The clinical utility and adverse consequences of the complete blood count in an internal medicine department

The clinical utility and adverse consequences of the admission and follow-up complete blood count (CBC) in hospitalised patients are unclear. We selected 273 patients chosen from a single internal medicine department. To determine clinical utility and adverse consequences, we interviewed attending physicians and reviewed patients' charts. There were 12 (4.4%) patients hospitalised because of the CBC test result, six referred appropriately with a low haemoglobin concentration found in outpatient clinics and six (2.2%) patients (95% confidence interval 0.8-4.7%) inappropriately hospitalised because of incidental findings. In the hospital, according to the physicians, nearly all treatment changes made were for blood transfusions that were not indicated in 18 (6.6%) patients (95% confidence interval 4.0-10.2%). The only unexpected findings were in four patients with an indication for a blood transfusion admitted with an acute coronary syndrome and haemoglobin values 8-9.9 g/dL, and in one bedridden patient with dementia with acute myeloid leukaemia. There were 290 follow-up CBC tests not resulting in differential treatment. We conclude that admission CBC tests commonly lead to adverse consequences, due to physician errors in judgement. Incidental findings of anaemia justify CBC testing in patients with an acute coronary event. The rare patient with an incidental finding resulting in appropriate differential treatment might justify non-selective admission CBC counts, if physician education reduces the rate of inappropriate blood transfusions.