Cost containment and labor-intensive tests. The case of the leukocyte differential count.

We conducted an analysis of the use of the leukocyte differential count to determine (1) the services ordering the largest numbers of tests, (2) the proportion of differentials that were clinically justifiable and useful, and (3) the potential for real cost savings as opposed to reduction in charges if unjustified differentials could be eliminated. The sources of all laboratory requisitions during three nonconsecutive weeks were determined; criteria for test justifiability were established; an audit of a random sample of medical records was conducted on two services obtaining the most tests; and a time-motion study was undertaken in the hospital hematology laboratory. Forty-seven percent of differentials were obtained on medical and surgical inpatients and only 10% in the medical clinics. Forty-eight percent and 62% of differentials on the medical and surgical services, respectively, were unjustifiable , making up 26% of all differentials done in the hospital laboratory. Test results appear to have affected patient management in less than 3% of patients; no unjustified test altered a patient's diagnosis or therapy. Elimination of only "unjustified" medical and surgical differentials would permit a reduction of 1.8 full-time equivalent positions from the hospital laboratory. The leukocyte differential is over-used, only occasionally useful, and amenable to real cost reduction.