Utility of pediatric urinalysis to screen for paracetamol intake: a preliminary study

Objective: To explore whether urinalysis to screen for paracetamol intake, following the

same procedure as is used for blood analysis, would be useful.

Methods: Retrospective cross-sectional, descriptive-analytical study of a random sample

of patients for whom urine tests were ordered in an emergency department. The data

were classified into 2 groups, according to whether the patients had or had not taken a

therapeutic dose of paracetamol during the previous 24 hours. Paracetamol

concentration in urine was measured for all patients. We compared the percentages of

patients with positive findings between groups and calculated the sensitivity, specificity,

and positive and negative predictive values of urinalysis for paracetamol.

Results: A total of 161 children between the ages of 17 days and 17 years were included;

83 had taken paracetamol and 78 had not. Urine tests were positive for all patients in the

first group and for 7.7% in the second group. The sensitivity of the test was 100% (95%

confidence interval [CI], 95.6%-100%) and the specificity was 92.31% (95% CI, 84.22%-

96.43%). No patient who had taken paracetamol had a negative urine test (negative

predictive value, 100%; 95% CI, 94.93%-100%).

Conclusions: Urinalysis to screen for paracetamol intake in the previous 24 hours is

useful. A negative result would make blood testing unnecessary. This approach to

screening would clearly benefit young children who may have taken the medication

accidentally or adolescents who may have used it to attempt suicide.