DIAGNOSTIC ACCURACY OF DRUG SCREENING IMMUNOASSAYS IN DRUG FACILITATED CRIMES

Abstract

Objective: To determine the diagnostic accuracy of immunoassays in drug screening as required in emergency for the rapid diagnosis of drug intoxication in travel related crimes.

Study Design: Diagnostic accuracy study.

Place and Duration of Study: department of Chemical Pathology and Endocrinology, Armed Forces Institute of
Pathology, Rawalpindi Pakistan, from Jul 2017 to Jun 2018.

Methodology: Sealed urine specimens of 77 patients with history of suspected intoxication in drugs facilitated
street crimes, received for toxicology screening were included in the study. All the specimens were analysed,
initially on immunoassay (index test) and then on Triple Quadrupole Liquid chromatography–Mass spectrometry (reference standard). Benzodiazepine being the main class of drugs involved in travel related crimes, diagnostic accuracy of immunoassay technique was assessed for these by calculating its sensitivity, specificity, positive predictive value and negative predictive value.

Results: Victims were predominantly males and public transportation was the most common mode of transport. The most commonly used drug was Lorazepam. Immunoassay failed to detect few cases who were shown to be intoxicated with benzodiazepines by liquid-chromatography tandem mass spectrometry. The false negative rate was 4.9%. Only one false positive case was observed. The accuracy was calculated to be 94.8% with sensitivity of 95.08% and specificity of 93.7%.

Conclusion: Immunoassay was found reliable for rapid testing in drug facilitated intoxication cases. However
critical decision making should be done cautiously keeping in mind the limitations associated with these
screening procedures.