Bone Abstracts

Objective: The objective of this study was to enable migration of DXA data of patients following replacement of the GE Lunar DPX-Pro, pencil beam densitometer with GE Lunar iDXA, fan beam densitometer.

Methods: Scans of total body were conducted for 67 subjects, aged 3.0 to 19.9 years, on both machines. A sub-set of six subjects (3 boys) were randomly selected and reserved as a validation sample. Differences between the values obtained on the two machines were tested using the Student’s T-Test. Regression Analyses were applied to the data of the remaining 61 subjects (33 boys) to obtain regression equations for predicting DPX values of Total Body Less Head (TBLH) Bone Mineral Content (BMC) and TBLH Bone Area (BA) using corresponding iDXA values for both genders. Values were log transformed before generating regression equations.

Results: Regression equations for TBLH BMC and TBLH BA were generated with DPX measurements as the dependent variable and iDXA as the predicting variable. These equations have been represented in the following figures: Figure 1a and 1b log transformed values of TBLH BMC of DPX against iDXA for males and females respectively; Figure 2a and 2b log transformed values of TBLH BA of DPX against iDXA for males and females respectively. The observed DPX values and predicted values were similar (P>0.1). The TBLH BMC and TBLH BA z-scores were calculated for both values. The z-scores were tested on the validation sample and it was found that the bone status as defined by z-score remained similar after the use of predicted BMC values.

Conclusions: In the absence of reference data for the iDXA, the z-scores from the predicted TBLH BMC and TBLH BA may be used to assess Indian children’s bone status.

Disclosure: The authors declared no competing interests.

Figure 1

Figure 2