Community-acquired pneumonia (CAP) is defined as an acute infection of the pulmonary parenchyma in a patient who has acquired the infection in the community, as distinguished from hospital-acquired (nosocomial) pneumonia. A third category of pneumonia, designated "healthcare-associated pneumonia," is acquired in other healthcare facilities such as nursing homes, dialysis centers, and outpatient clinics or within 90 days of discharge from an acute or chronic care facility . (See "Epidemiology, pathogenesis, microbiology, and diagnosis of hospital-acquired, ventilator-associated, and healthcare-associated pneumonia in adults".)
CAP is a common and potentially serious illness. It is associated with considerable morbidity and mortality, particularly in elderly patients and those with significant comorbidities . (See "Prognosis of community-acquired pneumonia in adults".)
The diagnostic approach to CAP in immunocompetent adults will be reviewed here. A variety of other important issues related to CAP are discussed separately. These include:
The approach to the patient with community-acquired pneumonia (CAP) begins with the clinical evaluation followed by chest radiograph with or without microbiologic testing. A systematic review highlighted the lack of sensitivity of the clinical criteria for an accurate diagnosis of CAP; even a combination of symptoms (cough) and signs (fever, tachycardia, and crackles) did not have a sensitivity above 50 percent when using chest x-ray as the standard .