A quarter of patients who are infected with human immunodeficiency virus (HIV) in the United States are also infected with Hepatitis C virus (HCV). When a person is infected with more than one virus, it is called a co-infection. Co-infected individuals have greater health problems than if they were just infected with just HIV or just HCV. Previous research has shown that people infected with both HIV and HCV have an increased risk of bone fractures and poorer bone health than people who are infected with just HIV. However, scientists do not yet know why. Low bone density is a common reason why people break bones, but people with HIV and HCV co-infections don’t necessarily have lower bone density than those infected with either virus alone. So, researchers at the VA North Texas Health Care System and the University of Texas Southwestern Medical Center at Dallas attempted to figure out why these differences exist.
The researchers used a new method of measuring bone health rather called a trabecular bone score that measures microscopic changes in the architecture and structure of bones. This new measurement can give doctors more information about bone health than the bone density measurements can.
To study these differences, the researchers enrolled 532 male patients in their study who were already receiving care at the VA North Texas Health Care System. These patients were placed into four different groups that included those infected with both HIV and HCV, those only infected with HIV, those only infected with HCV, and uninfected veterans (used as controls for the study). These patients all underwent both bone mineral density testing (the old method for testing bone health) as well as trabecular bone score testing (the new method of testing bone health) on the lumbar portion of their spine, the head of their femur, and their hips.
After taking into account each patient’s age, race, body mass index, and smoking status (traditional risk factors for poor bone health), the researchers confirmed previous studies that people infected with both viruses tend to have lower bone density than healthy people. However, the trabecular bone scores were able to show more detail. The researchers found that while there was no difference in trabecular bone scores between HIV positive patients and healthy patients, HCV-infected patients did show poorer scores. Furthermore, patients with both HIV and HCV infection had lower trabecular bone scores than all other patient groups.
It appears as though a simple bone density test is not enough to detect how these viruses affect the bones. Microscopic changes in bone architecture are only associated with HCV infection and not HIV infection. This could help explain why people with HCV infection and those with HIV/HCV co-infection have higher risk of bone fractures and poorer bone health than those infected with just HIV. This new method of assessing bone health could also be very helpful to doctors in the future to predict if someone infected with HCV will be at risk for bone fractures.