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Diagnostic criteria for severe acute malnutrition among infants aged under 6 mo
Martha Mwangome1,2, Moses Ngari3,2, Greg Fegan3,4
1Kenya Medical Research Institute (KEMRI)/Wellcome Trust Research Program, Kilifi, Kenya; mmwangome@kemri-wellcome.org.
Insights
Mid-upper arm circumference (MUAC) and weight-for-age z score (WAZ) better predict mortality in infants under 6 months (U6M) than weight-for-length z scores (WLZs). These indicators can help identify high-risk infants for timely interventions.
Area of Science:
- Pediatrics
- Global Health
- Nutritional Epidemiology
Background:
- Malnutrition is a significant concern in infants under 6 months (U6M).
- Current diagnostic criteria using weight-for-length z scores (WLZs) have limitations, excluding shorter infants.
- Mid-upper arm circumference (MUAC) shows promise as a better mortality predictor in older children.
Purpose of the Study:
- To evaluate the association between anthropometric indexes and mortality risk in hospitalized U6M infants.
- To compare the predictive accuracy of WLZ, MUAC, and weight-for-age z score (WAZ) for inpatient and postdischarge mortality.
- To assess diagnostic thresholds for anthropometric measures against mortality risk in U6M infants.
Main Methods:
- Analysis of a cohort of 2882 U6M infants admitted to Kilifi County Hospital, Kenya (2007-2013).
- Primary outcomes: inpatient death and 1-year postdischarge mortality.
- Calculation of adjusted risk ratios (RRs) and hazard ratios (HRs); assessment using receiver operating characteristic (ROC) curves.
Main Results:
- MUAC and WAZ demonstrated superior prediction of both inpatient and postdischarge mortality compared to WLZ (P < 0.0001).
- A single MUAC threshold of <11.0 cm was as effective as age-varying thresholds and outperformed WLZ <-3.
- Small size at birth did not mitigate the mortality risk associated with anthropometric indexes.
Conclusions:
- MUAC and WAZ are effective indicators for identifying U6M infants at highest risk of mortality.
- These findings suggest a need to re-evaluate current diagnostic criteria for malnutrition in U6M infants.
- Further research is warranted to develop and test interventions for high-risk U6M infants identified by MUAC or WAZ.
Abstract:
Background: There is an increasing recognition of malnutrition among infants under 6 mo of age (U6M). Current diagnosis criteria use weight-for-length z scores (WLZs), but the 2006 WHO standards exclude infants shorter than 45 cm. In older children, midupper arm circumference (MUAC) predicts mortality better than does WLZ. Outcomes may also be influenced by exposure to HIV and size or gestational age at birth. Diagnostic thresholds for WLZ, MUAC, and other indexes have not been fully evaluated against mortality risk among U6M infants.Objective: The aim was to determine the association of anthropometric indexes with risks of inpatient and postdischarge mortality among U6M infants recruited at the time of hospitalization.Design: We analyzed data from a cohort of U6M infants admitted to Kilifi County Hospital (2007-2013), Kenya. The primary outcomes were inpatient death and death during follow-up over 1 y after discharge. We calculated adjusted RRs for inpatient mortality and HRs for postdischarge mortality for different anthropometric measures and thresholds. Discriminatory value was assessed by using receiver operating characteristic curves.Results: A total of 2882 infants were admitted: 140 (4.9%) died in the hospital and 1405 infants were followed up after discharge. Of these, 75 (5.3%) died within 1 y during 1318 child-years of observation. MUAC and weight-for-age z score (WAZ) predicted inpatient and postdischarge mortality better than did WLZ (P < 0.0001). A single MUAC threshold of <11.0 cm performed similarly to MUAC thresholds that varied with age (all P > 0.05) and performed better than WLZ <-3 for both inpatient and postdischarge mortality (both P < 0.001). Reported small size at birth did not reduce the risk of death associated with anthropometric indexes.Conclusions: U6M infants at the highest risk of death are best targeted by using MUAC or WAZ. Further research into the effectiveness of potential interventions is required.