• Daiana Stolz, Mirjam Christ-Crain, Mikael M Gencay, Roland Bingisser, Peter R Huber, Beat Müller, and Michael Tamm.
• Division of Pulmonary Medicine and Cell Research, University of Basel, Basel, Switzerland. DStolz@uhbs.ch
• Swiss Med Wkly. 2006 Jul 8; 136 (27-28): 434-40.

BackgroundLower respiratory tract infections (LRTI) account for the majority of all antibiotics prescribed in the clinical practice, irrespective of the fact that most cases are self-limiting. Using the outcome and microbiology findings as gold standard, we determined sensitivity, specificity, positive and negative predictive values of common used signs and symptoms of bacterial LRTI requiring antibiotic therapy.Patients243 consecutive patients with suspected LRTI admitted to a tertiary care hospital.ResultsBacterial LRTI requiring antibiotic therapy and self-limiting LRTI were diagnosed in 32 and 86 patients, respectively. Assessing these two groups, sputum, dyspnea, crackles, fever and leukocytes (WBC) were insensitive and unspecific parameters for the diagnosis of bacterial LRTI requiring antibiotic therapy. Cough was sensitive (93.8%) but unspecific (5.8%). The sensitivity of infiltrates, C-reactive protein (CRP) >50 mg/L and procalcitonin (PCT) >0.1 ng/mL was 96.9%, 93.8% and 93.8%, respectively. PCT >0.25 ng/mL showed the highest specificity (97.7%), followed by WBC >16 x 109/L (94.2%) and CRP >100 mg/L (91.9%). The sensitivity of WBC >16 x 109/L was low (37.5%).ConclusionThe overall sensitivity and specificity of signs and symptoms for bacterial LRTI requiring antibiotic therapy was poor. Obtaining a chest-X-ray with infiltrates and determining CRP at a cut-off value of 50 mg/L or PCT at a cutoff value of 0.1 ng/mL was required to ascertain the need for antibiotics in LRTI.

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