Differences in multijoint radiographic osteoarthritis phenotypes among African Americans and Caucasians: the Johnston County Osteoarthritis project

Abstract

Objective: To define and contrast multiple joint radiographic osteoarthritis (OA) phenotypes describing hand and whole-body radiographic OA among African Americans and Caucasians.

Methods: We conducted a cross-sectional analysis in the Johnston County Osteoarthritis Project, using radiographic data for the hands, tibiofemoral (TF) joints, patellofemoral joints, hips, and lumbosacral (LS) spine. Radiographs were read for OA by a single radiologist using standard atlases. Fisher's exact test, with correction for multiple comparisons, was used to compare phenotype frequencies by race and sex. Logistic regression was used to provide odds ratios, which were adjusted for sex, age, and body mass index (BMI).

Results: Sixteen mutually exclusive hand (n = 2,083) and 32 whole-body (n = 1,419) radiographic OA phenotypes were identified. We found that in comparison to Caucasians, African Americans had significantly less frequent radiographic OA of the distal interphalangeal joints, both in isolation and in combination with other hand joint sites, but had comparable frequencies of radiographic OA for other hand joint sites. Moreover, African Americans had less frequent radiographic OA of the hand, both in isolation and in combination with other joint sites, as compared to Caucasians. In contrast, African Americans had more than twice the odds of isolated OA of the TF joint and 77% higher odds of radiographic OA of the TF joint and LS spine together as compared to Caucasians.

Conclusion: Even after adjustment for sex, age, and BMI, African Americans were less likely than Caucasians to have hand radiographic OA phenotypes, but more likely to have knee radiographic OA phenotypes involving the TF joint. African Americans may have a higher burden of multiple large-joint OA involvement not captured by most definitions of "generalized OA."

Figure 1. Flow chart of inclusion of individuals with radiographic data for hand and whole-body rOA phenotype assessments

Figure 2. Distribution of mutually exclusive hand rOA phenotypes by race

The frequency of each joint combination is shown, for African Americans (AAs) at the top and Caucasians at the bottome, sorted by frequency among Caucasians, to describe the overall shift in pattern for hand joint involvement among AAs.

Figure 3. Adjusted Odds Ratios and 95% CI for Whole-body rOA Phenotypes among African Americans compared to Caucasians

The adjusted odds ratios for African Americans (AAs) compared to Caucasians are shown, from those phenotypes least likely in AAs on the left to those most likely on the right. The point estimate of the aOR is shown with 95% CI indicated by the bars. The horizontal line is at an aOR=1 (no difference). A logarithmic scale is used due to the logarithmic nature of the ratio measures.