Radiographic joint damage in rheumatoid arthritis is associated with differences in cartilage turnover and can be predicted by serum biomarkers: an evaluation from 1 to 4 years after diagnosis

Table 2 Association between biomarker values measured at year 1 and subsequent radiographic progression rates

Biomarker	P value for interaction^a	Estimated annual progression rate
		Mean biomarker (%)^b	Mean + one standard deviation (%)^c
C2C
Damage	0.030*	29	35
Erosion	0.156	24	27
Narrowing	0.019*	31	40
C1,2C
Damage	0.033*	26	30
Erosion	0.195	25	29
Narrowing	0.271	32	36
CPII
Damage	0.777	28	28
Erosion	0.816	25	25
Narrowing	0.136	33	41
CS846-epitope
Damage	0.039*	28	34
Erosion	0.014*	27	36
Narrowing	0.476	32	35

For each biomarker, the results of the multivariable generalized estimated equation regression model for longitudinal analyses between biomarker value at year 1 after inclusion and subsequent (repeated over time) values of the log-transformed progression score are presented. C2C, marker for degradation of type II collagen in cartilage; C1,2C, marker for degradation of type I collagen and type II collagen in cartilage; CPII, marker for synthesis of the procollagen of type II collagen cartilage; CS846-epitope, marker for aggrecan turnover in cartilage. ^aP < 0.05 indicates that the change in the rate of progression depends significantly on the biomarker value at year 1; *interaction statistically significant (P < 0.05). ^bPercentage increase of radiographic damage score per year for patients with a mean value of biomarker 1 year after disease onset. ^cPercentage increase in radiographic damage scores per year for patients with a value one standard deviation above the mean biomarker value 1 year after disease onset.

ISSN: 1478-6362