Haemoglobin colour scale for anaemia diagnosis where there is no laboratory: a systematic review

Background Anaemia is a major public health problem, in poor countries most of the cases are diagnosed clinically. This is inaccurate and the haemoglobin colour scale (HCS) has been developed as an inexpensive, simple alternative for assessing anaemia. Laboratory and community studies have assessed its diagnostic accuracy, but controversy over its validity and usefulness remains. We carried out a systematic review to identify and summarize studies, explain heterogeneity, and make recommendations for future research.

Methods We searched electronic databases (MEDLINE, EMBASE, CINAHL, and Science Citation Index), checked documents and references, and contacted experts. We included all the studies comparing HCS diagnostic accuracy with a reference standard. Both reviewers independently screened titles and abstracts, assessed studies for inclusion, appraised quality, and extracted data.

Results We included 14 studies, mostly from sub-Saharan Africa. Studies had heterogeneous populations, health care settings, anaemia prevalence, and findings. HCS sensitivity for detecting anaemia was high in most of the studies (75-97%); specificity was generally lower (41-98%). Sensitivity and specificity were higher for laboratory-based studies compared with more pragmatic 'real-life' studies, and the 'study setting' appeared to explain some of the heterogeneity. Five studies compared the HCS with clinical diagnosis; sensitivity was higher for the HCS in four studies, but specificity was often higher with clinical diagnosis. A few studies evaluated the HCS in situations where there was no laboratory.

Conclusions The HCS may improve anaemia diagnosis where there is no laboratory, but there is a need for policy-relevant diagnostic research which is pragmatic, implementation-focused and assesses clinical outcomes. This requires a different approach and research skill-mix from efficacy studies.