Reliability tests and guidelines for B‐mode ultrasound assessment of central adiposity

Introduction Ultrasound represents a validated and relatively inexpensive diagnostic device for assessing central adiposity; however, widespread adoption has been impeded by the lack of reliable standard operating procedures. Purpose To examine the reliability of, and describe guidelines for, ultrasound-derived recording of intra-abdominal fat thickness (IAT) and maximal preperitoneal fat thickness (PFT). Methods Ultrasound scans were obtained from 20 adults (50% female, 26 ± 7 years, 24·5 kg/m2) on three different mornings. IAT was assessed 2 cm above the umbilicus (transverse plane) measuring from linea alba to: (i) anterior aorta, (ii) posterior aorta and (iii) anterior aspect of the vertebral column. PFT was measured from linea alba to visceral peritoneum in (i) sagittal and (ii) transverse planes, immediately over and inferior to the xiphi-sternum, respectively. Results For IAT, the criterion intraclass correlation coefficient (ICC) of 0·75 was exceeded for measurements to anterior aorta (0·95), posterior aorta (0·94) and vertebra (0·96). The reliability coefficient expressed as a percentage of the mean (RC%) was lowest (better) for measurement to vertebrae (9·8%). For PFT, mean thickness was comparable for sagittal (1·74 cm) and transverse (1·76 cm) planes; ICC values were also comparable for both planes (0·98 vs. 0·98, respectively), as were RC% (7·5% vs. 7·1%, respectively). Conclusions IAT assessments to the vertebra were marginally more reliable than those to other structures. While PFT assessments were equally reliable for both measurements planes, precise probe placement was easier for the sagittal plane. Based on these findings, guidelines for the reliable measurement of central adiposity using ultrasound are presented.