Evaluation of a urine screen for acetaminophen.

Background: Acetaminophen (APAP) is a leading cause of fatal overdose. This study examined the performance characteristics of the Biosite Triage TOX Drug Screen qualitative APAP urine test (urine screen) in a clinical setting.

Methods: Paired urine and serum waste samples (collected within 2 hours of one another) were quantitatively analyzed for APAP concentration and compared to the urine screen results.

Results: A total of 191 paired samples met inclusion criteria. The urine screen did not report a negative result for the 21 samples with a serum APAP concentration of > or =10microg/mL and had a sensitivity of 100% (95% confidence interval [CI], 85-100%). The urine screen had a sensitivity of 96% (95% CI, 91-99%) and a specificity of 90% (95% CI, 82-95%) for detecting urine APAP concentrations > 5microg/mL by gas chromatograph mass spectroscopy (GCMS) methods, and a sensitivity of 81% (95% CI, 73-87%) and a specificity of 95% (95% CI, 85-98%) by high-pressure liquid chromatography (HPLC) methods.

Conclusions: The urine screen detected urine APAP concentrations with good accuracy and may be an effective screen to rule out acute APAP overdose in some circumstances. Its clinical utility is discussed.