Table 3.

Factors Related to Bone Z-Score Outcome Variables. Multivariate linear regression models in Subjects with Thalassemia and Healthy Controls (n=59)

Outcome	Predictor Variable	Coefficient	Standard Error	p-value	Adjusted r2
Spine aBMD Z-score	Thalassemia diagnosis	−1.79	0.31	<0.001	0.62
	Male gender	0.47	0.24	0.057
	Height Z-score	0.23	0.10	0.028
Whole Body BMC Z-score	Thalassemia diagnosis	−0.76	0.35	0.034	0.75
	Height Z-score	0.59	0.1	<0.001
	Lean Mass Index Z-score	0.39	0.16	0.019
Cortical BMC Z-score	Thalassemia diagnosis	−0.85	0.26	0.002	0.74
	Tibial Length Z-score	0.47	0.07	<0.001
	Lean mass index Z-score	0.72	0.14	<0.001
Cortical Area Z-score	Thalassemia diagnosis	−1.10	0.25	<0.001	0.74
	Tibial Length Z-score	0.47	0.08	<0.001
	Lean mass index Z-score	0.64	0.14	<0.001
Cortical Thickness Z-score	Thalassemia diagnosis	−1.3	0.28	<0.001	0.69
	Tibial Length Z-score	0.66	0.10	<0.001
	Tibial Muscle Z-score	0.40	0.12	0.003
Periosteal Circumference Z-score	Tibial Length Z-score	0.72	0.08	<0.001	0.59
	Tibial Muscle Z-score	0.59	0.10	<0.001
Section Modulus Z-score	Tibial Length Z-score	0.82	0.08	<0.001	0.66
	Tibial Muscle Z-score	0.66	0.09	<0.001

Summary of multivariate linear regression models: endosteal circumference, cortical vBMD and trabecular vBMD Z-scores were not included as outcomes in this table given they were not significantly different between Thal and control in the univariate analyses (Table 2). Predictor variables above were included if univariate relationship existed to any outcome variable of p<0.1, these variables included thalassemia diagnosis, gender (male=reference), age, tanner stage (pre-pubertal=reference), height for age Z-score, lean mass index Z-score, tibial muscle mass Z-score determined at the 66% site, kilocalories as %dietary reference index, calcium intake as a %DRI and serum vitamin D (ng/mL). Only those predictor variables that were significant in each individual multivariate model are included above with the individual coefficients and p-values for the predictor variables, and r² for the models adjusted for sample size. For example, as predicted in the model above, Whole body BMC Z-score is expected to increase by 0.59 units for every 1 SD increase in height Z-score in the subjects studied.