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 prob-lems in the testing process in hospital and physician office laboratories, we examined the testing for serum total cholesterol (n 5 646) and potassium (n 5 732) 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, th