Association of markers of bone- and cartilage-degradation with radiological changes at baseline and after 2 years follow-up in patients with ankylosing spondylitis.
OBJECTIVE
There is a lack of knowledge on factors that reliably can predict radiological changes in patients with AS. We have investigated whether urinary C-terminal cross-linking telopeptide of type I (CTX-I) and type II (CTX-II) collagen, as specific biochemical markers of bone and cartilage degradation, respectively, are associated with radiological damage and progression, and with BMD in patients with AS.


METHODS
Eighty-three patients with AS [mean (s.d.) age: 50.4 (12) yrs, 65% male, mean (s.d.) disease duration after diagnosis: 16.7 (10) yrs] who participate in an ongoing cohort study of patients with AS [Outcome in AS International Study (OASIS) cohort] were assessed for urinary CTX-I and -II. Results of both biochemical markers were compared with baseline scores for radiological damage (modified modified Stoke Ankylosing Spondylitis Spine Score, primarily reflecting syndesmophyte-formation and -growth), and with scores for radiological progression after 2 yrs follow-up. Markers were also associated with disease activity parameters and BMD.


RESULTS
Mean duration of complaints was 28.6 yrs. At that time, 54% of patients had signs of radiological damage, and 35% of them showed radiological progression after 2 yrs. Baseline radiological damage (rho = 0.24; P <or= 0.05) correlated with CTX-II, but not with CTX-I. CTX-II correlated with serological markers of inflammation (ESR rho = 0.29 and CRP rho = 0.30; P <or= 0.01), but not with baseline BASDAI or BMD. There was a negative correlation between CTX-I and BMD of the trochanter (rho = -0.31; P <or= 0.01) In multivariate analyses, CTX-II significantly and independently contributed to explaining variation in radiological damage (standardized beta = 0.27; P = 0.03) and progression (standardized beta = 0.27; P = 0.05).


CONCLUSIONS
In AS, cartilage degradation plays a role in explaining radiological-damage and -progression in the spine.
Department of Internal Medicine, Division of Rheumatology, University Hospital Maastricht, PO Box 5800, 6202 AZ Maastricht, The Netherlands. dvo@sint.azm.nl
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Vosse
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Landewé
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Garnero
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van der Heijde
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van der Linden
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Geusens
D000328:Adult; D015415:Biomarkers / Q000652:urine; D015519:Bone Density; D001862:Bone Resorption / Q000209:etiology* / Q000652:urine; D002097:C-Reactive Protein / Q000378:metabolism; D002358:Cartilage, Articular / Q000378:metabolism*; D024042:Collagen Type I / Q000652:urine; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D010455:Peptides / Q000652:urine; D011859:Radiography; D012720:Severity of Illness Index; D013167:Spondylitis, Ankylosing / Q000150:complications* / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000652:urine
D015415:Biomarkers; D024042:Collagen Type I; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide; D002097:C-Reactive Protein