Sinus infections are one of the most common reasons patients walk out of the doctor's office with an antibiotic prescription in hand. The problem is that bacteria causes only about one–third of sinus infections, which means most patients are inappropriately receiving antibiotics.

To curb unnecessary antibiotic prescribing, physician and University of Georgia researcher Mark Ebell developed a clinical decision rule for diagnosing acute rhinosinusitis.

In a study appeared in the journal Annals of Family Medicine, Ebell, who is a professor of epidemiology at UGA's College of Public Health, presents a series of simple clinical rules that integrate patient symptoms and simple lab tests to accurately detect acute bacterial rhinosinusitis.

Though primary practice guidelines only recommend the use of antibiotics for patients who have experienced prolonged or severe symptoms, an estimated 72 percent of patients receive an antibiotic.

To develop a clinical decision rule for acute bacterial rhinosinusitis, Ebell needed to determine which combination of symptoms and tests best predicted the presence of bacteria and compare the statistical predictor to a reference standard, which is used to confirm its accuracy. A positive bacterial culture of sinus fluid was the preferred reference standard in this study.

He and his colleague, Dr. Jens Hansen of Aarhaus University Hospital in Denmark, recorded the symptoms and C–reactive protein levels for 175 patients suspected of having sinus infections. Based on these data, Ebell created a point score that can be used to determine the likelihood that a patient is at low, moderate or high risk for bacterial infection.

CRP tests detect inflammation in the body, which can indicate an infection. This is an important component of the point score, Ebell said, though CRP testing is currently unavailable in most primary care settings in the U.S.

Approximately half of patients in the study had a low score, meaning they were low–risk for bacterial infection. Withholding antibiotics from this group could cut the proportion of patients receiving antibiotics in half.

Ebell said that physicians can easily incorporate this point score into clinical practice. A nurse or medical assistant can identify whether patients are experiencing any of five symptoms – previous upper respiratory or sinus infections, discolored mucus, pain in the area under the eyes, or a toothache – during the initial interview. Then, the physician could decide whether to order a CRP test and determine a final score for sinus infection.

CRP tests have been shown to help better diagnose lower respiratory infections, pneumonia and, now, acute bacterial rhinosinusitis. Ebell hopes this study will encourage the Food and Drug Administration to loosen restrictions on its use in primary care clinics.

"If you can show a patient that his or her inflammation level is low, which makes bacteria an unlikely cause of infection, then I think patients might be more willing to accept not getting an antibiotic," he said.

Ebell's next plan is to perform a randomized clinical trial to test the effectiveness of the point score system, including the use of a CRP test, in clinical practice.

"We need to give physicians better tools to support their decision–making, and that can include clinical decision rules and point of care tests like CRP," Ebell said. "Using these kinds of tools, we can hopefully reduce unnecessary antibiotic use."

The study is titled, "Proposed Clinical Decision Rules to Diagnose Acute Rhinosinusitis Among Adults in Primary Care."