Haemoglobin concentration thresholds that discriminate functional outcomes among children aged 6–30 months in eight countries: a pooled analysis of individual participant data

Abstract

Introduction: The WHO cut-offs to define anaemia among children (haemoglobin, Hb <105 g/L in 6–23 months and <110 g/L in 24–59 months) are based on the distribution of Hb concentrations in a healthy population. Our objective was to identify Hb values that best discriminate functional outcomes among children aged 6–30 months. Methods: We used previously compiled datasets from an individual participant data meta-analysis of effects of small quantity lipid-based nutrient supplements. Participants were eligible for this pooled analysis if they had Hb measured at 6–30 months and data on at least one functional outcome of interest, which included physical activity and sleep patterns, and language, socioemotional and motor development. We stratified the datasets by child age in 3-month intervals and analysed associations of Hb with both concurrent and subsequently measured (longitudinal) outcomes. If Hb significantly discriminated the 25th, 50th or 75th percentile of the outcome based on the pooled area under the receiver operating characteristic curve (AUC), we identified the Hb value with the highest concordance probability as the best discriminatory threshold. Results: 11 datasets from 8 countries including 27 626 children were analysed. Hb significantly discriminated 21 of 47 concurrent and 11 of 32 longitudinal Hb-outcome associations. Best Hb discriminatory thresholds ranged from 102 to 111 g/L for concurrent physical activity outcomes, 103–116 g/L for concurrent developmental outcomes, and 109–117 g/L for longitudinal developmental outcomes. The I2 for the pooled AUC analysis indicated generally low to moderate heterogeneity across studies. Conclusions: The current WHO cut-offs to define anaemia among children are in the middle to upper range of Hb values that best discriminate concurrent physical activity and development, and are in the lower range of values that best discriminate subsequent child development. Along with other types of evidence, this study provides additional evidence to inform Hb cut-offs to define anaemia among young children.