A systematic review 1 including 11 studies with a total of 17 324 subjects was abstracted in DARE. All of the studies were performed in developing countries (most in Africa) among children aged less than 6 years. Pooled estimates of all diagnostic indices (sensitivity, specificity, likelihood ratios, LRs) varied according to the haemoglobin threshold investigated, but did not show a consistent pattern of increasing or decreasing as the threshold increased or decreased. There was also no consistency in the clinical sign (conjunctival, palmar or conjunctival pallor) found to be most accurate. In general, estimates of pooled sensitivity were fairly poor while estimates of specificity were higher. Pooled estimates of sensitivity ranged from 29.2 to 80.9% and estimates of pooled specificity varied from 67.7 to 90.8%.
Palmar pallor was modestly superior at haemoglobin less than 11 g/dL and nailbed was slightly superior at all other haemoglobin thresholds; pooled diagnostic odds ratio (DOR) at haemoglobin <11 g/dL was 4.3 (95% CI 2.6-7.2) for palmar pallor, 3.7 (2.3-5.9) for conjunctival pallor, and 3.4 (1.8-6.3) for nailbed pallor. DOR's and LR's were slightly better for nailbed pallor at all other haemoglobin thresholds.
Comment: The quality of evidence is downgraded by limitations in the review quality (incomplete reporting of review methods and inadequate reporting of study validity) and by indirectness (most of the studies were conducted in Africa).
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