MS < Cutoff (but ≥ -50% of Cutoff): 9 (May be true positives close to cutoff, or minor discordance) * EIA Positive, LC/MS/MS ≥ Cutoff, and < +50% of Cutoff: 8 (True Positives close to cutoff) * EIA Positive, LC/MS/MS ≥ +50% of Cutoff & < +100% of Cutoff: 8 (True Positives, above cutoff) * EIA Negative, LC/MS/MS 0: 105 (True Negatives) * EIA Negative, LC/MS/MS ≥ -50% of Cutoff & < Cutoff: 3 (False Negatives by EIA, close to cutoff) * EIA Negative, LC/MS/MS ≥ Cutoff, and < +50% of Cutoff: 0 (No false negatives by EIA in this range) * EIA Negative, LC/MS/MS ≥ +50% of Cutoff & < +100% of Cutoff: 2 (False Negatives by EIA) * Crucially, the document states: "The samples [where EIA was negative but predicate was positive] were negative by LC/MS/MS, demonstrating that the EIA negative results, although discordant with the predicate, are correct." This implies the device passed this specific criterion where it disagreed with the predicate.
Precision	Consistent and accurate classification of samples across different concentrations relative to the cutoff (negative, on-cutoff, positive).	* Intra-Assay (e.g., repeatability): * At negative concentrations (B₀ -100% to -25%): 15/15 classified as negative. * At positive concentrations (plus 25% to plus 100%): 15/15 classified as positive. * Inter-Assay (e.g., reproducibility): * At negative concentrations (B₀ -100% to -25%): 75/75 classified as negative. * At positive concentrations (plus 25% to plus 100%): 75/75 classified as positive.
Cosmetic Treatment Impact	Cosmetic treatments should not significantly alter the test result for negative samples (they should remain negative) or change positive samples to negative.	* Negative Samples: 20 samples each treated with bleach, permanent wave, dye, relaxer, and shampoo. "No significant differences were observed for the negative hair samples before and after the treatments; all samples remained negative after the treatments." * Positive Samples: 12 samples each treated with bleach, permanent wave, dye, relaxer, and shampoo. "No positive samples became negative after cosmetic treatment." (Means and ranges of B/B₀ x 100 values were provided, showing consistent positive results).
Environmental Contamination	The wash procedure should effectively remove external contamination such that contaminated samples, after washing, are below the cutoff or correctly identified as contaminated.	* Soaked in 1000 ng/mL Methamphetamine (water): Pre-wash ranged 38.6-98.7 ng/10 mg. Post-wash ranged 1.1-3.0 ng/10 mg. "no samples at or above the cutoff even before application of the wash criterion." * Soaked in 1000 ng/mL Methamphetamine (saline): Pre-wash ranged 8.5-29.3 ng/10 mg. Post-wash ranged 0.2-1.0 ng/10 mg. "all samples negative (i.e, below the cutoff) even without application of the wash criterion." * The "Wash Criterion" calculation and application method for confirmation is described to differentiate ingestion from contamination.
Cross-Reactivity	Limited cross-reactivity with structurally similar compounds. Cross-reactivity with critical compounds should be known and within acceptable limits.	* 5 compounds showed cross-reactivity (MDMA (100%), MDEA (50%), L-methamphetamine (17%), PMA (6.2%), PMMA (83.3%)). * 67 other compounds showed no cross-reactivity.
Interference	No significant interference from common substances within specified concentration ranges.	* 128 compounds tested for interference at +/-50% of the cutoff showed no interference.
Recovery	Recovery of methamphetamine from hair of users should be comparable to the predicate device.	* "Recovery of methamphetamine from hair of methamphetamine users was shown to be substantially equivalent to that of the predicate device."
Stability	Calibrator and control solutions should remain stable for a defined period.	* "Stability of methamphetamine in methanol in the presence of other drugs of abuse was shown to exceed 1 year."

2. Sample Size Used for the Test Set and Data Provenance

Agreement Testing (vs. Predicate): 536 hair samples.
- 16% (approximately 86 samples) were body hair samples; the remainder were head hair.
- Data provenance is not explicitly stated (e.g., country of origin, retrospective/prospective). However, it's implied to be real-world human hair samples.
Agreement Testing (vs. LC/MS/MS): 213 of the 536 samples.
Precision Studies:
- Intra-Assay: 15 replicates per level (negative: 4 levels, positive: 4 levels). Total 120 tests.
- Inter-Assay: 75 replicates per level (negative: 4 levels, positive: 4 levels). Total 600 tests.
Cosmetic Treatment Study:
- 20 methamphetamine-negative samples per cosmetic treatment type (5 types = 100 samples).
- 12 methamphetamine-positive samples per cosmetic treatment type (5 types = 60 samples).
Contamination Study: The number of hair samples used for the contamination study is not explicitly stated, but it describes soaking hair in methamphetamine solutions and then washing them.
Cross-reactivity and Interference Studies:
- Cross-reactivity: 5 compounds that cross-reacted, plus 67 other compounds showing no cross-reactivity (total 72 compounds).
- Interference: 128 compounds tested.

The data provenance (country of origin, retrospective/prospective) is not explicitly stated in the provided text for any of the studies.

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

The ground truth in this submission is established through:
- Predicate Device (RIA): The Psychemedics Methamphetamine and MDMA Assay, K011185. This is another diagnostic test, itself validated.
- LC/MS/MS (Liquid Chromatography/Mass Spectrometry/Mass Spectrometry): This is described as a "more specific alternate chemical method" and is used for confirmation. This technique is typically considered the gold standard for drug quantification.
- Clinical consideration and professional judgment: The document notes that these "must be applied to the interpretation of any drug-of-abuse test result."
No "experts" in the traditional sense of human readers/interpreters (e.g., radiologists) were used to establish ground truth. The ground truth is based on the analytical results of the predicate device and, more definitively, the LC/MS/MS method. The qualifications of individuals performing these LC/MS/MS confirmations are not detailed, but it's a standard laboratory practice requiring trained analytical chemists.

4. Adjudication Method for the Test Set

Since the ground truth is established by objective analytical methods (predicate device, and primarily LC/MS/MS), there is no adjudication method by multiple human experts (e.g., 2+1, 3+1). The LC/MS/MS results serve as the definitive ground truth for the subsets of samples that underwent that testing.

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

There was no MRMC comparative effectiveness study performed. This device is an immunoassay, and its output is an analytical result (positive/negative based on a cutoff, or quantitative for confirmation) rather than an image or complex data requiring interpretation by multiple human readers. Therefore, the concept of "human readers improving with AI vs. without AI assistance" does not apply here.

6. Standalone (Algorithm Only) Performance

Yes, the studies reported are for the standalone performance of the Psychemedics Microplate EIA for Methamphetamine in Hair. The performance metrics (precision, agreement with predicate/LC/MS/MS, cosmetic treatment, contamination, cross-reactivity, interference, recovery, stability) all describe the direct output of the assay itself, without human-in-the-loop assistance in the interpretation of the primary result (detection of methamphetamine).

7. Type of Ground Truth Used

The primary ground truth used is LC/MS/MS (Liquid Chromatography/Mass Spectrometry/Mass Spectrometry), which is a gold-standard analytical confirmation method for drug testing. The predicate device (RIA) also served as a comparative ground truth to demonstrate substantial equivalence, but LC/MS/MS was utilized to confirm the accuracy of discordant results.

8. Sample Size for the Training Set

The document does not provide information on the sample size used for a training set. This is an immunoassay, which typically involves pre-developed reagents and protocols rather than a machine learning algorithm requiring a "training set" for model development. The precision and agreement studies are performance validation tests, not training data.

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

As there is no mention of a "training set" in the context of a machine learning algorithm, this question is not applicable based on the provided text. The device is a chemical assay, not an AI/ML diagnostic.

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