The numerical differences in the composition of both groups between baseline and 18 months were due to deaths: 13 patients on dialysis and two in the general group, resulting in totals of 67 patients in the CHP versus 58 in the GPP group. The demographic characteristics of both groups are presented in .
The demographic characteristic of studied patients
The average femur neck bone mass loss in the GPP group was 0.056 g/cm2 during the investigated period of 18 months, or 3.11 mg/cm2 per month. Loss of bone mass in the CHP group for the same localization and period was 0.092 g/cm2, or 5.11 mg/cm2 per month. The average lumbar spine bone mass loss in the GPP group was 0.012 g/cm2 over the 18-month period, or 0.66 mg/cm2 per month; whereas the bone mass loss in the CHP group for the same localization and period was 0.016 g/cm2, or 0.89 mg/cm2 per month.
Absolute BMD values, T-scores, and Z-scores obtained by DEXA for the GPP and CHP groups at both time points are presented in and .
Figure 1 General population patient absolute bone mineral density (BMD) values, T-scores, and Z-scores obtained dual energy X-ray absorptiometry data in both scanned periods. Values are presented as mean ± SD or range (highest and lowest value). F, femur; (more ...)
Figure 2 Chronic hemodialysis patient absolute bone mineral density (BMD) values, T-scores, and Z-scores obtained dual energy X-ray absorptiometry data in both canned periods. Values are presented as mean ± SD or range (highest and lowest value). F, femur; (more ...)
The mean femoral neck and lumbar spine BMDs were 0.900 ± 0.14 g/cm2 at baseline and 0.866 ± 0.14 g/cm2 after 18 months in the GPP group, and 0.823 ± 0.16 g/cm2 at baseline and 0.769 ± 0.13 g/cm2 after 18 months in the CHP group. The two-tailed p value (between femoral neck BMD at baseline and after 18 months) was 0.0577 for the GPP group and 0.0002 for the CHP group; whereas that between lumbar spine BMD at baseline and after 18 months was 0.6820 for the GPP group, and 0.5389 for the CHP group.
At baseline, there were 12 CHP subjects with osteoporosis (T-score < -2.5); this number increased to 20 after 18 months. The correlation between BMI and BMD was; r = -0.36 (p = 0.005). The mean BMD of males (after matching by hemodialysis duration, 2 to 10 years) was 0.804 ± 0.14 g/cm2, whereas that of females was 0.675 ± 0.085 g/cm2.
Comparisons of hip and lumbar spine BMD between the GPP and CHP groups (f test for equal variances, statistical t test, and coefficient of two-tailed probability p) are presented in .
A t test for unpaired data between general population patient (GPP) and chronic hemodialysis patient (CHP) groups. BMD, bone mineral density; BL, base line; LS, lumbar spine; eq. var., eqyal variances; prob., probability.
Within the CHP group, the hip BMD between baseline and 18 months showed a p < 0.001 and f = 32.99 (Greenhouse-Geisser, G-G); the lumbar spine BMD between baseline and 18 months showed a p < 0.9797 and f = 0.00065 (G-G). Among the GPP group, the hip BMD results between baseline and 18 months showed a p < 0.001 and f = 32.12 (G-G), while those of the lumbar spine BMD were p < 0.240 and f = 1.41 (G-G).
Levels of laboratory markers involved in bone metabolism (albumin, C-reactive protein, calcium, ionized calcium, alkaline phosphatase, and PTH) are presented in . The values are listed separately for the CHP and GPP groups at baseline and after 18 months. The correlation of each parameter with lumbar spine BMD is presented as simple linear regression indexes r and p.
Correlation between laboratory markers and lumbar spine bone mineral density in chronic hemodialysis patient (CHP) and general population (GP) group