Background: Thallium (Tl), lead and steroid exposures were reported as a result of street drug consumption such as heroin and cocaine. 

Objective: This study aimed to compare the values of qualitative and quantitative assays for detecting Tl as an adulterant in opioid-like compound drug users.

Methods: This case-control study was conducted throughout a specified time bracket ranging from May 2015 to November 2015 in Imam Reza Hospital, Mashhad, Iran. In general, urine thallium samples for 100 opioid overdosed subjects with a history of chronic opioid use and 50 non-drug users were studied. Qualitative 24 hours-urinary-thallium-level (QL) and quantitative 24 hours-urinary-thallium-level (QT) were conducted in both groups. Independent-samples t-test and Spearman’s Coefficient were applied for analytical purposes. SPSS software 16 was used to conduct statistical analyses with P values less than 0.05 regarded as significant. 

Results: A total of 150 cases were studied. Raw opium users accounted for 66% of the cases followed by mixed (28%) and heroin users (6%). Mean (SD) QT level for QL was 26.8 (1) μg/L, while it was 2.3 μg/L (0.4 μg/L) for negative QL, which was far below QL positive cases (p=0.002). The qualitative test showed more accuracy at higher quantitative levels. In all cases, qualitative test was fully sensitive (100%), highly specific (89%) with a positive likelihood ratio (PLR) of 9.1 and a negative likelihood ratio (NLR) of 0.

Conclusion: These results suggest that qualitative assays could be used with confidence in assessing Tl exposure in drug users. Physicians may easily and confidently use Tl qualitative tests in rehabilitation centers, where toxicology laboratories may not be available.


Keywords: Drug user, Thallium, Quantitative assay, Qualitative assay
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