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Validation of a rapid urine screening assay for cocaine use among pregnant emergency patients
E J Westdorp1, J A Salomone, D K Roberts
1School of Medicine, Department of Emergency Medicine, University of Missouri-Kansas City, Truman Medical Center, USA.
Objectives:
To determine the accuracy of the OnTrak rapid urine latex agglutination immunoassay (AIA) for testing pregnant ED patients for the cocaine metabolite benzoylecgonine (BE), and to determine the frequency of urine BE in pregnant ED patients and the association of test results with patient demographics.
Methods:
A test performance evaluation was conducted using an inception cohort of pregnant patients at an urban teaching hospital ED. Patients with positive urine chorionic gonadotropin tests who had adequate remaining urine samples were studied. Patient demographics, ED diagnoses, and assay results were recorded without patient identifiers. Urine was tested using the rapid AIA. The first 150 samples were confirmed using a second immunoassay and gas chromatography with a nitrogen phosphorus detector. All positive samples also were confirmed with thin-layer chromatography, and quantification by gas chromatography-mass spectrometry.
Results:
Twenty of 342 (5.9%, 95% CI 3.4-8.4%) pregnant patients had urine samples positive by AIA testing for BE. Confirmation testing demonstrated no false-positive or -negative AIA result. Positive test results were not associated with specific patient diagnoses or demographics.
Conclusions:
ED screening for cocaine use among pregnant patients can be accurately performed using the OnTrak AIA for BE. In the ED population screened, 5.9% of the pregnant women had urine samples positive for BE.