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

The intra-individual variations of 9 coagulation parameters were studied during short-term (within-one-day) and long-term (six months) periods. Two groups of healthy individuals (viz. 60 and 274 persons) were involved. Moreover, critical differences have been calculated from the total variations, comprising both biological and analytical variations. The influences of external factors such as sex, smoking and the use of oral contraceptives have also been studied. The variability and critical differences found in coagulation parameters in this study appeared to be of the same order as those observed in parameters usually determined in clinical chemistry and haematology. The application of critical differences in the evaluation and use of laboratory data, also in coagulation studies, enhances the objectivity of the judgement. Moreover, in the follow-up of patients the sensitivity of the parameters is increased.