System to monitor a portion of the total testing process in medical clinics and laboratories: evaluation of a split-specimen design.

To evaluate a split-specimen design to identify problems in the testing process in hospital and physician office laboratories, we examined the testing for serum total cholesterol (n = 646) and potassium (n = 732) at 11 medical clinics evaluating 30-199 patients (mean, 125). Clinic personnel collected three tubes of blood from each patient. One specimen was processed routinely, the second was sent to a referral laboratory (RL), and the third specimen was sent to a holding facility for storage. The corresponding stored sample was retrieved and divided into three audit samples randomly and when result difference for the first two specimens exceeded critical values; one audit sample was sent to the original participant, the second to the RL, and the third to a referee laboratory. When three criteria were used, the result discrepancy rates were 2.5-8.7% for potassium and 1.5-4.6% for cholesterol. The split-specimen design could be implemented and evaluated as a monitoring system for a portion of the testing process.