Test Predicts Death From Sickle Cell
High Levels of BNP Protein in Blood Marks Greater Odds of Dying in Sickle Cell Patients
Dec. 14, 2005 (Atlanta) -- A blood test used to detect heart disease may predict death in people with sickle cell anemia.
National Heart, Lung, and Blood Institute( NHLBI) researchers have found that BNP (brain natriuretic peptide) testing, which helps predict death in patients with heart failure, effectively detects pulmonary hypertension and death in sickle cell anemia.
The management of patients with sickle cell disease has improved dramatically, although many patients still have life-threatening but potentially treatable problems, says James N. George, MD. George is president of the American Society of Hematology and professor of medicine at the University of Oklahoma Health Sciences Center.
"This important study provides new insight for identifying patients at risk for critical complications." he adds. Researchers reported the findings at the 47th Annual Meeting of the American Society of Hematology.
Silver Lining for Sickle Cell
Sickle cell disease is a blood disorder affecting the oxygen carrying capacity of blood cells. Distorted, fragile, and sickled blood cells block blood vessels, causing tissue death. The disease results in lung damage, painful episodes, stroke, and damage to the spleen, kidneys, and liver.
"Pulmonary hypertension is one of the major complications of sickle cell and is the most important cause of death," notes Robert F. P. Machado, MD, a staff physician and researcher at the vascular medicine branch, NHLBI and critical care medicine department, National Institutes of Health in Bethesda, MD.
Pulmonary hypertension causes high blood pressure within the vessels of the lungs; the increases in pressure above normal can be life threatening. These elevations cause strain on the heart, which must then work harder to pump blood to the lungs for oxygenation.
Symptoms include shortness of breath with minimal exertion, fatigue, chest pain, dizzy spells, and fainting.
When under severe strain, the heart releases a protein called brain natriuretic peptide, or BNP; the protein is elevated when the heart is damaged.
"We borrowed this test from cardiology," Machado said, during a news conference. "It's a hormone that is secreted by the heart ventricles in response to heart muscle cells being stretched by overload. Now we have taken the marker to the world of sickle cell disease."
Blood Test Breakthrough
Researchers measured BNP levels in 230 sickle cell disease patients with moderately severe disease and 45 healthy controls. They show that BNP levels were higher in sickle cell patients with pulmonary hypertension than in those patients without the condition and in healthy controls.
Additionally, abnormally high levels of the protein (greater than 160) predicted death, increasing the risk of death by twofold in sickle cell patients with pulmonary hypertension.
The researchers then looked at levels of the protein in banked blood samples of 121 patients with sickle cell anemia who had been enrolled in another study back in 1996.
"The higher the severity of pulmonary hypertension, the higher the BNP levels," says Machado.
For years, pulmonary hypertension "was flying under the radar screen" in treatment of patients with sickle cell anemia, he tells WebMD. "Now we have discovered a biomarker that can be applied to a large cohort of patients and provide important diagnostic information."
"This is an exciting new observation for patients with sickle cell anemia," says George. "The major cause of mortality is the buildup of pressure in the vessels of the lungs, pulmonary hypertension. Now there is a blood test that can predict the abnormality and lead to better management of these patients."