Interpretation of World Health Organization growth charts for assessing infant malnutrition: a randomised controlled trial

Aims: The study aims to assess the effects of switching from National Center for Health Statistics (NCHS) growth references to World Health Organization (WHO) growth standards on health-care workers' decisions about malnutrition in infants aged <6 months.

Methods: We conducted a single blind randomised crossover trial involving 78 health-care workers (doctors, clinical officers, health service assistants) in Southern Malawi. Participants were offered hypothetical clinical scenarios with the same infant plotted on NCHS-based weight-for-age charts and again on WHO-based charts. Additional scenarios compared growth charts with a single final weight against charts with the same final weight plus a preceding growth trend. Reported (i) level of concern, (ii) referral suggestions and (iii) feeding advice were elicited with a questionnaire.

Results: Even after adjusting for health-care worker type and experience, using WHO rather than NCHS charts increased: (i) concern: aOR 4.4 (95% CI 2.4-8.1); (ii) odds of referral: aOR 5.1 (95% CI 2.4-10.8); and (iii) odds of feeding advice which would interrupt exclusive breastfeeding (aOR 2.4, 95% CI 1.2-4.9). A preceding steady growth trend line did not affect concern, referral or feeding advice.

Conclusions: Health-care workers take insufficient account of linear growth trend, clinical and feeding status when interpreting a low weight-for-age plot. Because more infants <6 months fall below low centile lines on WHO growth charts, their use may increase inappropriate referrals and risks undermining already low rates of exclusive breastfeeding. To avoid their being misinterpreted in this way, WHO charts need accompanying guidelines and training materials that recognise and address this possible adverse effect.