Osteoporosis in ankylosing spondylitis - prevalence, risk factors and methods of assessment
Arthritis Research & Therapy, 05/10/2012
Klingberg E et al. – Osteoporosis and osteopenia is common in ankylosing spondylitis (AS) and associated with high disease burden. Lateral and volumetric lumbar dual energy x–ray absorptiometry (DXA) are more sensitive than anteroposterior (AP) DXA in detecting osteoporosis and are less affected by syndesmophyte formation.
Methods of assessment were questionnaires, back mobility tests, blood samples, lateral spine radiographs for syndesmophyte grading (mSASSS), DXA of hip, radius and of lumbar spine in anteroposterior (AP) and lateral projections with estimation of volumetric BMD (vBMD).
AS patients (modified New York criteria), 87 women and 117 men, mean age 50+/–13 and disease duration 15+/–11 years were included.
According to World Health Organization (WHO) criteria 21% osteoporosis and 44% osteopenia was diagnosed in patients >=50 years.
Under age 50 BMD below expected range for age was found in 5%.
Interestingly lateral lumbar DXA showed significantly lower BMD and revealed significantly more cases with osteoporosis as compared with AP DXA.
Lumbar vBMD was not different between sexes, but women had significantly more lumbar osteoporosis measured with AP DXA (P<0.001).
Men had significantly higher mSASSS (P<0.001).
Low BMD was associated with high age, disease duration, mSASSS, Bath Ankylosing Spondylitis Metrology Index (BASMI), inflammatory parameters and low body mass index (BMI).
Increasing mSASSS correlated significantly with decreasing lateral and volumetric lumbar BMD, while AP lumbar BMD showed tendency to increase.
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