Is It Useful And Practical To Assess Body Fat In Sick Infants Using Skinfolds?
Authors: Wright Charlotte M , Milani Shamsi Afiat , Gerasimidis Konstantinos 
Published: November 2023

Sick infants have increased risk of undernutrition, but often also have unusual body proportions, making anthropometry unreliable in detecting low fat stores. Thus body composition (BC) assessment methods may be needed to identify undernutrition reliably. BC methods are often costly, impractical for clinical use and tend not to have reference data for infants. Skinfolds (SF) are cheap and portable and well established in adults, but little used in infants. The WHO growth chart project published standards for subscapular (SS) and triceps (TC) skinfolds from age 3 months to 5 years in 2007. We aimed to assess the practicality of measuring SF in hospitalised infants and the relative predictive validity of different references and thresholds to detect nutritional risk, in two settings with different prevalence of undernutrition.

Methods

As part of a study of nutritional screening project (iNEWS) infants were studied at admission to two tertiary children's hospitals in Glasgow, UK (aged 0–12 months) and Tabriz, Iran (1–12 months). Oversampling was used to recruit infants likely to be at higher risk of undernutrition. Four researchers recruited in the UK and one in Iran. Paediatric Subjective Global Nutritional Assessment (SGNA) was undertaken to determine malnutrition risk and TC and SS skinfolds were measured using Holtain calipers. Measurements were converted into Z scores relative to the WHO 2006 standard. The WHO SF standard only starts at 3 months, so a reference for sum of skinfolds (SSF) for ages 0–12 months was modeled from the UK cohort SF data, using the LMS method. As the lower limit for SF in the UK cohort showed little variation up to age 12 months, we also used a SSF 5th centile threshold of 10mm.

Results

In the UK 195 infants and in Iran 179 were measured at mean (SD) age 4.8 (3.4) and 5.4 (2.9) months. Measuring SF proved practical and acceptable. In Iran 30% infants were at high SGNA nutritional risk, compared to 14% in UK. WHO z scores could be calculated for 236 infants age 3m+, while 369 had iPYMS z scores and SSF. Mean SF z scores varied strongly with nutrition risk in Iran, but only weakly in the UK; only one UK high nutrition risk infant actually had low fat stores (Table). In Iran SSF <10mm had a 67% sensitivity for high nutrition risk and specificity of 89% with a positive predictive value of 72%.

Conclusions

The iPYMS reference gave similar results to WHO, but so did a raw sum of skinfolds threshold of 10mm, suggesting that this could be used clinically as a simple threshold for undernutrition in children aged under one year. Measuring skinfolds might be more reliable than conventional screening to identify truly malnourished children in countries with a low background prevalence of undernutrition.

Support or Funding Information

Data collection in the UK was part funded by Organix Foundation

SF z scores and proportion with low SF, using different analytical methods, broken down by country and malnutrition risk

SGNA
UK
Iran

Mean(SD)
Low
High
p*
Low
High
p*

SF z score (WHO)
0.33 (1.1)
−0.95 (1.0)
0.008
−0.85 (1.0)
−3.00 (1.1)
<0.001

SSF z score (UK)
0.23 (0.9)
−0.76 (0.8)
<0.001
−0.78 (0.8)
−2.46 (0.7)
<0.001

Mean SF <‐2z (WHO)
33% (2)
17% (1)
0.049
5.6% (3)
61% (33)
<0.001

SSFz <‐2 (UK)
40% (2)
20% (1)
0.190
3.8% (2)
73% (38)
<0.001

SSF <10mm
29% (2)
14% (1)
0.072
8.0% (4)
72% (36)
<0.001

χ2

ANOVA