Routine, inexpensive blood test sharpens heart disease risk predictions

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.

He said the results need to be confirmed and also studied in other types of patients. He pointed out that the study does not reveal why these white blood cell counts are associated with the risk of heart attack or death and that changes in white blood cell counts may be just a response to other facets of cardiovascular disease. He said the neutrophil/lymphocyte ratio should be seen as one more piece of information to be put into context with other heart disease risk factors.

“But it seems to be as predictive as the other things we look at, such as diabetes or high cholesterol or high blood pressure. It seems to be as predictive as age or severity of heart disease or family history and so forth. So it seems to be as good as those traditional risk factors, and probably as good as C-reactive protein, which has gotten a lot of publicity lately,” Dr. Anderson said.

William S. Weintraub, M.D., F.A.C.C., at the Emory University School of Medicine in Atlanta, who was not connected with this study, said that the key point is the ease and low cost of adding this test to routine clinical practice.

“The importance of this report is that this is a readily available, inexpensive test. It is important to develop less expensive means of predicting outcome. It is not clear that this will have therapeutic importance,” Dr. Weintraub said.

Matthew A. Allison, M.D., M.P.H., at the University of California in San Diego, who also was not associated with this study, noted the common use of white blood counts.

“These findings are clinically important since a routine, low cost test may be appropriate for stratifying future risk in those with symptoms of heart disease,” Dr. Allison said.

The American College of Cardiology, a 31,000-member nonprofit professional medical society and teaching institution, is dedicated to fostering optimal cardiovascular care and disease prevention through professional education, promotion of research, leadership in the development of standards and guidelines, and the formulation of health care policy.