ASSOCIATION BETWEEN URINARY CTX-II, SERUM HYALURONIC ACID AND RADIOLOGICAL SEVERITY IN SYMPTOMATIC KNEE OSTEOARTHRITIS

Background: Urinary type II collagen C-telopeptide degradation products (U-CTX-II) is a marker of degradation of collagen, the most abundant protein of cartilage, and serum hyaluronic acid (S-HA) is a marker of synovial inflammation. Recent studies suggest that these markers could reflect structural damage in arthritis.Objectives: The objective of this study was to analyze the associations between the levels of U-CTX-II and S-HA and the clinical and radiological severity of knee osteoarthritis (KOA).Methods: From the baseline data of an on-going randomized clinical trial on the effect of chondroitin sulphate in KOA according to ACR criteria, all patients having an X-ray of both knees and CTX-II and HA measurements were included in the current analysis. Inclusion criteria were: Lequesne Algo-Functional Index (AFI) ≥ 6 and a pain score ≥ 40 mm on a 100-mm visual analogue scale (VAS). The AP tibio-femoral radiographs of both knees were read centrally and scored for Kellgren-Lawrence (KL), the number of osteophytes (from 0: none to 3: voluminous) and the degree of joint space narrowing (JSN: absent, 25%, 25 to 50%, >50%, and 100%). Urinary CTX-II (ng/mmol of creatinine) and S-HA (mg/mL) were measured in a specialized laboratory by ELISAs. A global radiological score per patient was obtained by adding the scores for both knees. Associations between U-CTX-II, S-HA and the radiological parameters were also analyzed by the GEE method (Generalized Estimating Equation: statistical method taking into account the fact that both knees belong to the same patient). All results were adjusted for age, sex and BMI.Results: In the 225 patients included (72% women; mean age: 66 years; mean BMI: 29 kg/m) the following results were obtained:- Adding radiological scores of both knees gave similar results than the GEE method, thus validating the summing method.- U-CTX-II correlated positively and significantly with all radiological parameters (KL: r=0.24; p<0.001; osteophyte: r=0.30; p<0.001 and JSN: r=0.23; p<0.001)- The correlation between S-HA and radiological severity was significant for the osteophyte score [r=0.21; p=0.002] and borderline significant for KL [r=0.13; p=0.051] and JSN [r=0.12; p=0.064]- There was no association between the clinical indices (AFI, pain on VAS) and the radiological or biological parameters (CTX-II or S-HA).Conclusion: U-CTX-II and, to a lesser extend, S-HA are associated with the structural severity in symptomatic KOA and may be used as biological markers for the severity of the disease. This correlation appears to be strongly linked to osteophytes.Citation: Ann Rheum Dis, volume 64, supplement III, year 2005, page 484Session: Osteoarthritis – Clinical aspects and treatment