Short communication: Colour vision and proficiency in diagnostic microscopy

The microscopical diagnosis of infectious diseases is an essential medical laboratory service in resource-poor countries. We conducted an external quality assessment (EQA) of peripheral laboratories in southern Ethiopia using a panel of 20 ready-prepared sputum and blood smears containing either no pathogens or locally common pathogens. Microscopists also undertook a colour discrimination test (Farnsworth-Munsell 100 hue test). Twenty microscopists from 10 health centres participated. Their microscopy results were compared with that of the EQA controllers. Their Kappa indices of agreement ranged from 0.1 to 0.89 (mean +/- SD: 0.58 +/- 0.21). Kappa values were analysed according to microscopists' colour discrimination ability. The Kappa indices for the correct reading of diagnostic smears were associated with the colour vision ability of the technicians. Our results suggest that routine quality improvement activities may not achieve their desired effect if the colour discrimination abilities of technicians are not considered.