Economic and Outcome Issues for Therapeutic Drug Monitoring in Medicine

Abstract

Outcome and economic studies pertaining to the use of therapeutic drug monitoring (TDM) are summarized. The studies were classified by a 2 × 2 matrix comprised of process, outcome, system-related variables, and patient-centered variables. Two hundred forty-seven studies conducted from 1974 to 1994, culled from eight summary sources, were reviewed. Almost 75% of the studies reported system-related, not patient-centered, measures for assessing the value of TDM; nearly the same percentage evaluated processes as opposed to outcome measures. Studies comparing TDM to non-TDM populations generally showed that TDM as an intervention reduced the rate of undesirable system-related variables by 50% and increased the rate of desirable system-related variables by 100%. For patient-centered variables, TDM was less dramatic, decreasing the rate of undesirable variables by 15% to 50%. Only 8% of the studies examined economic variables. TDM-influenced changes in process variables resulted in a projected mean annual savings of $37,000. The few studies available of cost-benefit analysis focused on aminoglycosides and showed that TDM yielded a range from 4:1 to 52:1 in benefit-to-cost ratio. Most studies have limitations that include small sample size, short study periods to predict long-term outcomes, no long-term follow-up, and designs for noncontrolled study.