The White Blood Cell and Differential Count

The simplest test is the WBC count and differential. White cells can be counted manually in specially designed chambers (Neubauer) or with automated counters. The latter are widely used, offering the advantage of higher accuracy and speed over manual techniques. To determine the differential, a drop of blood is thinly spread over a glass slide, air dried, and stained with a Romanofsky stain, most commonly the Wright or May-Grunewald-Giemsa technique. Two hundred cells are then counted and classified. Machines have been developed to perform automated differential counts, but they are still inferior to manual techniques as far as reliability and ability to discover morphologic abnormalities.