Practical experience with a quality control procedure using retained patient specimens on Technicon H1 and COULTER S 880.

External quality assessment and internal quality control in hematology is complicated by the lack of good control materials. Commercial materials do not always behave as patient blood and they are expensive. Patient specimens are unstable, but may be used either within certain time limits or as in Bull's moving average for red cell indices. We have used retained patient specimens for internal quality control supplemented by a commercial control material. Three patient-specimens were run alternatively on a Technicon H1 and a Coulter 880 at regular intervals. The variations for each instrument and between instrument were computed. We used the 2 of 3 (2s) control rule. Our conclusion is that the Coulter 880 had an overall better performance than the Technicon H1 when using retained patient specimens. But both instruments practically met suggested analytical goals.