Point-of-care haemoglobin measurement in pooled capillary blood by a portable autoanalyser: comparison with venous blood haemoglobin measured by reference methods in cross-sectional and longitudinal studies.

Population-based surveys commonly use point-of-care (POC) methods with capillary blood samples for estimating haemoglobin (Hb) concentrations; these estimates need to be validated by comparison with reference methods using venous blood. In a cross-sectional study in 748 participants (17-86y, 708 women, Hb: 5.1 to 18.2 g/dL) from Hyderabad, India, we validated Hb measured from a pooled capillary blood sample by a POC autoanalyser (Horiba ABX Micros 60OT, Hb-C-AA) by comparison with venous blood Hb measured by two reference methods: POC autoanalyser (Hb-V-AA) and cyanmethemoglobin method (Hb-V-CM). These comparisons also allowed estimation of blood sample related and equipment related differences in the Hb estimates. We also conducted a longitudinal study in 426 participants (17-21y) to measure differences in the Hb response to iron folate treatment by the capillary blood POC method compared to the reference methods. In the cross-sectional study, Bland Altman analyses showed trivial differences between source of blood (Hb-C-AA and Hb-V-AA; mean difference, limits of agreement: 0.1, -0.8 to 1.0 g/dL) and between analytical methods (Hb-V-AA and Hb-V-CM; mean difference, limits of agreement :< 0.1, -1.8 to 1.8 g/dL). Cross-sectional anaemia prevalence estimated using Hb-C-AA did not differ significantly from Hb-V-CM or Hb-V-AA. In the longitudinal study, the Hb increment in response to IFA intervention was not different when using Hb-C-AA (1.6 ± 1.7 g/dL) compared to Hb-V-AA (1.7± 1.7g/dL) and Hb-V-CM (1.7± 1.7 g/dL). The pooled capillary blood-autoanalyzer method (Hb-C-AA) offers a practical and accurate way forward for POC screening of anaemia.