*The decision to hospitalize a patient with CAP must take into consideration diminishing health care resources and rising costs of treatment. The cost of inpatient management exceeds that of outpatient treatment by a factor of 20 and accounts for most CAP-related expenditures.
*Certain patients clearly can be managed at home, and others clearly require treatment in the hospital, but the choice is sometimes difficult. Tools that objectively assess the risk of adverse outcomes, including severe illness and death, may minimize unnecessary hospital admissions and help to identify patients who will benefit from hospital care.
*There are currently two sets of criteria: the Pneumonia Severity Index (PSI), a prognostic model used to identify patients at low risk of dying; and the CURB-65 criteria, a severity-of-illness score.
*To determine the PSI, points are given for 20 variables, including age, coexisting illness, and abnormal physical and laboratory findings.
*On the basis of the resulting score, patients are assigned to one of five classes with the following mortality rates:
-class 1, 0.1%;
-class 2, 0.6%;
-class 3, 2.8%;
-class 4, 8.2%; and
-class 5, 29.2%.
*Clinical trials have demonstrated that routine use of the PSI results in lower admission rates for class 1 and class 2 patients. Patients in classes 4 and 5 should be admitted to the hospital, while those in class 3 should ideally be admitted to an observation unit until a further decision can be made.
*The CURB-65 criteria include five variables:
1. Confusion (C);
2. Urea >7 mmol/L (U);
3. Respiratory rate greater than or equal to 30/min (R);
4. Blood pressure, systolic less than or equal to 90 mmHg or diastolic less than or equal to 60 mmHg (B); and
5. Age greater than or equal to 65 years (65).
*Patients with a score of 0, among whom the 30-day mortality rate is 1.5%, can be treated outside the hospital.
*With a score of 2, the 30-day mortality rate is 9.2%, and patients should be admitted to the hospital.
*Among patients with scores of greater than or equal to 3, mortality rates are 22% overall; these patients may require admission to an ICU.
*At present, it is difficult to say which assessment tool is superior. The PSI is less practical in a busy emergency-room setting because of the need to assess 20 variables. While the CURB-65 criteria are easily remembered, they have not been studied as extensively. Whichever system is used, these objective criteria must always be tempered by careful consideration of factors relevant to individual patients, including the ability to comply reliably with an oral antibiotic regimen and the resources available to the patient outside the hospital.