For hospitalized patients with community-acquired pneumonia (CAP), lower measurements of procalcitonin, a biomarker of infection, can reduce the length of antibiotic treatment by an average of seven days.

The study, which is the first research trial of its kind, appears in the first issue for July 2006 of the American Journal of Respiratory and Critical Care Medicine, published by the American Thoracic Society.

Beat Mller, M.D., of University Hospital in Basel, Switzerland, and nine associates examined 302 consecutive patients with suspected CAP. They divided the study cohort into 151 control subjects who received antibiotics according to usual practice, and 151 patients who were given antibiotics based on higher or lower levels of procalcitonin in their blood. (Procalcitonin is elevated in bacterial infections.)

Pneumonia, which involves inflammation of the lung caused by bacterial infection, viruses or other organisms, can be fatal, especially in the elderly. In 2003 alone, 63,241 people died from pneumonia in the U.S.

"CAP is also the major infection-related cause of death in developed countries," said Dr. Mller. "Approximately 10 to 20 percent of hospitalized patients with CAP must be admitted to the intensive care unit, where 20 to 50 percent will ultimately die."

For bacterial CAP, promptly initiating antibiotic therapy is commonly considered the key to survival, he added, "as a delay of more than 4 hours can be associated with increased mortality."

Yet, within the two study groups, doctors withheld antibiotics upon admission to the hospital in 15 percent of the procalcitonin group and in 1 percent of the control group.

In more than 70 percent of CAP presumed to be of bacterial origin, the causative microbe could not be identified in the lab. Therefore, the results from bacterial cultures are not considered central to the clinical care of the patient.