Failure of serum transforming growth factor-beta (TGF-beta1) as a biomarker of radiographic osteoarthritis at the knee and hip: a cross-sectional analysis in the Johnston County Osteoarthritis Project.

PURPOSE: To assess associations between serum transforming growth factor-beta (TGF-beta1) and radiographic knee and hip osteoarthritis (rOA) in African American (AA) and White men and women.

METHODS

Baseline data from 330 participants in the Johnston County Osteoarthritis Project were used in the analysis. Radiographs were scored with the Kellgren-Lawrence scale and rOA defined as grade> or =2. Individual radiographic features (IRFs) were rated 0-3. TGF-beta1 was measured using a sandwich enzyme-linked immunosorbent assay (ELISA). General linear models were used to estimate associations between lnTGF-beta1 and rOA presence, laterality or severity, and IRF presence and severity, adjusting for age, gender, race and body mass index. Interactions by race and gender were considered significant at P<0.1.

RESULTS

Mean lnTGF-beta1 levels were higher among AAs compared to Whites, and among women compared to men (P<0.009). Mean lnTGF-beta1 levels were higher in those with knee osteophytes (OST), but this association was not significant after adjustment. There were no other significant differences in mean lnTGF-beta1 levels by presence, laterality, or severity of knee or hip rOA or IRFs. No race or gender interactions were identified, although a borderline significant association between lnTGF-beta1 and knee OST was seen among AAs (P<0.06).

CONCLUSIONS

Although serum TGF-beta1 varied by race and gender and several rOA variables, there were no independent significant associations with presence, laterality, or severity of knee or hip rOA by K-L grade or IRFs, suggesting that serum TGF-beta1 is unlikely to be useful as a stand-alone biomarker in OA studies. A possible association between TGF-beta1 and OST in AAs cannot be excluded.