(Reuters Health) - People who don’t understand how their health insurance works or how to estimate out-of-pocket costs are more likely to avoid needed care than those with a firm grasp of what services should cost, a U.S. study suggests.

Researchers surveyed 506 insured adults to determine their “health insurance literacy,” or how much they know about which preventive services – such as vaccinations and cancer screenings - should be provided at no cost and which come with out-of-pocket fees like co-payments and deductibles.

Researchers gave participants health insurance literacy scores ranging from 0 to 84, with lower scores indicating less familiarity with covered benefits and how much services cost. The average score was about 64.

Each 12-point increase in scores was associated with a 39 percent lower likelihood that people would delay or skip preventive health services and a 29 percent lower chance that people would do this for other types of care, the study found.

Overall, however, 30 percent of participants said they had postponed or avoided care altogether because of costs.

“It was surprising that low health insurance literacy was associated with avoidance of so many different kinds of healthcare services - from getting a cholesterol check or flu shot, to an urgent visit with a doctor,” said lead study author Dr. Renuka Tipirneni of the University of Michigan in Ann Arbor.

Under the Affordable Care Act (ACA), also known as Obamacare, health plans must cover 21 preventive health services for adults at no cost to consumers (bit.ly/1OxO6qw). These include recommended vaccinations as well as screenings for HIV, certain cancers and chronic health problems like diabetes and high blood pressure.

Many people remain unaware that these preventive health services are available to them at no charge, the study team notes in JAMA Network Open.

As a result, it appears that some people may be missing out on care out of a mistaken belief that they can’t afford it, even when it may be free, Tipirneni said by email.

“That’s important, because it can lead to people skipping basic care that can prevent infections, screen for cancer or diagnose health conditions,” Tipirneni added.

Low health literacy appeared to contribute to delayed and missed care even after researchers accounted for other factors like education and income levels that can independently influence these choices.

All but one of the survey participants had a high school diploma, and three in four of them had a two-year or four-year college degree.

The study can’t prove whether or how health insurance literacy might directly impact care decisions or if it influences health outcomes. And because the survey was from 2016, the results may not reflect Americans’ familiarity with the health plans they have today.

Still, the findings suggest that people might get better care if they better understood how health insurance works, said Dr. Jennifer Goldstein of the Christiana Care Health System based in Wilmington, Delaware.

“It’s important to seek out information in plain language from trusted sources about health insurance benefits,” Goldstein, who wasn’t involved in the study, said by email. “A better understanding of how coverage works can help individuals access the care they need to stay healthy.”

SOURCE: bit.ly/2OXa4qT JAMA Network Open, online November 16, 2018.