The BICOMBO study was a Spanish study that randomly assigned treatment-experienced participants to change the nuke portion of their regimen to one of the following:
The BICOMBO study team looked at a subgroup of participants from its study to assess the impact of nukes on the following:
The BICOMBO researchers noted that factors such as cardiovascular disease, diabetes, uncontrolled HIV infection or other health conditions might affect the risk of developing a heart attack. Not taking these factors into account could have inadvertently led to biases when interpreting the results of several studies in which abacavir was linked to an increased risk for heart attack. So the BICOMBO team proposed to do a sub-study in a smaller group of patients, examining factors that can increase CVD risk, and therefore heart attacks, before and after its study.
The BICOMBO sub-study focused on 46 participants who received abacavir + 3TC and 34 others who received tenofovir + FTC.
Some of the proteins they assessed in the blood included the following:
Levels of these and other proteins were similar between participants at the start of the study.
The average profile of people at the start of the BICOMBO study was as follows:
On the whole, people taking abacavir + 3TC did not have significant changes to levels of inflammatory proteins in their blood that were different from people taking tenofovir + FTC.
The researchers concluded that in otherwise-healthy participants the use of abacavir + 3TC compared to tenofovir + FTC did not result in significant differences in blood tests used to assess the following:
The BICOMBO team added that "these results argue against the involvement of abacavir in any of these mechanisms and therefore do not explain the higher risk of [heart attacks] associated with recent abacavir use in some cohort studies."
The strength of the BICOMBO study are as follows:
A weakness of BICOMBO is that it was a relatively small study. Another randomized study called STEAL, with a similar number of participants, found an unexpected increase in the risk of cardiovascular complications, including heart attacks, in treatment-experienced people who received abacavir + 3TC compared to others who received tenofovir + FTC. Some people in STEAL had pre-existing cardiovascular disease before taking that study's medication, particularly people who were assigned to receive abacavir.