Higher levels of CRP found in women and blacks

The study raises questions about whether risk thresholds should be adjusted for these groups.

Women tend to have higher levels of C-reactive protein than men, and blacks tend to have higher levels than whites, suggesting a need to reevaluate risk thresholds.

The current threshold for defining high relative risk with CRP is a measurement >3 mg/L.

“We found that a greater percentage of women had CRP levels above 3 mg/L, yet women have a lower risk of cardiovascular events. This implies that perhaps the cut-offs that we use in CRP to indicate different risk levels may have to be adjusted for different race and gender groups,” said Amit Khera, MD, director of preventive cardiology at UT Southwestern Medical Center.

His research was published in the Journal of the American College of Cardiology, with data from the Dallas Heart Study.

“This is a cross-sectional study so we really don’t know if the racial differences in CRP reflect differences in cardiovascular outcomes down the road,” Khera told Cardiology Today. “We don’t know because no one has really studied C-reactive protein levels very thoroughly in minority populations.”

The Dallas Heart Study, a multi-ethnic, population-based, probability sample, enrolled 2,749 patients: 475 white men, 516 white women, 740 black men, and 1,018 black women. The mean age of the patients was about 44 years.

Compared with white patients, black men and women had a significantly higher prevalence of diabetes and hypertension. Black women had a higher BMI and used estrogen supplements less often than white women. Black men had the highest prevalence of tobacco use.

Blood samples were obtained after an overnight fast in ethylenediamine tetra-acetic tubes. High sensitivity CRP measurements were performed on thawed samples using the Roche/Hitachi 912 System, Tina-quant assay (Roche Diagnostics), a latex-enhanced immunoturbidimetric method.

Black patients had higher levels of CRP than white patients with a median of 3 mg/L vs. 2.3 mg/L, respectively (P<.001). Women also had higher levels than men at a median of 3.3 mg/L vs. 1.8 mg/L, respectively (P<.001).

Researchers adjusted for the sample weights and found that CRP levels ≥3 mg/L were present in 31% of white men, 40% of black men, 51% of white women and 58% of black women in Dallas County.

Using white men as the comparator, researchers calculated odds ratios for increased CRP after adjustment for traditional cardiovascular risk factors, estrogen and statin use, and body mass index. A CRP level ≥3 mg/L remained more common in white women (OR=1.6; 95% CI, 1.1 to 2.5) and black women (OR=1.7; 95% CI, 1.2 to 2.6), but not in black men (OR=1.3; 95% CI, 0.8 to 1.9).

“C-reactive protein has taught us a lot about inflammation and heart disease. This study confirms that we need to take a closer look at racial and gender differences with this measurement to determine its appropriate use in multiethnic populations with high levels of obesity,” Khera said. – by Jeremy Moore

For more information:

• Khera A, McGuire DK, Murphy SA, et al. Race and gender differences in C-reactive protein levels. J Am Coll Cardiol. 2005;46:464-9.