Predictive properties of a qualitative urine acetaminophen screen in patients with self-poisoning.
OBJECTIVE
Screening for acetaminophen toxicity is recommended in almost all cases of self poisoning. We compared a qualitative urine acetaminophen screen to the quantitative serum acetaminophen to test the hypothesis that a negative urine acetaminophen screen would be predictive of a negative serum acetaminophen level.


METHODS
All adults with intentional ingestions evaluated in our Emergency Department during 1995 were retrospectively identified based on Emergency Department International Classification of Disease--9th edition codes. Laboratory data from each patient including serum and urine toxicologic assays were examined. Predictive properties of urine acetaminophen screens for serum acetaminophen were evaluated.


RESULTS
A total of 88 patients were identified who had both a serum acetaminophen and a urine acetaminophen performed. The sensitivity of the urine acetaminophen screen was 100% (95% CI 72-100%) and the specificity was 87% (95% CI 80-95%). All patients with negative urine acetaminophen screens had negative serum acetaminophen levels (negative predictive value 100%; 95% CI 96-100%). Accuracy of the urine acetaminophen screen was 89%.


CONCLUSIONS
A negative urine acetaminophen screen was highly predictive of negative serum acetaminophen levels. It is possible that negative urine acetaminophen screens may obviate the need for 4-hour quantitative serum levels. Further validation in a prospective study is needed.
Perrone
J
J
Hospital of the University of Pennsylvania, Department of Emergency Medicine, Philadelphia 19104, USA. Jeanmari@mail.med.upenn.edu
Hollander
J E
JE
Shaw
L
L
De Roos
F
F
D000082:Acetaminophen / Q000097:blood / Q000506:poisoning / Q000652:urine*; D000293:Adolescent; D000328:Adult; D000368:Aged; D062787:Drug Overdose / Q000097:blood / Q000175:diagnosis* / Q000652:urine; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011041:Poisoning / Q000097:blood / Q000652:urine*; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013406:Suicide, Attempted; D016482:Urinalysis / Q000379:methods
D000082:Acetaminophen