Agreement Between Venous and Capillary Haemoglobin Concentrations in a High-Burden Urban Indian Setting: A...

Background: Anaemia is a major public health issue in India, where point-of-care testing is central to national control strategies. This study evaluated the diagnostic accuracy of the HemoCue^® Hb 201⁺ for haemoglobin (Hb) estimation from capillary blood compared to the gold-standard venous blood analysis. Methods: In a cross-sectional study of 748 participants in a low-resource urban Delhi setting, Hb levels from single-drop capillary samples (HemoCue^® Hb 201⁺) were compared to those from venous samples (automated autoanalyzer). Agreement was assessed using Bland-Altman analysis, Passing-Bablok regression, and standard diagnostic accuracy metrics. Results: The mean (SD) haemoglobin concentration was lower in capillary samples (11.83 [1.95] g/dL) than in venous samples (12.56 [1.89] g/dL). Capillary Hb was, on average, 0.73 g/dL lower than venous Hb (95% limits of agreement: -3.11 to 1.65 g/dL). Consequently, the HemoCue^® Hb 201⁺ significantly overestimated anaemia prevalence (54.4% vs. 35.0%). The capillary method demonstrated high sensitivity (92.4%) for detecting anaemia but only moderate specificity (66.1%), indicating a tendency for false positives. Conclusions: Although the HemoCue^® Hb 201⁺ is a sensitive tool for anaemia screening in field settings, the moderate specificity and the significant negative bias can lead to overestimation of prevalence and potential misclassification of individuals. However, the limitation of single-drop capillary sampling warrant cautious interpretation of results, particularly for clinical decision-making and precise prevalence estimation.