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The Methamphetamine Enzyme Immunoassays for Drugs of Abuse in Oral Fluid is a homogeneous enzyme immunoassay system to detect methamphetamine in human saliva with a cutoff of 45 ng/mL when testing oral fluid specimen collected with Salivette collector (manufactured by Sarstedt) and diluted with 1 mL of buffer. The calibrators and controls of the analyte (d-methamphetamine) are prepared with oral fluid buffer so that it can be used to verify and validate the assay. The assay is intended for use in the qualitative determination for methamphetamine. The assay is designed for professional use with a number of automated clinical chemistry analyzers.

The Oral Fluid Methamphetamine Enzyme Immunoassay is a homogeneous enzyme immunoassay system provides only a preliminary analytical test result. A more specific alternative chemical method must be used to obtain a confirmed analytical result. Gas chromatography/mass spectrometry (GC/MS) is the preferred confirmatory method. Clinical consideration and professional judgment should be applied to any drug-of-abuse test result, particularly when preliminary positive results are used.

LZI's Oral Fluid Methamphetamine Enzyme Immunoassay is a ready-to-use, liquid reagent, homogeneous enzyme immunoassay. The assay uses specific antibodies that can detect methamphetamine in oral fluid with minimal cross-reactivity to various, common prescription drugs and abused drugs. The assay is based on competition between drug labeled with glucose-6-phosphate dehydrogenase (G6PDH) enzyme and free drug from the saliva sample for a fixed amount of specific antibody. In the absence of free drug from the saliva sample the specific antibody binds to the drug labeled G6PDH enzyme causing a decrease in enzyme activity. It is therefore the drug concentration is proportional to the enzyme activity. The G6PDH enzyme activity is determined spectrophotometrically at 340 nm by measuring its ability to covert nicotinamide adenine dinucleotide (NAD) to NADH.

Here's a breakdown of the acceptance criteria and study information for the LZI Oral Fluid Methamphetamine Homogeneous Enzyme Immunoassay, based on the provided text:

1. Table of Acceptance Criteria and Reported Device Performance

Explanation of "Acceptance Criteria (Implied)": The document doesn't explicitly state quantitative acceptance criteria for the LZI device. Instead, it demonstrates substantial equivalence to a predicate device (OraSure Methamphetamine Intercept® Micro-plate EIA) and other LZI test systems by showing comparable performance. Therefore, the predicate's reported performance (e.g., 98% accuracy agreement) serves as the de-facto benchmark for acceptance of the new device. The precision data for the LZI device is presented without an explicit "criteria" column, but the low %CV values indicate good precision, which is generally expected for such devices.

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

• Sample Size (Clinical Patients): 112 for the LZI Oral Fluid Methamphetamine Assay. (The predicate device study used n=50 clinical samples).
• Data Provenance: The document does not explicitly state the country of origin. It is a retrospective study, as it uses collected clinical patient samples and compares the assay results to a confirmatory method (GC/MS).

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

• This information is not provided in the document.
• The ground truth was established using an analytical method (GC/MS), not through expert interpretation of images or clinical assessments by a panel of human experts. Therefore, the concept of "number of experts" or their qualifications is not relevant here.

4. Adjudication Method for the Test Set

• None. The primary method for ground truth establishment was Gas Chromatography/Mass Spectrometry (GC/MS), which is an objective chemical analysis method, not requiring adjudication by human readers.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study was Done

• No. This is an in vitro diagnostic device (immunoassay) designed to provide an analytical result based on a chemical reaction, not an imaging or diagnostic AI tool that assists human readers. Therefore, an MRMC study is not applicable or mentioned.

6. If a Standalone Study (Algorithm Only Without Human-in-the-Loop Performance) was Done

• Yes. The performance data presented (accuracy vs. GC/MS, precision) are for the LZI Oral Fluid Methamphetamine Enzyme Immunoassay operating as a standalone analytical device. The "algorithm" in this context is the biochemical reaction of the immunoassay itself, and its performance is evaluated independently of human interpretation, beyond the professional use and judgment required in applying the results.

7. The Type of Ground Truth Used

• Analytical Confirmation: Gas Chromatography/Mass Spectrometry (GC/MS). This is explicitly stated as the "preferred confirmatory method" and the method against which the device's accuracy was compared.

8. The Sample Size for the Training Set

• This information is not applicable/provided for this type of device. The LZI Oral Fluid Methamphetamine Homogeneous Enzyme Immunoassay is an immunoassay, not a machine learning or AI algorithm that undergoes "training" on a data set in the conventional sense. Its performance is based on its chemical design and validation against known standards and clinical samples.

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

• As mentioned above, the concept of a "training set" with established ground truth is not applicable for this immunoassay device. The device's underlying chemical principles and components are developed and optimized (not "trained") according to biochemical and analytical chemistry principles. Its performance is then validated using calibrators, controls, and clinical samples, with GC/MS as the gold standard for confirmation.

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