Riboflavin as a tracer of medication compliance

Three experiments were conducted to evaluate the accuracy of urine ultraviolet fluorescent tests for riboflavin, which has been used as a tracer for medication compliance in several clinical drug trials. Observer accuracy in discriminating riboflavin-positive or negative urine samples was found to vary with the method of observation, dose of riboflavin, observer experience, and time postingestion. The results showed that, while the 5-mg dose used in previous clinical trials was too small to permit reliable assessment of compliance, larger doses of riboflavin could produce nearly 100% accuracy for minimally trained observers who used a matching-to-sample observation procedure. The findings are discussed in terms of the potential clinical and research applications of this type of simple but reliable compliance assessment procedure.