medwireNews: The incidence of giant cell arteritis (GCA) is similar among Black and White people, suggests an analysis of a cohort from a US tertiary care center.
“Our findings are notable in that they appear to contradict the commonly held belief that GCA is rare in black compared with white patients,” write Anna Gruener (Nottingham University Hospitals NHS Trust, UK) and team in JAMA Ophthalmology.
“Based on previous epidemiological data, many physicians may have a higher threshold for TAB [temporal artery biopsy] in black patients, but our findings suggest this should not be the case,” they add.
The authors of a related commentary, however, highlight certain methodologic issues, such as the use of US census data for standardizing the incidence rates instead of the local racial distribution and the inclusion of healed cases, which they believe “will increase the rate of false-positive results, which could lead to a spurious conclusion about the risk of arteritis among races.”
Therefore, Michael Yoon and Joseph Rizzo III, both from Harvard Medical School in Boston, Massachusetts, USA, caution physicians “not to use race as a significant factor in determining suspicion of GCA” until these results are reproduced in future confirmatory studies.
Of 586 individuals who underwent TAB between 2007 and 2017 at the Johns Hopkins Wilmer Eye Institute in Baltimore, Maryland, 28.5% were Black, 65.2% were White, and the remaining 6.3% were of another or unknown ethnicity. Only the 573 people who were at least 50 years of age were included in further analyses, “because the concept of GCA in patients younger than 50 years is controversial,” explain the study authors.
GCA was confirmed on TAB for 92 individuals, of whom 14 were Black and 75 were White, equating to 8.4% and 19.6% of all Black and White patients, respectively. The corresponding crude annual incidence rates were 2.9 and 4.2 per 100,000 individuals, and Black individuals were significantly less likely to have a positive TAB result than White people, a finding that was confirmed on multivariable analysis.
But when the findings were standardized using the 2010 US census data, the age- and sex-standardized rates per 100,000 individuals were 3.1 and 3.6 for Black and White patients, respectively, with no significant difference between the groups.
Similarly, the incidence rate ratio was 1.2 for White versus Black individuals, but again this was not statistically significant.
“These findings do not appear to support the conclusion that GCA occurs more frequently in white compared with black patients,” summarize Gruener and colleagues.
Despite their methodologic concerns, the commentators commend the researchers “for questioning commonly held views,” and add: “Although the authors’ methods are imperfect, the studies that had previously established a low incidence of GCA in black patients were also flawed in design.”
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JAMA Ophthalmol 2019; doi:10.1001/jamaophthalmol.2019.2919
JAMA Ophthalmol 2019; doi:10.1001/jamaophthalmol.2019.2933