VALIDATION OF ACCURACY AND PRECISION OF DUAL-ENERGY X-RAY ABSORPTIOMETRY FOR INFANTS

There is limited information on the validity of bone mineral content m easurement by dual energy X-ray absorptiometry (DXA BMC) for use in su bjects with low body mass. We evaluated the accuracy and precision of DXA in piglets (body weight 886-5526 g, median 2096 g). Stepwise multi ple regression analyses showed that ash weight is the major determinan t of DXA BMC (adjusted r(2) = 0.98, RMS residual = 3.61 g). The interc ept was not significantly different from zero. DXA BMC measurements of other piglets under various clinical situations showed no significant effect from the use of cotton blanket, diaper, or positioning (prone, supine, lateral). In vivo replication of DXA BMC measurements of infa nts at a postnatal age of from 1-350 days showed a slope of 0.99 and h igh correlation coefficient (r(2) = 0.99, RMS residual = 3.59 g). The intercept was not significantly different from zero, and the average c oefficient of variation of duplicate DXA BMC in infants was 2.8%. We c onclude that DXA BMC reliably but proportionately underestimates ash w eight and is a highly precise method for measuring bone mineral status in young pediatric subjects.