Desirable standards of performance for therapeutic drug monitoring.

Therapeutic drug monitoring is an important aspect of clinical chemistry for which no objective analytical goals yet exist. Based on fundamental pharmacokinetic theory, and the current consensus strategy for analytical goal-setting for precision based upon biological variation, a theoretical model allows derivation of the goal that: analytical CV less than or equal to 1/4 [(2T/t - 1)/(2T/t + 1)] X 100%, where T is the time interval between doses, and t is the average elimination half-life. Using published data on half-lives, I have derived goals for analysis for (e.g.) digoxin, lithium, some antiepileptic drugs, and theophylline. The goal for accuracy proposed is that methods should have no bias and should generate true values. Goals for precision should therefore be viewed as goals for total analytical error.