A risk prediction tool unveiled in the 2013 American College of Cardiology and the American Heart Association cholesterol guidelines took another broadside hit with an analysis that tried to explain the difference in actual vs. calculated risks. The most recent salvo used data from the Women’s Health Study.

Authors Nancy R. Cook, ScD, and Paul M. Ridker, MD, of Brigham and Women’s Hospital in Boston, noted that the current calculator suggests nearly double the risk for patients over observed rates of atherosclerotic cardiovascular disease. Cook et al expressed concerns that this overestimation of risk may lead to more patients being prescribed statin regimens than would be considered wise.

Using data from the Women’s Health Study, Cook et al tried to understand why these calculated and observed rates were so far off. The Women’s Health Study enrolled 39,876 patients between Sept. 1992 and May 1995. Data used as part of this study were collected through March 2004 and represented a mean of approximately 10.2 years.

Even after adjustments, risks calculated through the guideline equations were 1.8 times or more higher in the lower risk cohorts and more than 1.3 times higher in the highest risk cohorts. These differences could not be reduced through under-ascertainment of events, statin use or revascularization procedures and were echoed in other studies using recent cohorts.

Cook et al suggested the possibility that some risks that could not be controlled for may have changed between the original development of the risk calculator, the data used to develop it and the present day. While Cook et al could not offer a means of mitigating the differences in risk, they recommended recalibration to capture a more true risk profile.

The findings were published online Oct. 6 in JAMA: Internal Medicine.

For more on the controversial guidelines, please read "Cholesterol Conundrum: Making Guidelines Work for You."