Abstract
(i) To assess diagnostic accuracy of mid-upper arm circumference (MUAC) for screening thinness and severe thinness in Indian adolescent girls aged 10-14 and 15-19 years compared with BMI-for-age Z-score (BAZ) <-2 and <-3 as the gold standard and (ii) to identify appropriate MUAC cut-offs for screening thinness and severe thinness in Indian girls aged 10-14 and 15-19 years. Cross-sectional, conducted October 2016-April 2017. Four tribal blocks of two eastern India states, Chhattisgarh and Odisha. Girls (n 4628) aged 10-19 years. Measurements included height, weight and MUAC to calculate BAZ. Standard diagnostic accuracy tests, receiver-operating characteristic curves and Youden index helped arrive at MUAC cut-offs at BAZ < -2 and <-3, as gold standard. Mean MUAC and BMI correlation was positive (0·78, P = 0·001 and r 2 = 0·61). Among 10-14 years, MUAC cut-off corresponding to BAZ < -2 and BAZ < -3 was ≤19·4 and ≤18·9 cm. Among 15-19 years, corresponding values were ≤21·6 and ≤20·7 cm. For both BAZ < -2 and BAZ < -3, specificity was higher in 15-19 v. 10-14 years. State-wise variations existed. MUAC cut-offs ranged from 17·7 cm (10 years) to 22·5 cm (19 years) for BAZ < -2, and from 17·0 cm (10 years) to 21·5 cm (19 years) for BAZ < -3. Single-age area under the curve range was 0·82-0·97. Study provides a case for use of year-wise and sex-wise context-specific MUAC-cut-offs for screening thinness/severe thinness in adolescents, rather than one MUAC cut-off across 10-19 years, depending on purpose and logistic constraints.
Highlights
Setting: Four tribal blocks of two eastern India states, Chhattisgarh and Odisha
Diagnostic accuracy of mid-upper arm circumference (MUAC) compared with BMI-for-age Z-score (BAZ) was assessed using sensitivity (SN), specificity (SP), negative predictive value (NPV) and positive predictive value (PPV), whose values were calculated using the proportion of true positives (TP), false positives (FP), true negatives (TN) and false negatives (FN) using a 2 × 2 table as shown below: Thin according to MUAC cut-offs generated in the paper
SN measures the percentage of true positives calculated as TP/(TP + FN); SP measures the percentage of true negatives calculated as TN/(TN + FP); NPV tells us how likely an adolescent is to not be thin if the test is negative, calculated as TN/(TN + FN); and PPV tells us how likely an adolescent is to be thin if the test is positive, calculated as TP/(TP + FP)
Summary
Descriptive statistics were generated using the statistical software package IBM SPSS Statistics version 20. MUAC cut-offs for screening thinness and severe thinness and year-wise MUAC cut-offs, as well as those for younger (10–14 years) and older (15–19 years) adolescents, were determined using BAZ < −2 and BAZ < −3, respectively, as the gold standard. Diagnostic accuracy of MUAC compared with BAZ was assessed using sensitivity (SN), specificity (SP), negative predictive value (NPV) and positive predictive value (PPV), whose values were calculated using the proportion of true positives (TP), false positives (FP), true negatives (TN) and false negatives (FN) using a 2 × 2 table as shown below: Thin according to MUAC cut-offs generated in the paper Yes No. Thin according to BAZ Yes No TP FP FN TN. Values of SN, SP, PPV and NPV were calculated for MUAC cut-offs points against BAZ < −2 and BAZ < −3
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