Background The accurate measurement of body composition is useful in assessments of preterm infant growth and nutritional status.

Objective To evaluate the accuracy of a pediatric air-displacement plethysmograph (ADP) system (PEA POD Infant Body Composition System, Life Measurement, Inc., Concord, CA, USA) for determining percentage body fat (%BF) in a preterm infant population.

Design/Methods Preterm infants (n = 10), gestational age = 30–36 (min–max) weeks (32.50 + 1.96, Mean + SD), age tested = 0.85–4.0 weeks, (2.20 + 1.34), weight = 1.48–2.10 Kg (1.83 + 0.21) were examined by ADP. Reference %BF values were determined using total body water (TBW) measurements.

Results Mean %BF by ADP was 5.67 + 1.84 and mean % BF by TBW was 5.99 + 2.56. Mean difference in %BF between the two methods was −0.32 + −1.57. Regression analysis showed that %BF by ADP was significantly associated with %BF by TBW (R2 = 0.63, SEE = 1.65, P = 0.006). There was a significant correlation between %BF results obtained by the two methods (r = 0.79). Bland-Altman analysis was performed to assess potential bias. No bias was found (r = −0.48, P = 0.16) and 95% limits of agreement were −3.40 to 2.76%BF.

Conclusion When compared to the TBW model, this initial study has shown that this ADP System provides an accurate assessment of %BF in preterm infants. Overall agreement between the two methods is good with individual variations in %BF consistent with previous findings. A larger study comparing TBW to ADP in preterm infants is currently underway.