Background/Purpose : To compare clinical parameters in African American (AA) patients with ankylosing spondylitis (AS) to white patients.

Methods: 539 AS patients (47 B, 492 W), meeting the modified New York criteria f enrolled in a longitudinal outcome study were assessed cross-sectionally at the baseline visit.  Disease activity was defined by the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), functional outcomes by the Bath Ankylosing Spondylitis Functional Index (BASFI) and radiographic severity  by the Bath Ankylosing Spondylitis Radiographic Index (BASRI) and the modified Stokes Ankylosing Spondylitis Scoring System (mSASSS). Univariable comparisons of clinical characteristics for African-American and White patients were done using Chi-square test and Student t test and their non-parametric counterparts when necessary in both cohorts. We compared the baseline BASRI total score for African-American and White patients by constructing multivariable mixed effect models to account for intra-family correlation (539 patients from 449 families). Possible confounders were examined by identifying variables that were significantly associated with race and effect modifications were also tested while developing a final multivariable model. Analyses were performed using SAS 9.3 (SAS Institute Inc, Cary, NC) at a statistical significance level of 0.05.

Results: Blacks had greater radiographic severity as seen by higher BASRI scores (9.12 versus 6.41, p=0.0001), greater functional impairment as measured by the BASFI (53.65 versus 31.94, p=0.0001) and higher disease activity as determined by the BASDAI (5.52 versus 4.11, p=0.007) compared to whites. There was no difference between disease duration or age.  A significant interaction effect was found between race and disease duration. Table 1 shows the associations between baseline BASRI score and race at different levels of disease duration from the unadjusted and adjusted mixed effect model. Sex, B27+, study site and comorbidities (heart attack and diabetes) were adjusted in the final multivariable model. Subjective disease activity (BASDAI) and functional impairment (BASFI) were not included because data for African-American subjects were missing n some subjects. BASRI scores for African-American subjects were higher than those for Whites and this association got stronger as disease duration increased in both unadjusted and adjusted models.

Table 1. Associations between Baseline BASRI Score and Race at Different Levels of Disease Duration

Conclusion : Although we cannot rule out the possibility that the more severely affected AA with AS are properly diagnosed and/or volunteer for study, these data confirm and extend prior subjective assessments of greater disease severity in African Americans using objective clinical and radiographic measurements and validated outcome tools.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/blacks-with-as-have-greater-disease-severity-than-whites/