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The LZI Amphetamines 500 Enzyme Immunoassay is intended for the qualitative and semi-quantitative determination of amphetamine and methamphetamine in human urine, at a cutoff value of 500 ng/mL when calibrated with d-methamphetamine. The assay is designed for professional use with a number of automated clinical chemistry analyzers.

The LZI Amphetamines 500 Drugs of Abuse (DAU) Calibrators are for use as calibrators in the qualitative and semi-quantitative calibration of the LZI Amphetamines Enzyme Immunoassay.

The LZI Amphetamines 500 Drugs of Abuse (DAU) Controls are for use as assayed quality control materials to monitor the precision of the LZI Amphetamines 500 Enzyme Immunoassay.

The assay provides only a preliminary analytical result. A more specific alternative chemical method must be used in order to obtain a confirmed analytical result. Gas or liquid chromatography/mass spectrometry (GC/MS or LC/MS) is the preferred confirmatory method). Clinical consideration and professional judgment should be exercised with any drug of abuse test result, particularly when the preliminary test result is positive.

The LZI Amphetamines 500 assay is a homogeneous enzyme immunoassay with readyto-use liguid reagent. The assay is based on competition between drug in the sample and drug labeled with the enzyme glucose-6-phosphate dehydrogenase (G6PDH) for a fixed amount of antibody in the reagent. Enzyme activity decreases upon binding to the antibody, and the drug concentration in the sample is measured in terms of enzyme activity. In the absence of drug in the sample, amphetamines-labeled G6PDH conjugate is bound to antibody, and the enzyme activity is inhibited. On the other hand, when free drug is present in the sample, antibody would bind to free drug, the unbound amphetamines-labeled G6PDH then exhibits its maximal enzyme activity. Active enzyme converts nicotinamide adenine dinucleotide (NAD) to NADH, resulting in an absorbance change that can be measured spectrophotometrically at 340 nm.

The LZI Amphetamines 500 Enzyme Immunoassay is a kit comprised of two reagents, an R1 and R2 which are bottled separately but sold together within the kit.

The Ri solution contains two mouse monoclonal anti-amphetamines antibodies, glucose-6-phosphate (G6P) nicotinamide adenine dinucleotide (NAD), stabilizers, and sodium azide (0.09%) as a preservative. The R2 solution contains glucose-6-phosphate dehydrogenase (G6PDH) labeled with amphetamines in buffer with sodium azide (0.09%) as preservative.

The LZI Amphetamines 500 Enzyme Immunoassay calibrators and controls contain 0, 250, 375, 500, 625, 1000, or 2000 ng/mL of d-methamphetamine in human urine with sodium azide (0.09%) as preservative. These five calibrators and two controls are sold as individual bottles.

Acceptance Criteria and Device Performance for LZI Amphetamines 500 Enzyme Immunoassay

This document outlines the acceptance criteria and reported device performance for the LZI Amphetamines 500 Enzyme Immunoassay, based on the provided 510(k) summary.

1. Table of Acceptance Criteria and Reported Device Performance

The provided document details various performance characteristics, primarily precision and method comparison (agreement with GC/MS). The acceptance criteria are not explicitly stated as "acceptance criteria" but are implied by the reported performance, with the device demonstrating high agreement rates with confirmatory methods for positive and negative samples, and good precision metrics.

Implicit Acceptance Criteria (based on reported performance for a device seeking substantial equivalence):

• High agreement (e.g., 96-100%) with a confirmatory method (GC/MS) for both positive and negative clinical samples.
• Reliable qualitative determination (positive/negative) around the 500 ng/mL cutoff, with minimal misclassification at concentrations significantly above or below the cutoff.
• Acceptable precision (low coefficient of variation (CV%) and standard deviation (SD)) for semi-quantitative measurements across various concentrations, indicating consistent results within and between runs.

Table 1: Device Performance Summary for LZI Amphetamines 500 Enzyme Immunoassay

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

• Test Set Sample Size:
  • Precision Studies: 88 determinations for each concentration level (22 determinations per run across 4 runs). This applies to both d-methamphetamine and d-amphetamine.
  • Method Comparison - Clinical Samples:
    • d-methamphetamine: 86 clinical unaltered samples.
    • d-amphetamine: 111 clinical unaltered samples.
• Data Provenance: The document does not explicitly state the country of origin. The samples for method comparison are referred to as "clinical unaltered samples," implying they were collected from human subjects in a clinical setting. It is retrospective as these are pre-existing clinical samples used for evaluation.

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

The document does not specify the number of experts or their qualifications for establishing ground truth. Instead, the ground truth for the clinical samples was established using "Gas or liquid chromatography/mass spectrometry (GC/MS or LC/MS)," which is cited as the "preferred confirmatory method." This is a laboratory-based, objective chemical analysis, rather than expert interpretation.

4. Adjudication Method for the Test Set

Since the ground truth for the method comparison studies was established by a laboratory-based confirmatory method (GC/MS or LC/MS) and not by expert interpretation, there was no adjudication method (e.g., 2+1, 3+1, none) in the traditional sense. The results of the immunoassay were compared directly against the quantitative analytical results of the confirmatory method.

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

There is no mention of a Multi-Reader Multi-Case (MRMC) comparative effectiveness study being done in this 510(k) summary. This type of study typically applies to imaging or diagnostic devices where human interpretation is a key component, which is not the primary focus of this immunoassay device approval. The study focuses on the device's analytical performance.

6. Standalone Performance Study

Yes, a standalone study was done. The entire performance characterization presented (precision, limit of detection, linearity, method comparison, and cross-reactivity) describes the algorithm/device-only performance without human intervention in the assay execution or primary result interpretation. The device's output (quantitative or qualitative result) is directly compared to the ground truth.

7. Type of Ground Truth Used

The type of ground truth used for the clinical samples in the method comparison study was laboratory-based confirmatory analysis, specifically Gas Chromatography/Mass Spectrometry (GC/MS) or Liquid Chromatography/Mass Spectrometry (LC/MS). For precision studies, the "ground truth" was established by preparing known concentrations of d-methamphetamine and d-amphetamine in urine. For cross-reactivity, known interfering substances were added.

8. Sample Size for the Training Set

The document does not provide information regarding a separate "training set" or its sample size. This type of product (a homogeneous enzyme immunoassay) is typically developed and optimized during a multi-stage R&D process, but the performance studies described in a 510(k) summary generally focus on the validation of the final, locked-down device using a distinct test set. The calibrators and controls used for the assay itself are part of the device's operational design, not a "training set" in the context of machine learning.

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

As no "training set" is explicitly mentioned in the context of a machine learning-like development process, information on how its ground truth was established is not available in this document. The document describes the assay's principle (competition between drug and drug-labeled enzyme for antibody binding) as a chemical reaction rather than an algorithm that requires a training set. Ground truth for internal development and optimization would have involved similar analytical methods (e.g., gravimetric preparation, GC/MS) for defining known concentrations and evaluating initial formulations.

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