Haemoglobinometry in general practice

Haemoglobinometry as a primary point-of-care test is well established. This study was undertaken to assess whether haemoglobinometry by itself provides an adequate haematological screening procedure in general practice. In a series of 500 sequential blood counts received by the central hospital laboratory from local doctors, 405 (81%) had a normal haemoglobin. Full blood counts on these samples showed 15% with one or more blood count parameters outside 2SD of normal reference values, including increased MCV, low MCV with low MCH and MCHC, leucocytosis with neutrophilia, a few cases with neutropenia, lymphopenia, monocytosis or eosinophilia. When the limits were set at 3SD, these abnormalities were found in only 7.6% of the cases. Calculation of test utility gave a positive predictive value of 0.83, a negative predictive value of 0.85, with a likelihood ratio of 14.3 and an overall diagnostic reliability of 84%. It was concluded that haemoglobin alone is a valuable primary screening test and a full blood count is required only when anaemia is present or when the patient's history and clinical signs indicate the need for such further investigation. Using this protocol it is unlikely that any serious error will be made in diagnosing a clinically significant condition; the main limitation is failure to diagnose pre-anaemic iron deficiency.