Objective: Several drugs can cause analytical interference in clinical laboratory tests.  To prevent errors in clinical judgment as a result of false data, we investigated the information available on the interference of ethical drugs in these tests.
Methods: We examined the information available by collecting and evaluating information in package insert leaflets, collecting and evaluating clinical data on three drugs (bucillamin, captopril, and epalrestat) which affect clinical laboratory test results, and conducting a questionnaire survey of healthcare workers.
Results: From the information available on package inserts, 227 drugs were identified as having the potential to interfere with the chemical reactions used in clinical laboratory tests.  However, the insert information is not sufficient for use in clinical settings because the frequency rate and causative factors of interference are not stated clearly.  The clinical survey results reveal that 40% of patients taking bucillamine and 20% of patients taking epalrestat tested false-positive for urinary ketones.  According to the questionnaire results, medical technologists were more interested than pharmacists and physicians in how drugs affect clinical laboratory tests.
Conclusion: The information currently available on the interference of drugs in clinical laboratory tests is problematical, and it is therefore necessary to collect more clinical data for the proper interpretation and evaluation of abnormal laboratory values.