Routine measurements of white blood cell counts that provide a ratio of neutrophils to lymphocytes may offer a simple and low-cost way to refine predictions of heart attack or death, according to a new study in the May 17, 2005, issue of the Journal of the American College of Cardiology.
“With additional validation and testing in other populations, I believe that this ratio could be added to the other risk factors we know of, in order to build an even stronger risk profile that would allow people to make decisions about lifestyle changes or maybe whether they need to have additional diagnostic tests. Perhaps in cases where patients’ blood pressures or cholesterol levels are borderline, this test could tip the balance between treating some patients and not treating others,” said Jeffrey L. Anderson, M.D., F.A.C.C., at the LDS Hospital and the University of Utah in Salt Lake City.
The researchers, including lead author Benjamin D. Horne, M.Stat., M.P.H., looked at blood test results from 3,227 patients who underwent coronary angiography at the LDS Hospital between 1994 and 2001. The subjects did not show signs of having suffered a heart attack immediately before the procedure. They all survived the hospitalization, and their records provided long-term follow-up averaging three-and-a-half years.
The risk of a subsequent heart attack or death was higher in those patients who had elevated total white blood cell counts. But looking beyond that total figure, to the subtypes of white blood cells, provided stronger predictions. In analyses that included multiple variables, patients with the highest levels of neutrophils had almost double the risk of those with the lowest levels. Conversely, those with the highest levels of lymphocytes had just half the risk of a heart attack or death compared to those with the lowest lymphocyte levels.
The strongest predictor came from combining those measurements into the ratio of neutrophils to lymphocytes. Patients with the highest ratios had more than double the risk of a heart attack or death of the patients with the lowest ratios.
“We are not sure exactly what role the white blood cells are playing, or whether it is good or bad; but the goal of this study was mainly just to show that they are predictive, and that this is a better predictive test, available at negligible extra cost, so why don’t we make use of it?” Dr. Anderson said.
These results appear to fit with the growing evidence that inflammation plays an important role in cardiovascular disease. However, Dr. Anderson pointed out that this study used the results of just a single blood test in each patient, and that there is no information yet about whether changes in white blood cell counts over time could be used as an indication of the progression of disease or the effectiveness of treatment.