Effect of data collection method on results of serum digoxin concentration audit

The appropriateness of serum digoxin concentration (SDC) orders was evaluated with respect to indication for use, sampling time, and action taken by physicians when the reported SDC was out of the normal therapeutic range; the effect of the two data-collection methods used (retrospective and concurrent audits) on the results was studied. Criteria for the appropriate use of SDCs were approved by the medical staff through the pharmacy and therapeutics committee. Patients on adult medicine services were entered into the study as daily SDC determinations were reported by the clinical laboratory. Most of the SDCs were evaluated using approved criteria by primary pharmacist clinicians who were concurrently monitoring drug therapy and participating with the treatment team. A retrospective audit of the same patients was conducted, using only chart review. A total of 134 SDCs involving 78 patients were evaluated. Concurrent-audit results indicated that 18.7% of the SDCs were ordered without an appropriate indication, 16.4% were sampled incorrectly with respect to proper timing, and 8.2% did not result in dosage adjustments when indicated. With respect to appropriate sampling time and overall use of SDCs, significantly more SDCs met the standards under concurrent audit than under retrospective audit. The retrospective chart review method of auditing may not detect as much pertinent information as is desirable.