Clinical use of WHO haemoglobin colour scale: validation and critique

Abstract

Aim—The World Health Organisation (WHO) haemoglobin colour scale has been developed as a simple, inexpensive clinical device for diagnosing anaemia when laboratory based haemoglobinometry is not available. In an initial validation study at several health centres, scale readings were compared with measurements of haemoglobin by the laboratory. This showed the scale to have 90% sensitivity and 70% specificity in identifying whether anaemia was present or not. In addition, when present, the degree of anaemia was correctly classified in clinical terms as moderate, pronounced, or severe, with an overall sensitivity of 60% and specificity of 88%. Errors were mainly marginal—that is, between two adjacent categories—but there were also some major discrepancies, such as a blood with a haemoglobin of 6–7 g/dl being read as normal or vice versa. Because this would compromise the scale's reliability in practice, this study was undertaken to identify the causes of the discrepancies and to reassess the performance of the scale.