Which measuring site in ankylosing spondylitis is best to detect bone loss and what predicts the decline: results from a 5-year prospective study

Table 6 Multiple linear regression analyses, ΔBMD (%) as adependent variable, with no exposure to TNFi or bisphosphonates.

Constant	Femoral neck		Total hip		Spine AP		Spine lateral		Spine vBMD		Total radius
	14.0		5.53		–16.4		–54.4		–47.6		3.58
	β	p	β	p	β	p	β	p	β	p	β	p
Baseline
BMD at same site, g/cm²	0.09	1.0	4.90	0.1	3.20	0.4	–6.94	0.3	–47.9	0.06	9.73	0.2
Age, years	–0.08	0.1	–0.02	0.6	0.03	0.6	0.03	0.7	–0.05	0.5	–0.11	0.005
Sex	–0.53	0.7	–0.75	0.4	–2.11	0.1	–1.42	0.5	–0.40	0.8	0.15	0.9
Pack years	0.17	0.01	0.07	0.08	0.12	0.07	0.20	0.04	0.16	0.07	–0.09	0.03
mSASSS, score	0.08	0.06	0.01	0.7	–0.07	0.1	–0.07	0.3	–0.03	0.6	0.02	0.5
During follow-up
Time between DXA, months	–0.27	0.4	–0.16	0.4	0.21	0.5	1.00	0.02	1.00	0.006	–0.09	0.6
Δweight, kg	0.05	0.7	0.25	0.001	0.38	0.001	0.60	0.001	0.61	0.001	0.04	0.5
NSAID-index, 0–100	0.01	0.3	0.01	0.4	0.03	0.08	0.03	0.2	0.021	0.3	0.01	0.2
Mean ESR last 5 years, mm/h	–0.19	0.01	–0.11	0.02	–0.09	0.3	–0.24	0.04	–0.21	0.04	NA
Mean CRP last 5 years, mg/L	NA		NA		NA		NA		NA		–0.14	0.06
R ²	0.21		0.32		0.27		0.28		0.34		0.29

Betas are unstandardized coefficients
Coding for sex: 0 = man, 1 = woman
Number of patients = 97
Significant p values are shown in bold typeface
AP anterior-posterior, BMD bone mineral density, CRP C-reactive protein, DXA dual-energy x-ray absorptiometry, ESR erythrocyte sedimentation rate, mSASSS modified Stoke Ankylosing Spondylitis Spine Score, NA not available, NSAID nonsteroidal anti-inflammatory drug, TNFi tumor necrosis factor inhibitor, vBMD volumetric BMD