An Evaluation of the Haema-Count MK-4S Platelet Counting System

The Haema-Count MK-4S system consists of an electronic platelet particle detector and a low-speed centrifuge to prepare platelet-rich plasma. It had greater day-to-day and within-day precision than the phase chamber reference method. In general, it had a good agreement on patient specimens but, in common with other automatic platelet-counting instruments, it was affected by abnormal proteins and by extremes of platelet size. Centrifugation was more rapid and neater than sedimentation in the preparation of platelet-rich plasma. It was not uniformly more accurate, and at high counts may have caused small losses; but in cases of very slow erythrocyte sedimentation it yielded more accurate counts than those obtainable by sedimentation. Users of automatic systems should be alert to occasional spurious counts, and a suitable chamber method should be available to investigate results in disagreement with clinical findings or with the estimate on differential smear.