A common blood test may miss ovarian cancer in some Black and Native American patients, delaying their treatment, a new study finds. It’s the latest example of medical tests that contribute to health care disparities.

Researchers have been working to uncover these kinds of biases in medicine. Recently, the Trump administration’s crackdown on diversity, equity and inclusion has jeopardized such research as universities react to political pressure and federal agencies comb through grants looking for projects that violate the president’s orders.

Native American women have the highest rate of ovarian cancer. Black women with ovarian cancer have lower rates of survival compared to white women. Finding ovarian cancer early can lead to better chances of survival.

The new study, supported by grants from the National Cancer Institute and published Thursday in JAMA Network Open, looked at a test called CA-125. The test measures a tumor marker in the blood, and doctors use it to determine if a woman with a suspicious lump should be referred to a cancer specialist.

Doctors depend on the test during early evaluations, so understanding what the results mean for people of different races and ethnicities is critical, said Dr. Shannon Westin of MD Anderson Cancer Center in Houston, who was not involved in the research.

“This is a perfect example of work that absolutely needed to be stratified based on race and ethnicity,” Westin said. The findings alert doctors that they shouldn’t be totally reassured by a normal test result, she said.

So far, it’s unknown why the test doesn’t perform uniformly across groups. The researchers suspect it has something to do with a harmless genetic variation that is more common in people of African, Caribbean, Middle Eastern and West Indian descent.

Initial studies of the test, published in the 1980s, didn’t record people’s races but were in mostly white populations.

The test isn’t perfect for white women either, said lead author Dr. Anna Jo Smith of the University of Pennsylvania’s medical school.

“But if we have worse performance in certain groups, then we may be further contributing to disparities in referral, disparities in treatment, and ultimately we may be contributing to the lower survival in Black women with ovarian cancer,” Smith said.

The researchers analyzed data from more than 200,000 women with ovarian cancer from 2004 through 2020 who’d had a CA-125 blood test.

Black and Native American patients were 23% less likely to have an elevated CA-125 level at ovarian cancer diagnosis compared with white patients, suggesting the current thresholds are set too high.

The researchers also found that patients with false negative results started chemotherapy on average nine days later than patients with elevated levels. That could make a difference for some patients, Smith said.

Last week, Smith and her colleagues presented work at a Society of Gynecologic Oncology meeting proposing a new lower threshold for the blood test that would work better across all populations. The work could lead to changes in guidelines.

“New thresholds for referral will ensure that all patients get in for rapid care when ovarian cancer is suspected,” Smith said.

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