Short-term and long-term intra-individual variations and critical differences of haematological laboratory parameters.

The complete blood cell count and the differential leukocyte count have been studied for their variations within-one-day and during one week (short-term variations) and during a period of six months (long-term variations) with an automatic haematology analyser (H-6000, Technicon), in which some new parameters (large unstained cells, high peroxidase cells, red cell distribution width, platelet distribution width, mean platelet volume, plateletcrit) are included. The influence of external factors such as sex-differences, smoking/non-smoking, use of oral contraceptives etc. have also been studied. It appears that the use of critical differences together with haematological data improves the value of these parameters in diagnosis and treatment of patients.