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Table 2 Prevalence of reduced BMD measured by dual-energy x-ray absorptiometry at different skeletal sites.

From: Osteoporosis in ankylosing spondylitis - prevalence, risk factors and methods of assessment

Measurement site Age-group,
years
BMD,
mean ± SD
T-score,
mean ± SD
Z-score,
mean ± SD
Patients with osteoporosis/BMD below expected range for age, number (%)a Patients with osteopenia,
number (%)
Patients with
normal BMD
number (%)
Women        
AP lumbar spine < 50 1.014 ± 0.134 -0.30 ± 1.22 0.02 ± 1.25 2 (5) 0 (0) 41 (95)
  ≥ 50 0.899 ± 0.150 -1.35 ± 1.37 0.14 ± 1.38 12 (27) 15 (34) 17 (39)
Lat lumbar spine < 50 0.741 ± 0.102 -0.94 ± 1.22 -0.25 ± 1.26 3 (7) 0 (0) 40 (93)
  ≥ 50 0.616 ± 0.114 -2.43 ± 1.36 -0.05 ± 1.42 20 (45) 15 (34) 9 (20)
Total hip < 50 0.925 ± 0.122 -0.13 ± 1.00 0.07 ± 0.99 0 (0) 0 (0) 43 (100)
  ≥ 50 0.832 ± 0.108 -0.89 ± 0.88 0.10 ± 0.85 0 (0) 20 (46) 23 (54)
Femoral neck < 50 0.804 ± 0.127 -0.41 ± 1.15 -0.06 ± 1.13 0(0) 0 (0) 43 (100)
  ≥ 50 0.702 ± 0.103 -1.32 ± 0.93 -0.01 ± 0.91 4 (9) 24 (56) 15 (35)
Total radius < 50 0.576 ± 0.038 -0.05 ± 0.70 0.32 ± 0.74 0(0) 0 (0) 43 (100)
  ≥ 50 0.517 ± 0.065 -1.14 ± 1.21 0.18 ± 1.09 7 (16) 17 (39) 20 (45)
Men
AP lumbar spine < 50 1.057 ± 0.154 -0.31 ± 1.41 -0.18 ± 1.41 3 (5) 0 (0) 57 (95)
  ≥ 50 1.092 ± 0.184 0.18 ± 1.67 0.63 ± 1.72 4 (7) 8 (14) 44 (79)
Lat lumbar spine < 50 0.782 ± 0.131    NA NA NA
  ≥ 50 0.740 ± 0.132    NA NA NA
Total hip < 50 0.999 ± 0.137 -0.23 ± 0.92 -0.05 ± 0.90 1 (2) 0 (0) 59 (98)
  ≥ 50 0.963 ± 0.136 -0.46 ± 0.90 0.00 ± 0.93 0 (0) 19 (33) 38 (67)
Femoral neck < 50 0.842 ± 0.130 -0.67 ± 0.95 -0.21 ± 0.93 1 (2) 0 (0) 59 (98)
  ≥ 50 0.773 ± 0.122 -1.16 ± 0.90 -0.21 ± 0.90 5 (9) 25 (44) 27 (47)
Total radius < 50 0.668 ± 0.050 -0.34 ± 0.93 -0.12 ± 0.91 1 (2) 0 (0) 59 (98)
  ≥ 50 0.633 ± 0.063 -1.03 ± 1.21 -0.25 ± 1.20 9 (16) 18 (33) 28 (51)
  1. Definition of reduced BMD in patients younger than 50 years, BMD below expected range for age (Z-score ≤ -2.0 SD), BMD within expected range for age (Z-score > -2.0 SD); in patients 50 years or older, World Health Organization definition of osteoporosis: T-score ≤ - 2.5 SD, osteopenia: T-score < -1 to > -2.5 SD; normal BMD, T-score ≥ -1SD. For lateral lumbar spine BMD in men there are no reference values available for calculation of T- or Z-scores. aData presented as the sum of patients younger than 50 years, with a Z-score ≤ -2.0 SD and patients 50 years or older with a T-score ≤ -2.5 SD.
  2. AP, anteroposterior; Lat, lateral; BMD, bone mineral density.