Use of capillary blood count parameters in adults.

BACKGROUND AND OBJECTIVES: Capillary samples can provide blood for cell counts in haematologic patients and blood donors. However, some accept only values from venous blood. This study compares capillary and venous blood counts to verify the hypothesis that they are equivalent.
MATERIALS AND METHODS: We analysed 463 capillary (fingerstick) and venous blood samples from 428 adults of both sexes (71% haematologic patients, 29% potential blood and apheresis donors). Both samples were taken at the same time from each subject. Haemoglobin (Hb), haematocrit (Hct), white blood cells (WBC), platelets, red blood cells (RBC), mean corpuscular volume (MCV), mean corpuscular Hb (MCH) and mean corpuscular Hb concentration (MCHC) were measured using a haematology analyser (Advia 120, Bayer).
RESULTS: Capillary Hb, Hct, WBC, RBC, MCV and MCH were all significantly higher than the venous values [+0.2 mmol/l (+0.3 g/dl), +0.02 l/l (+2%), +0.2 x 10(9)/l, +0.1 x 10(12)/l, +3.1 fl and +0.01 fmol, respectively], whereas the capillary MCHC was lower (-0.6 mmol/l). There was no difference in platelets (-1 x 10(9)/l). Capillary Hb and Hct values were higher in patients with anaemia and polycythaemia, respectively. However, no significant differences occurred in severe thrombocytopenia.
CONCLUSION: In adult haematologic patients, however, only the differences in Hb and Hct values may be of clinical relevance. For potential blood and apheresis donors, Hb and platelet screening are equivalent with either capillary and venous blood using a haematology analyser.