Measuring blood chemical may reduce antibiotic overuse for lower respiratory tract infections

The use of guidelines for treatment of lower respiratory tract infections such as bronchitis and pneumonia determined by measurements of a chemical in the blood known as procalcitonin resulted in lower rates of antibiotic use and associated adverse effects, and similar rates of adverse outcomes compared to standard guidelines, according to a study in the 9 September issue of JAMA.

"Unnecessary antibiotic use importantly contributes to increasing bacterial resistance and increases medical costs and the risks of drug-related adverse events. The most frequent indication for antibiotic prescriptions in the northwestern hemisphere is lower respiratory tract infections (LRTIs),which range in severity from self-limited acute bronchitis to severe acute exacerbation of chronic obstructive pulmonary disease (COPD), and to life-threatening bacterial community-acquired pneumonia (CAP)," the authors write. The researchers add that clinical signs and symptoms are unreliable in distinguishing viral from bacterial LRTI, and that as many as 75 percent of patients with LRTI are treated with antibiotics despite the predominantly viral origin of their infection.

An approach that has been suggested to estimate the probability of bacterial origin in LRTI is the measurement of serum procalcitonin (PCT), with evidence from smaller trials suggesting that use of clinical algorithms (a procedure consisting of a sequence of steps to calculate or determine a specific output) based on certain PCT measurements could lead to needed reductions in antibiotic use, according to background information in the article. Levels of this chemical are high in patients with a bacterial infection but low in those with a viral infection.

Philipp Schuetz, MD, of University Hospital Basel, Switzerland, and colleagues conducted a large, multicentre trial to compare use of PCT guidelines with standard guidelines and subsequent antibiotic use. The study, conducted at 6 tertiary care hospitals in Switzerland, included 1,359 patients with mostly severe LRTIs. Patients were randomised to administration of antibiotics based on a PCT algorithm with predefined cutoff ranges for initiating or stopping antibiotics (PCT group) or according to standard guidelines (control group). Serum PCT was measured locally in each hospital.

The researchers found that "the rate of overall adverse outcomes was similar in the PCT and control groups [15.4 percent vs. 18.9 percent]. The mean [average] duration of antibiotics exposure in the PCT vs. control groups was lower in all patients [5.7 vs. 8.7 days; relative change, -34.8 percent] and in the subgroups of patients with community-acquired pneumonia [n = 925, 7.2 vs. 10.7 days; -32.4 percent], exacerbation of chronic obstructive pulmonary disease [n = 228, 2.5 vs. 5.1 days; -50.4 percent], and acute bronchitis [n = 151, 1.0 vs. 2.8 days; -65.0 percent]. Antibiotic-associated adverse effects were less frequent in the PCT group [19.8 percent vs. 28.1 percent]."

"In conclusion, particularly in countries with higher antibiotic prescription rates than Switzerland, PCT guidance will have substantial clinical and public health implications to reduce antibiotic exposure and associated risks of adverse effects and antibiotic resistance," the authors write.

(Source; JAMA/Archives: JAMA: September 2009)