AUDIT EXPOSES FLAWED BLOOD-SAMPLING FOR DIGOXIN LEVELS

Therapeutic "digoxin level" monitoring in selected wards was audited. Time elapsing between the last dose and blood sampling was considered appropriate if greater-than-or-equal-to 6 h. If such details were not entered on the requisition, the maximum time elapsing was estimated as "appropriate" or "inappropriate" from the time samples were logged in to the laboratory and the time the last dose was entered in the patien t's treatment sheet. In 22 requisitions detailing sampling time, nine were considered inappropriate. In an additional 150 instances, timing was estimated as inappropriate in 45. Among the 118 requests where tim ing (estimated or labelled) was appropriate, available plasma digoxin concentrations yielded a mean of 1.0 nM, compared to 1.6 nM in the cor responding 54 patients with premature sampling; this difference was bo th clinically and statistically significant (95% confidence limits 0.8 -1.2 and 1.3-1.9 nM, respectively, p < 0.001). Premature blood samplin g for digoxin levels was common and associated with higher concentrati ons than when appropriate. Such inappropriate timing may not have seri ous consequences, but digoxin levels are a matter of record and are us ed for teaching; due attention to timing could provide more reliable i nformation and avoid wasting valuable resources.