Baby boomers have higher rates of hepatitis C infections than other age groups, and treatment is critical to reducing rising rates of liver cancer. (Getty Images)

Testing for hepatitis C, a major cause of liver cancer, is lagging behind among the group of Americans with the highest rate of infection: baby boomers.

A study published Tuesday showed that only about 13 percent of baby boomers were tested in 2015, up just slightly from 12 percent in 2013. U.S. public health authorities recommend all people in that demographic — those born between 1945 and 1965 — be screened for hepatitis C.

“If we want to make a dent in the rising rate of liver cancer, we need to get the population with a high rate of infection screened and treated,” said Susan Vadaparampil, the study's senior author and a researcher at Moffitt Cancer Center in Tampa.

While mortality rates for many cancers are decreasing, deaths from liver cancer rose 56 percent from 2003 to 2012. The strongest single predictor of the disease is chronic hepatitis C infection. Almost 80 percent of the people in the United States who have hepatitis C infections are baby boomers.

Most contracted the virus long before it was discovered in 1989. Many do not have any symptoms and do not realize they are infected. Vadaparampil said researchers are not sure why the infection rate in this group is so high but suspect it may be linked to past use of illicit injected drugs or other risky behaviors.

Screening for hepatitis C traditionally was based on whether a person was considered at risk because of drug use or specific medical conditions. In 2012, after research showed the prevalence of infections among baby boomers, the Centers for Disease Control and Prevention recommended that all get a one-time blood test to screen for the virus. The U.S. Preventive Services Task Force issued a similar recommendation in 2013. Screening for other age groups is still based on an assessment of risk factors.

In 2014, the Food and Drug Administration approved the first complete treatment — one that did not require the simultaneous use of other medicines — for hepatitis C. That drug, marketed as Harvoni and initially costing $94,500 for a 12-week regimen, cures the overwhelming majority of people with the disease.

To see whether the changes in treatment options and national screening guidelines affected screening rates among baby boomers,  researchers analyzed data from 2013 to 2015 in the National Health Interview Survey, a government survey based on household interviews.

The scientists found hepatitis C screening among baby boomers increased less than 1 percentage point during that period. The study was published in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.

The screening rate “isn't increasing in a meaningful way,” said Anna Giuliano, founding director of the Center for Infection Research in Cancer at Moffitt.

The researchers said a major limitation of the study was its reliance on self-reported data, because people sometimes do not remember accurately whether they have gotten a specific test.

Read more:

The cancer death rate has dropped again. Here's why.

CDC warns about salmonella infections traced to kratom

5 questions about the brain cancer diagnosed in Sen. John McCain