Detection of methamphetamine in sweat by EIA and GC-MS

Area of Science:

• Forensic Toxicology
• Analytical Chemistry
• Biochemistry

Background:

• Sweat analysis offers a non-invasive method for drug monitoring.
• The PharmChekTM sweat patch is a viable tool for collecting sweat samples.
• Accurate detection of methamphetamine in sweat is crucial for clinical and forensic applications.

Purpose of the Study:

• To develop and validate a modified enzyme immunoassay (EIA) for quantifying methamphetamine in sweat collected via the PharmChekTM patch.
• To assess the assay's cross-reactivity, sensitivity, specificity, and precision.
• To establish an optimal cutoff concentration for reliable methamphetamine detection.

Main Methods:

• Sweat samples were collected using the PharmChekTM patch.
• A solid-phase, enzyme immunoassay was adapted for methamphetamine analysis.
• Gas chromatography-mass spectrometry (GC-MS) was used as the reference standard for validation.
• Receiver operating characteristic (ROC) analysis determined the optimal cutoff concentration.

Main Results:

• The EIA showed high specificity, with notable cross-reactivity to MDMA (144%) and d-amphetamine (30%).
• An optimal cutoff of 10 ng/mL amphetamine equivalents yielded 84.5% sensitivity and 93.2% specificity versus GC-MS.
• The overall analysis system achieved 85% clinical sensitivity and 100% specificity in volunteer studies.
• Two adulterants (tile cleaner, cough syrup) produced false positives, highlighting the need for confirmation.

Conclusions:

• The modified EIA using the PharmChekTM patch is a sensitive and specific method for detecting methamphetamine in sweat.
• The assay provides reliable results with good precision and accuracy, suitable for drug monitoring.
• Confirmation with GC-MS is recommended to rule out potential false positives from specific adulterants.