(322 days)
The Psychemedics homogeneous enzyme immunoassay (HEIA) for amphetamines in hair is an enzyme immunoassay system for the preliminary qualitative detection of methamphetamine in human head and body hair using a methamphetamine calibrator at 3 ng methamphetamine/10 mg hair or 5 ng methamphetamine/10 mg hair for the purpose of identifying methamphetamine use, and for the preliminary qualitative detection of amphetamine in human head and body hair using an amphetamine calibrator at 3 ng amphetamine/10 mg hair for the purpose of identifying amphetamine use.
This is an in vitro diagnostic device intended exclusively for Psychemedics use only and is not for sale to anyone. The Psychemedics HEIA for amphetamines in hair provides only a preliminary analytical test result. A more specific alternative chemical method must be used in order to obtain a confirmed analytical result. Liquid Chromatography/Mass Spectrometry/Mass Spectrometry (LC/MS/MS) is the preferred confirmatory method.
The test consists of two parts; a pre-analytical hair treatment procedure (to extract amphetamines from the solid hair matrix to a measurable liquid matrix) and the screening assay, the Psychemedics Amphetamines HEIA. The screening portion of the test system is based on competition for antibody binding sites between drug in the measurable liquid matrix and drug-labeled recombinant glucose-6-phosphate dehydrogenase (G6PDH). As the antibody binds labeled G6PDH, enzyme activity decreases. In the presence of drug, enzyme activity increases in direct proportion to the drug concentration. Active enzyme reduces nicotinamide adenine dinucleotide (NAD) to NADH in the presence of glucose 6-phosphate (G6P), resulting in an absorbance change that is measured spectrophotometrically.
The Psychemedics Amphetamines HEIA consists of reagents R1 (anti-methamphetamine monoclonal antibody with substrate) and R2 (methamphetamine labeled recombinant G6PDH) for the detection of methamphetamine, and reagents R1 (anti-amphetamine monoclonal antibody with substrate) and R2 (amphetamine labeled recombinant G6PDH) for the detection of amphetamine.
The provided document describes the performance of the Psychemedics Homogeneous Enzyme Immunoassay (HEIA) for Amphetamines in Hair. This device is an in vitro diagnostic device intended for preliminary qualitative detection of methamphetamine and amphetamine in human hair.
Here's an analysis of the acceptance criteria and study data:
1. Table of Acceptance Criteria and Reported Device Performance
The document does not explicitly state formal acceptance criteria values (e.g., "sensitivity must be > X%", "specificity must be > Y%"). Instead, it presents precision data and comparison studies against a confirmatory method (LC/MS/MS) to demonstrate acceptable performance. The acceptance is implied by the robust precision and high agreement with the confirmatory method, as well as satisfactory performance with cosmetic treatments and lack of cross-reactivity/interference from other substances.
However, we can infer some criteria from the presented data. The device's performance is summarized in its ability to correctly classify samples as positive or negative compared to LC/MS/MS and its precision at various concentration levels.
Inferred Acceptance Criteria vs. Reported Performance:
| Feature | Acceptance Criteria (Implied) | Reported Device Performance |
|---|---|---|
| Precision (Intra-Assay) | Consistent classification (all negative below cutoff, all positive above cutoff) at various concentration levels (e.g., -100%, -75%, -50%, -25%, +25%, +50%, +75%, +100% relative to cutoff). | Methamphetamine (3 ng/10 mg & 5 ng/10 mg calibrator), Amphetamine (3 ng/10 mg calibrator): |
- At -100%, -75%, -50%, -25% of cutoff: All 8 replicates per level were correctly identified as Negative.
- At +25%, +50%, +75%, +100% of cutoff: All 8 replicates per level were correctly identified as Positive. This indicates perfect intra-assay precision for the tested ranges. |
| Precision (Inter-Assay) | Consistent classification (all negative below cutoff, all positive above cutoff) at various concentration levels (e.g., -100%, -75%, -50%, -25%, +25%, +50%, +75%, +100% relative to cutoff) over multiple runs/days. | Methamphetamine (3 ng/10 mg & 5 ng/10 mg calibrator), Amphetamine (3 ng/10 mg calibrator): - At -100%, -75%, -50%, -25% of cutoff: All 80 replicates per level were correctly identified as Negative.
- At +25%, +50%, +75%, +100% of cutoff: All 80 replicates per level were correctly identified as Positive. This indicates perfect inter-assay precision for the tested ranges. |
| Agreement with LC/MS/MS | High concordance between HEIA results (positive/negative) and LC/MS/MS results across the dynamic range, with minimal false positives or negatives, particularly near the cutoff. Acknowledgment and explanation of expected discordant samples due to washing protocols should be provided. | Methamphetamine (3 ng/10 mg calibrator): - 53 samples negative by HEIA were 4.50 ng/10 mg by LC/MS/MS.
- 5 negative HEIA samples were between 1.5-2.99 ng/10 mg by LC/MS/MS (near cutoff).
-> Overall: High agreement. Discordant results (2 samples) were explained by the washing protocol for LC/MS/MS that is not applied to initial HEIA screening, leading to lower LC/MS/MS values after washing.
Methamphetamine (5 ng/10 mg calibrator): - 45 samples negative by HEIA were 7.50 ng/10 mg by LC/MS/MS.
- 4 negative HEIA samples were between 2.5-4.99 ng/10 mg by LC/MS/MS (near cutoff).
-> Overall: High agreement. Discordant results (2 samples) were explained by the washing protocol.
Amphetamine (3 ng/10 mg calibrator): - 42 samples negative by HEIA were 4.50 ng/10 mg by LC/MS/MS.
- 6 negative HEIA samples were between 1.5-2.99 ng/10 mg by LC/MS/MS (near cutoff).
-> Overall: High agreement. Discordant results (2 samples) were explained by the washing protocol. |
| Cross-Reactivity | Limited significant cross-reactivity with common structurally similar compounds and no cross-reactivity with a wide range of other tested compounds at specified cutoffs. | Methamphetamine Assays (3 ng/10 mg & 5 ng/10 mg calibrators): - MDMA, Para-Methoxy Methamphetamine, 1R, 2S Ephedrine, and MDEA showed some cross-reactivity (81-10% at 3 ng/10 mg; 83-10% at 5 ng/10 mg) requiring higher concentrations to be equivalent to the cutoff.
- R-Methamphetamine showed low cross-reactivity (2%).
- D-Amphetamine, L-Amphetamine, and MDA showed Overall: Cosmetic treatments did not affect the results. |
| Sample Shipping Stability| Samples should remain stable (positive remain positive) after typical storage and shipping conditions for a reasonable period. | - 9 methamphetamine-positive samples remained positive for approximately 8 months after storage and two coast-to-coast shipments. - 9 amphetamine-positive samples remained positive for approximately 6 months after storage and two coast-to-coast shipments.
-> Overall: Demonstrated sufficient stability. |
| Recovery | Sufficient recovery of the target analytes during the extraction procedure. | - Recovery of methamphetamine in the phosphate buffer extraction was approximately 100% complete after 3 hours. - Recovery of amphetamine in the phosphate buffer extraction was approximately 100% complete after 3 hours.
-> Overall: Satisfactory recovery. |
2. Sample Sizes and Data Provenance for the Test Set
The device uses multiple test sets for different aspects of its performance evaluation:
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Precision Studies:
- Methamphetamine (3 ng/10 mg calibrator): 8 replicates per level (intra-assay) and 80 replicates per level (inter-assay) for a total of 8 levels (4 negative, 4 positive).
- Intra-assay: 8 samples/level * 8 levels = 64 samples.
- Inter-assay: 80 samples/level * 8 levels = 640 samples.
- Methamphetamine (5 ng/10 mg calibrator): Same as above (64 intra-assay, 640 inter-assay samples).
- Amphetamine (3 ng/10 mg calibrator): Same as above (64 intra-assay, 640 inter-assay samples).
- Data Provenance: Spiked negative hair samples with LC/MS/MS validated calibrator and control solutions. This suggests controlled laboratory samples. No specific country of origin is mentioned, but "workplace setting" is mentioned for the comparison studies.
- Methamphetamine (3 ng/10 mg calibrator): 8 replicates per level (intra-assay) and 80 replicates per level (inter-assay) for a total of 8 levels (4 negative, 4 positive).
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Comparison Studies (HEIA vs. LC/MS/MS):
- Methamphetamine (3 ng/10 mg calibrator): 114 individual hair samples. 58 negative and 56 positive initially identified by the test device.
- Methamphetamine (5 ng/10 mg calibrator): 94 individual hair samples. 49 negative and 45 positive initially identified by the test device.
- Amphetamine (3 ng/10 mg calibrator): 96 individual hair samples. 48 negative and 48 positive initially identified by the test device.
- Data Provenance: Hair samples collected anonymously from a "workplace setting." These appear to be retrospective real-world samples. The document does not specify a country of origin.
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Cross-Reactivity & Interference Studies: Not specified, but likely involved a series of controlled laboratory experiments using specific concentrations of the compounds.
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Cosmetic Treatment Studies:
- Methamphetamine: 5 methamphetamine-negative head hair samples, 4 methamphetamine-positive head hair samples.
- Amphetamine: 9 amphetamine-negative head hair samples, 4 amphetamine-positive head hair samples.
- Data Provenance: Not explicitly stated but likely controlled laboratory experiments using human hair.
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Sample Shipping Stability: 9 methamphetamine-positive samples, 9 amphetamine-positive samples.
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Recovery: Not specified, likely laboratory experiments.
3. Number of Experts and Qualifications for Ground Truth
The document does not describe the use of human experts to establish ground truth in the traditional sense of image interpretation or clinical diagnosis. The ground truth for this device is based on analytical chemistry results.
- Ground Truth Establishment: The ground truth for the comparison studies is established using Liquid Chromatography/Mass Spectrometry/Mass Spectrometry (LC/MS/MS), which is the "preferred confirmatory method" for drug testing in hair. This is an objective chemical analysis method, not reliant on expert interpretation of observational data.
4. Adjudication Method for the Test Set
No adjudication method (like 2+1 or 3+1 consensus) is applicable or mentioned. The ground truth is established by a quantitative chemical analysis (LC/MS/MS). Discrepancies between the HEIA and LC/MS/MS results are analyzed and explained by the difference in sample preparation (washing for LC/MS/MS, no washing for HEIA screening), rather than resolved by expert consensus.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
No MRMC study was done or is applicable for this type of in vitro diagnostic device. This device is an automated immunoassay for preliminary detection of substances, not an imaging or interpretive diagnostic tool that involves human readers' performance with and without AI assistance.
6. Standalone (Algorithm Only) Performance
The "standalone" performance is essentially what is reported. The Psychemedics HEIA itself is the "algorithm" (the immunoassay system). Its performance is directly compared to the gold standard (LC/MS/MS) without human intervention in the interpretation of the HEIA signal. The entire document focuses on the performance of the device itself.
7. Type of Ground Truth Used
The primary ground truth used is objective chemical analysis via Liquid Chromatography/Mass Spectrometry/Mass Spectrometry (LC/MS/MS). For precision studies, it involved spiking negative hair with known concentrations of analytes, confirmed by LC/MS/MS validated calibrators and control solutions.
8. Sample Size for the Training Set
The document does not explicitly describe a "training set" in the context of machine learning, as this is an immunoassay device, not an AI/ML algorithm that is 'trained.' The device is a chemical system with reagents. Its method development and optimization would involve various experiments, but these are not referred to as a "training set" in the common AI/ML terminology.
9. How Ground Truth for the Training Set Was Established
Since there isn't a "training set" in the AI/ML sense, this question is not directly applicable. The development and calibration of the immunoassay reagents (anti-methamphetamine monoclonal antibody, methamphetamine labeled recombinant G6PDH, etc.) would involve analytical methods to ensure their specificity and sensitivity. The calibrators and control materials are prepared using drug stocks purchased from commercial vendors with certificates of analysis (Page 10), which serves as the reference for established concentrations.
§ 862.3610 Methamphetamine test system.
(a)
Identification. A methamphetamine test system is a device intended to measure methamphetamine, a central nervous system stimulating drug, in serum, plasma, and urine. Measurements obtained by this device are used in the diagnosis and treatment of methamphetamine use or overdose.(b)
Classification. Class II (special controls). A methamphetamine test system is not exempt if it is intended for any use other than employment or insurance testing or is intended for Federal drug testing programs. The device is exempt from the premarket notification procedures in subpart E of part 807 of this chapter subject to the limitations in § 862.9, provided the test system is intended for employment and insurance testing and includes a statement in the labeling that the device is intended solely for use in employment and insurance testing, and does not include devices intended for Federal drug testing programs (e.g., programs run by the Substance Abuse and Mental Health Services Administration (SAMHSA), the Department of Transportation (DOT), and the U.S. military).