Efficient diagnosis of Pneumocystis carinii pneumonia

In patients with HIV infection the diagnosis of PCP is relatively simple when patients present late, with advanced pneumonia. The diagnosis becomes more difficult when patients present with minimal symptoms, are receiving specific prophylactic therapy or have had previous AIDS-related pulmonary diseases. A number of non-invasive tests, such as Gallium scanning, exercise-induced hypoxaemia, DTPA scanning and lung function testing have been developed to improve on the diagnostic value of clinical examination and the chest X-ray. Although each has its own particular advantages and disadvantages, the most efficient means of diagnosing PCP, in patients presenting with respiratory symptoms, is to use these investigations as part of a diagnostic algorithm, thereby maximizing resources and defining relative risks for different types of patients.