Evaluation of DUS to toxicological screening using lateral flow immunochromatography

Abstract

INTRODUCTION: Toxicological screening is a crucial step for diagnosing drug poisoning. Lateral flow immunochromatography is a simple, affordable, and rapid technique that aids in emergency diagnosis of acute poisoning and drug abuse monitoring. One of the main biological samples tested by this technique is urine, as it is most commonly used to confirm recent exposure to substances. Dried urine spots (DUS) have gained prominence as a method of collection due to its advantages, which include simpler storage conditions and easier transport, resulting in a reduction in the overall cost of analysis. METHODS: Urine samples from patients with confirmed poisoning by drugs were applied to filter paper cards to be used as DUS. Resuspended samples were analyzed through lateral flow immunochromatography. The results of the DUS screening tests were compared to the results of testing samples in their liquid form. Sensitivity and stability tests were performed using a solution of amitriptyline with a known concentration. Positive predictive value (PPV), negative predictive value (NPV), and efficiency were the metrics used to analyze the method’s application. RESULTS: Sensitivity tests showed a 20% increased cutoff compared to liquid urine; DUS was stable for at least 3 days at room temperature. PPV had values of 100%; NPV values varied from 58% to 100%. Efficiency values varied from 75% to 100%. These results suggest that this DUS processing method is efficient and specific but generally less sensitive, it rarely gives false positives but may miss some true positives. CONCLUSIONS: DUS was found to be efficient in terms of sample storage and stability, and the DUS desorption protocol showed efficiency and specificity in performing rapid toxicological screening tests among the techniques studied.