[Contemporary clinical diagnostics of respiratory tract infections].

The patient population at risk pulmonary infections has increased during the last decade. The spectrum of organisms causing infections has also grown, most of them are viruses Baseline diagnostic assessment include history, clinical examination, radiography and measurements of procalcitonin (PCT), highly sensitive C-reactive protein (hsCRP) and leukocyte count. PCT represents a good biological marker for difficult diagnoses in critically ill patients and is superior to CRP. Chest x-rays seldom give enough information to determine the exact cause of the abnormality, but they can help a doctor to determine whether and which other tests are needed to make a diagnosis. Microbiologic advances have helped to facilitate the laboratory diagnosis of some pathogens. Cultures of respiratory specimens are some times useful but the gold standard for diagnosis of pulmonary infection is blood culture. Immunoassays are available for the detection of antigen in nasopharyngeal secretions (respiratory syncytial virus, influenza), and in urine (Legionella spp.). Rapid-culture techniques are available for the culture and detection of various viruses. Recently PCR-based techniques and RT-PCR assist in the detection of Legionella, Chlamydia, Mycoplasma, Pneumocystis carinii and mycobacteria species. This article presents a practical approach to the differential diagnosis of pulmonary infections.