Of the 718 women evaluated, 447 underwent Q-CT and 271 underwent DXA. The mean ages of the two study groups were 61.2 years (range 50–89 yr) and 60 years (range 49–89 yr) for Q-CT and DXA respectively, with no significant difference in the age distribution of the two study cohorts (P-value > 0.05). The age distribution curves plotted for both the study groups too were similarly positively skewed curves with the majority screened by both the modalities included in 50 to 65 year age range (Figure 1). The mean and mode T-scores obtained by Q-CT and DXA were found to be –2.71, −3.8 and –1.63, −1.7 respectively. There was a highly significant difference between the T-scores obtained by Q-CT and DXA groups (P-value < 0.0001). The T-score distribution curves were plotted for both the study groups (Figure 2A, B). While the T-score distribution curve of Q-CT appeared to be a positively skewed curve, the DXA curve appeared a relatively more symmetric bell curve than the former. The regression analysis of both the groups (Figure 3A, B) showed a linear relationship between age and T-scores with the latter decreasing with advancing age. However the coefficient of determination (R 2) was low for both the groups (21.16% for Q-CT and 12.78% for DXA), indicating that such a relation cannot be strongly established in general population. Among those who were screened by Q-CT 58.16% were osteoporotic, 37.58% were osteopenic, and 4.25% were normal. The respective percentages in the DXA group were 30.63%, 49.82%, and 19.55% (Figure 4). Also, in this study there was discordance among BMD values of the sites scanned by DXA. Eighteen percent of the DXA study cohort were displaying osteoporosis in the femoral neck, but spine BMD was non-osteoporotic and 11% demonstrated osteoporosis in the spine but their femoral neck BMD was non-osteoporotic.
The age distribution curves plotted for both the study groups (Q-CT [blue dots] and DXA [orange squares]) showing similar positively skewed curves with majority of individuals in 50 to 65 years age range in both the study groups. DXA indicates dual-X-ray absorptiometry; Q-CT, quantitative computed tomography.
The bell curves plotted depicting the T-score distribution in the study groups. A, Q-CT curve; B, DXA curve. DXA indicates dual-X-ray absorptiometry; Q-CT, quantitative computed tomography.
Regression analysis: Linear relation found between age versus T-scores of (A) Q-CT and (B) DXA. DXA indicates dual-X-ray absorptiometry; Q-CT, quantitative computed tomography.
Spine. 2022;47(6):E258-E264. © 2022 Lippincott Williams & Wilkins