Preanalytical phase in haematology

Abstract

The preanalytical phase is particularly important in haematology, where counts of particles and cells are performed in whole anticoagulated blood. The correct use and concentration of anticoagulant is mandatory to avoid spurious results, which can influence clinical decision. EDTA is the anticoagulant of choice, but it has some limits, especially for preserving stability and shape of platelets. Stability of haematological parameters is high, with the exception of leukocytes and reticulocytes. However, stability (and instrumental precision) should be evaluated together with biological variability and individuality index of various haematological parameters. Hematological tests are also influenced and interfered by high amounts of lipids and chylomicrons. The mixing procedure of the tubes after blood drawing and before analysis is also crucial for obtaining correct and valid data. There are some examples of interferences on automated haematological analysers which are used for diagnosing and screening pathological conditions. Cryoglobulins and erythrocytes parasites can induce spurious results of WBC, RBC and PLT, but the repeatability of these interferences could be used for alerting the pathologist and could reveal the presence of pathological proteins or blood parasites. New parameters have been proposed by modern haematological analysers, directly defined or calculated from traditional measures, but the clinical impact of these new parameters is often dependent on preanalytical variables.