Journal of analytical toxicology
-
Urine drug testing (UDT) is an emerging standard of care in the evaluation and treatment of chronic non-cancer pain patients with opioid analgesics. UDT may be used both to verify adherence with the opioid analgesic regimen and to monitor abstinence from non-prescribed or illicit controlled substances. In the former scenario, it is vital to determine whether the drug is present in the urine, even at low concentrations, because failure to detect the drug may lead to accusations of opioid abuse or diversion. ⋯ Examination of the raw data from these presumptive negative opiate screens revealed that, in many cases, the turbidity signal was greater than the signal obtained for the negative control, but less than the signal for the 300 ng/mL (morphine) threshold calibrator. A receiver operating characteristic curve generated for the reciprocal of the ratio of turbidity measurements in the patient specimens and negative (drug-free) controls, against the presence or absence of HC and/or HM by confirmatory analyses, produced an area under the curve of 0.910. We conclude that this opiate immunoassay has sufficient sensitivity to detect HC and/or HM in some urine specimens that screen presumptive negative for these commonly prescribed opiates at the established threshold.