Evaluating the appropriateness of digoxin level monitoring

Background: Digoxin level determinations can be useful clinically in patien ts receiving digoxin therapy but are sometimes misused. Methods: Explicit appropriateness criteria were adapted from previously pub lished criteria and revised using local expert opinion. They were then used to evaluate the appropriateness of random samples of inpatient and outpati ent serum digoxin levels. Overall agreement between reviewers regarding app ropriateness was good (kappa = 0.65). Patients in the study included 162 in patients in whom 224 digoxin levels were measured and 117 outpatients in wh om 130 digoxin levels were measured during a 6-month period. The main outco me measure was the proportion of digoxin levels with an appropriate indicat ion. Results: Among inpatient levels, only 16% (95% confidence intervals [CI], 1 1%-20%) were appropriate. Of the 189 digoxin levels considered inappropriat e, only 26 (14%) had a result of 2.3 nmol/L or more (greater than or equal to 1.8 ng/mt). None of these levels resulted in an important change in ther apy, and no patient had a toxic reaction to the therapy. Among inappropriat e levels, daily routine monitoring accounted for 78%. Of the 130 outpatient levels, 52% (95% CI, 44%-61%) were appropriate. Of 62 inappropriate levels , only 4 (6%) had a result of 2.3 nmol/L or more (greater than or equal to 1.8 ng/mL). One result led to a change in therapy, but none of the patients were believed to experience a toxic reaction. Among the inappropriate leve ls, 87% of patients underwent early routine monitoring before a steady stat e was achieved. Conclusions: A high proportion of digoxin levels were inappropriate, partic ularly among inpatients. In both groups, the primary reason tests were judg ed inappropriate was early routine monitoring. Few inappropriate tests resu lted in important data. Interventions to improve the use of digoxin levels could potentially save substantial resources without missing important clin ical results.