White and black patients have similar rates of giant cell arteritis

Although giant cell arteritis (GCA) had been established in previous studies as more common in white populations, a new study in JAMA Ophthalmology with a larger sample of black patients found similar incidence rates between black and white individuals.

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To determine the incidence of biopsy-proven GCA (BP-GCA) in a racially diverse cohort, Anna M. Gruener of Nottingham (England) University Hospitals NHS Trust and coauthors analyzed the medical records of more than 10 years of patients who underwent temporal artery biopsy at Johns Hopkins Wilmer Eye Institute in Baltimore. Of the 586 patients in the study, 167 (28.5%) were black, 382 (65.2%) were white, and 37 (6.3%) were other or unknown. The mean age was 70.5 years.

Of the 573 patients who were aged 50 years and older, 92 (16.1%) had a positive biopsy for BP-GCA; 14 were black (8.4% of all black patients), 75 were white (19.6% of all white patients), and 3 were other or unknown. The population-adjusted, age- and sex-standardized incidence rates per 100,000 were 3.1 (95% confidence interval, 1.0-5.2) for black patients and 3.6 (95% CI, 2.5-4.7) for white patients.

Overall, BP-GCA occurred more frequently in women than in men (incidence rate ratio, 1.9; 95% CI, 1.1-3.4; P = .03) but at similar levels in white and black patients (IRR, 1.2; 95% CI, 0.6-2.4; P = .66).

In an accompanying editorial, Michael K. Yoon, MD, and Joseph F. Rizzo III, MD, of Harvard Medical School, Boston, praised the researchers for conducting their study in a population with a large percentage of black patients, a noted weakness of earlier studies in this area (JAMA Ophthalmol. 2019 Aug 8. doi: 10.1001/jamaophthalmol.2019.2933). That said, the two doctors also recognized the limitations of the work done by Gruener et al., including relying on U.S. Census data to calculate adjusted incidence rates instead of local racial distribution and also the potentially problematic choice to count patients with healed arteritis as having BP-GCA.

Still, Dr. Yoon and Dr. Rizzo commended Gruener et al. for questioning previous findings on GCA rates. “Although the authors’ methods are imperfect,” they wrote, “the studies that had previously established a low incidence of GCA in black patients were also flawed in design.”

The study had no outside funding source, and no conflicts of interest were reported.

SOURCE: Gruener AM et al. JAMA Ophthalmol. 2019 Aug 8. doi: 10.1001/jamaophthalmol.2019.2919.