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Clinical Decisionmaking

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Chest x-ray is appropriate to confirm suspected pneumonia in most patients

Prompt diagnosis of community-acquired pneumonia (CAP) is important to determine the need for antibiotic therapy, and prognosis (risk of death) is important for deciding whether or not to hospitalize the patient. Only 5 percent of patients suspected of having CAP actually do, and findings from the medical history (for example, a cough) and physical examination rarely distinguish CAP from other types of respiratory infections.

Thus, a chest x-ray is needed to confirm the diagnosis in most patients treated for CAP, according to a study performed by Joshua P. Metlay, M.D., Ph.D., of the University of Pennsylvania School of Medicine and VA Philadelphia Medical Center, and Michael J. Fine, M.D., M.Sc., of the University of Pittsburgh and the VA Pittsburgh Healthcare System. This work is an extension of the Pneumonia Patient Outcomes Research Team(PORT), which was supported by the Agency for Healthcare Research and Quality (HS06468).

Normal vital signs such as heart rate, temperature, and respiratory rate significantly reduce the likelihood of CAP. If the patient has only mildly severe illness and no clinical or pharmacologic factors that would modify the presence of abnormalities in vital signs, CAP may be excluded without chest x-ray. Patients with moderate to severe illness and no findings on initial chest x-ray may benefit from antibiotic therapy and repeated chest x-ray after several days to confirm or rule out the diagnosis of CAP.

Overall, individual clinical and laboratory abnormalities are associated with only moderate increases in the odds of death. Thus, a combination of medical history, physical exam, and laboratory tests is needed to accurately assess short-term risk of death and guide decisions about hospital versus home care. This involves identifying absolute contraindications to home care, including deficient arterial oxygen and social and psychological problems, conclude Drs. Metlay and Fine.

The researchers updated two previous literature reviews on the diagnosis and prognosis of CAP by reviewing additional studies conducted from January 1996 through December 2000. They performed a meta-analysis of studies on the ability of the medical history, physical examination, and laboratory findings to diagnose CAP and predict short-term risk of death.

More details are in "Testing strategies in the initial management of patients with community-acquired pneumonia," by Drs. Metlay and Fine, in the January 21, 2003, Annals of Internal Medicine 138(2), pp. 109-118.

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