Agreement between dried blood spots and HemoCue in Tamil Nadu, India

India retains the world's largest burden of anemia despite decades of economic growth and anemia prevention programming. Accurate screening and estimates of anemia prevalence are critical for successful anemia control. Evidence is mixed on the performance of HemoCue, a point-of-care testing device most widely used for large-scale surveys. The use of dried blood spots (DBS) to assess hemoglobin (Hb) concentration is a potential alternative, particularly in field settings. The objective of this study is to assess Hb measurement agreement between capillary HemoCue and DBS among two age groups, children 6-59 months and females age 12-40 years. We analyzed data from the baseline round of a cluster randomized rice fortification intervention in Cuddalore district of Tamil Nadu, India. Capillary blood was collected from a subset of participants for Hb assessment by HemoCue 301 and DBS methods. We calculated Lin's concordance correlation coefficient, and tested bias by conducting paired t-tests of Hb concentration. Independence of the bias and Hb magnitude was examined visually using Bland-Altman plots and statistically tested by Pearson's correlation. We assessed differences in anemia classification using McNemar's test of marginal homogeneity. Concordance between HemoCue and DBS Hb measures was moderate for both children 6-59 months (ρ_c = 0.67; 95% CI 0.65, 0.71) and females 12-40 years (ρ_c = 0.67: 95% CI 0.64, 0.69). HemoCue measures were on average 0.06 g/dL higher than DBS for children (95% CI 0.002, 0.12; p = 0.043) and 0.29 g/dL lower than DBS for females (95% CI - 0.34, - 0.23; p < 0.0001). 50% and 56% of children were classified as anemic according to HemoCue and DBS, respectively (p < 0.0001). 55% and 47% of females were classified as anemic according to HemoCue and DBS, respectively (p < 0.0001). There is moderate statistical agreement of Hb concentration between HemoCue and DBS for both age groups. The choice of Hb assessment method has important implications for individual anemia diagnosis and population prevalence estimates. Further research is required to understand factors that influence the accuracy and reliability of DBS as a methodology for Hb assessment.