Bone phenotypes in rheumatology – there is more to bone than just bone

Table 5 Biomarkers at the bone cartilage interface in AS

Biomarker	Disease Levels compared to healthy	Findings	References
Bone turnover
CTX-I	Increased	Associated with radiographic progression No effect of anti-TNFα therapy	[229, 230, 233, 234]
ICTP	Increased	–	[235]
PINP	No difference	Correlated with radiographic progression of syndesmophytes and ankylosis	[226, 229,230,231,232,233]
Osteocalcin	No or limited difference	Associated with syndesmophytes and ankylosis	[226, 229,230,231,232]
BALP	No or limited difference	–	[226, 229,230,231,232,233]
Cartilage Turnover
CTX-II	Increased	Correlated with change in clinical disease severity in response to anti-TNFα therapy	[229, 236]
C2M	Increased	–	[237]
C2C	No difference	–	[238]
PIIANP	Increased	–	[192]
PIIBNP	Increased	–	[193]

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