Reference method for platelet enumeration.

The main principle of enumerating platelets in automated hematology analyzer is electric resistance system. However, there have been an increasing number of instruments that can enumerate platelets by optical system. The use of a flow cytometry (FCM) employing monoclonal antibody has been under study for the enumeration of platelets in recent years. At its meeting held in April 2000, the International Society for Laboratory Hematology (ISLH) decided on a protocol to study the possibility of using, as reference method, a monoclonal antibody-employed FCM of enumerating platelets. In our present study, we obtained platelet count by the monoclonal antibody-employed method proposed by ISLH, and compared the result with platelet count obtained with an automated hematology analyzer XE-2100 (Standard counter at Scientific Division, Sysmex, Kobe, Japan) employing electric resistance system, and another platelet count obtained by optical system.

Evaluation of hematological values obtained with reference automated hematology analyzers of six manufacturers.

We evaluated assays of the same fresh blood samples with six different types of reference automated hematology analyzers developed by the following manufacturers: Beckman Coulter, Sysmex, Bayer, Abbott, Nihon Kohden and Horiba. Fresh whole blood samples treated with dipotassium ethylenediaminetetraacetic acid (EDTA K2) were collected from three healthy adult volunteers. The complete blood counts (CBC) including red blood cell count (RBC), hemoglobin (Hgb), hematocrit (Hct), mean corpuscular volume (MCV), white blood cell count (WBC), platelet count (Plt), reticulocyte percentage (Ret) and leukocyte differential counts including % neutrophils (Neu), % lymphocytes (Lym) and % monocytes (Mon) were surveyed with a reference automated hematology analyzer from each manufacturer. The process from sampling to analysis was performed according to procedures in hospital clinical laboratories. RBC, Hgb, Hct and MCV exhibited allowable differences within 5% of mean value among all instruments. Large differences greater than 10% of mean value in WBC, Neu and Lym between Horiba and other manufacturers, and in Plt between Nihon Kohden and other manufacturers, were observed. Ret and Mon exhibited large differences over 10% of mean value among almost all of the instruments tested. This survey suggests that all parameters exhibiting differences greater than 10% of mean value among instruments should be improved for clinical use to ensure good external quality control in blood cell counting and leukocyte differential counting using automated instruments.