Health of children classified as underweight by CDC reference but normal by WHO standard.

OBJECTIVE: To ascertain measures of health status among 6- to 24-month-old children classified as below normal weight-for-age (underweight) by the Centers for Disease Control and Prevention (CDC) 2000 growth reference but as normal weight-for-age by the World Health Organization (WHO) 2006 standard. METHODS: Data were gathered from children and primary caregivers at emergency departments and primary care clinics in 7 US cities. Outcome measures included caregiver rating of child health, parental evaluation of developmental status, history of hospitalizations, and admission to hospital at the time of visit. Children were classified as (1) not underweight by either CDC 2000 or WHO 2006 criteria, (2) underweight by CDC 2000 but not by WHO 2006 criteria, or (3) underweight by both criteria. Associations between these categories and health outcome measures were assessed by using multiple logistic regression analysis. RESULTS: Data were available for 18 420 children. For each health outcome measure, children classified as underweight by CDC 2000 but normal by WHO 2006 had higher adjusted odds ratios (aORs) of adverse health outcomes than children not classified as underweight by either; children classified as underweight by both had the highest aORs of adverse outcomes. For example, compared with children not underweight by either criteria, the aORs for fair/poor health rating were 2.54 (95% confidence interval: 2.20-2.93) among children underweight by CDC but not WHO and 3.76 (3.13-4.51) among children underweight by both. CONCLUSIONS: Children who are reclassified from underweight to normal weight in changing from CDC 2000 to WHO 2006 growth charts may still be affected by morbidities associated with underweight.