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EFFECT OF METHADONE ON HUMAN PREGNANCY TESTS

Summary.: A prospective study of four commercially available pregnancy tests was performed on 309 urine specimens specifically selected from patients in a methadone study group. The accuracy of the various tests, based on the total number of correct test results, was 99·7% for the Pregnosticon ® and UCG® tube tests, 96·4% for the Pregnosticon ® slide test and 81·2% for the Gravindex® slide test. Analysis of the test data revealed that most of the false positive test results were recorded on specimens received from patients on 100 mg methadone, or more, per day. Semiquantitative thin-layer chromatography suggested that methadone metabolites could, at least in part, be responsible for the inhibition of latex particle agglutination and incorrect test results.