A likely 50,000 veterans have hepatitis C virus (HCV) but don’t know it, and four in five baby boomers (those born between 1945 and 1965) living with the virus who receive care in four health care systems may also be undiagnosed, aidsmap reports. Further research suggests that self-disclosed risk factors may not serve as effective means to screen for hep C among pregnant women, missing close to three-quarters of infections in this population. The various studies were presented at the 64th Annual Meeting of the American Association for the Study of Liver Diseases (AASLD) in Washington, DC.

An analysis of the Veterans Health Administration database of 5.5 million veterans in care looked for the proportion of those who had a medical appointment in 2012 and who received a hep C test between 1999 and 2012. Fifty-four percent of all vets had received at least one test, including 41.5 percent of those born before 1945, 64.2 percent of baby boomers and 58 percent of those born after 1965. A total of 1.7 percent of the oldest group had hep C, compared with 9.9 percent of the boomers and 1.1 percent of the youngest group.

Considering this data, the researchers projected that if all of the 905,000 boomers who had never received a hep C test did so, it would turn up an additional 51,000 cases of the virus.

The American College of Obstetricians and Gynecologists advises hep C tests for pregnant women only when there are “significant risk factors.” However analyzing over 32 million deliveries or miscarriages, researchers looked at the 28,663 mothers with hep C and found that nearly three-quarters of the women had no such risk factors listed in their files.

Finally, investigators conducted an analysis of 209,076 people in four medical sites who had at least one appointment between 2005 and 2010. A total of 17,464 (8.4 percent) had received a hep C test; out of that group, 6.4 percent tested positive. Three out of four of the positive tests were among baby boomers. The researchers projected that if all 209,076 people in the group received hep C tests, it would uncover an additional 6,005 cases of the virus. An estimated 81 percent of hep C infections in the overall group have not been diagnosed, the investigators estimated.

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