Hemoglobin Thresholds for Defining Anemia among Healthy Infants Aged 0-5 Months in China: A Population-based Study.

Objective: To develop hemoglobin (Hb) percentiles and thresholds for defining anemia among infants aged 0-5 months in China. Methods: 17 years in China, a nationwide cross-sectional study, was conducted between 2019 and 2021. Hb levels were measured in infants using the HemoCue 201+ analyzer. Age- and sex-specific Hb distributions were constructed for "healthy infants", defined as those with adequate iron reserves at birth, exclusive breastfeeding, normal weight-for-age Z-score and weight growth velocity, normal neuropsychological development, and absence of acute or chronic diseases. A generalized additive model for location, scale, and shape was applied to fit the Hb percentiles. The 5th percentile of the Hb distribution was defined as the threshold for anemia. Results: A total of 10,174 infants aged 0-5 months participated in the study, among whom 2,155 healthy infants were included in the analysis. Hb levels peaked at birth, gradually decreased to a nadir around 60 days after birth, and then rose to a plateau. The Hb thresholds defining anemia were 102.7 g/L, 96.3 g/L, 92.8 g/L, 95.4 g/L, 97.1 g/L, and 95.8 g/L for the 0-, 1-, 2-, 3-, 4-, and 5-month age groups, respectively. Conclusion: This study establishes hemoglobin thresholds for defining anemia in infants aged 0-5 months based on a nationwide, population-based dataset in China.