Inaccuracies in Bone Densitometry for T-score Values (Comparative Study)

Overview

The authors examined 56 postmenopausal women aged 43 to 68 years and 28 men aged 40 to 66 yearssuffering from osteopenia or osteoporosis, according to the WHO classification. In every patient thefollowing measurements were made: A) T-score for: 1) the index of stiffness (S) of the left heel, USM,2) the bone mineral density of the left heel (BMDp), DEXA (g Ca hydroxyapatite/cm2), 3) the bonemineral density of the trabecular vertebral bone L1 (BMDL 1), QCT (mg Ca hydroxyapatite/cm3), B)Z-score for 1) S of the left heel bone, USM (index) 2) BMDp of the left heel bone, DEXA (g Cahydroxyapatite/cm 2 only in the group of women, for men the apparatus did not give values of theZ-score, 3) BMDL 1 of the trabecular bone of the vertebra L1 QCT (mg Ca hydroxyapatite/cm2.Objective: To determine the character of the distribution of values of T-score and Z-score for theselected measurements and compare them using statistical analysis. Statistical analysis: Thedifferences among the assessed values of T-score (Z-score) were evaluated by the parametric ornon-parametric method of determining of 95% confidence intervals (CI). Results: The differencesbetween values of the Z-score and between the T-score were statistically significant, whereby thedifferences were lower in values of Z-score in both groups. Conclusion: The greatest differencesbetween 95% CI characterizing individual measurements of T-score values (as compared withZ-score) were found in those densitometers whose ageefined reference groups of young adultsdiffered most and conversely, the smallest differences were found between age-defined referencegroups. In the higher variation of values of the T-score and Z-score participates the non-standardselection of a reference group of young adults for densitometers QCT, PIXI, Achilles plus used inthe study. The age characteristic of a reference group for the T-score should be a standard one forall types of densitometers.

Key words:
bone densitometric methods, T-score, Z-score, diagnostics of osteoporosis