Performance of Sahli and colour scale methods in diagnosing anaemia among school children in low prevalence areas.

Our aim was to compare the performance of the Sahli and Colour Scale methods in diagnosing anaemia in school children, where the prevalence of anaemia is low and the haemoglobin level ranges from mild to moderate (8-11 g/dl). The study was conducted in February 2001, in Qena Governorate, Upper Egypt. The haemoglobin level measured by the two methods in each child were compared with the result obtained by using a portable haemoglobin photometer 'HemoCue'. A total of 149 school children were included in the study. Using HemoCue, 17.4% children were anaemic; using the Sahli method (SM), 66.4% children were anaemic; and using the Haemoglobin Colour Scale (HCS) method, 57.7% children were anaemic. Neither method detected any cases of severe anaemia (Hb < 7 g/dl). Both the Sahli and Colour Scale methods are sensitive but have low specificity, giving a high rate of false positive results. Both methods perform perform very similarly in haemoglobin measurement; they fulfil many of the criteria for their use at primary health care level and detect almost all cases of anaemia in a given population, even if the level of anaemia is mild. Standards for collection, handling and disposal of blood samples are guaranteed more easily by the HCS than the SM. Moreover, lay people can easily manage the HCS with success after brief training. We suggest to gradually replace the SM by the HCS method in primary health care (PHC) centres. Where anaemia levels are moderate to mild, the use of SM and HCS as tools to define anaemia prevalence might be limited, as they often label healthy individuals as anaemic. Both methods remain a useful diagnostic tool to confirm the diagnosis of clinically suspected anaemia in areas where the prevalence of anaemia is low and the haemoglobin level ranges from mild to moderate.