Applying a prediction rule to identify low-risk patients with community-acquired pneumonia

Study objectives: To study the validity of a recently developed community-acquired pneumonia (CAP) severity prediction rule in estimating mortality, to determine its utility in decision making regarding hospitalization, and to assess factors influencing this decision. Design: Retrospective chart review. Setting: Two sites of the University Health Network, the Toronto General and Toronto Western Hospitals, tertiary-care teaching institutions with a sizable primary-care and secondary-care source of referrals, and a total of 900 beds. Patients: Consecutive patients with CAP admitted between February and June 1996. Measurements and results: A single trained medical records extractor assembled data to compare our population to that used in developing the CAP prediction rule, in terms of mortality and to assess reasons for hospitalization. Two hundred fifty-five eligible patients were admitted, and 244 charts (96%) were available. Our patients tended to be older, with nearly four times as many residents of chronic care institutions (39% compared with 10%), and had a higher risk class distribution than the published cohort. Risk class-specific mortality was similar in four of five classes. Of the 71 patients in the low-risk classes, 67 had additional reasons for admission; 18 of which were psychosocial (homelessness, substance abuse, or inadequate home supports). Conclusions: The CAP severity prediction rule estimates mortality well. Admission of low-risk patients was linked to psychosocial and other medical reasons not captured by this rule. The rule can be very useful in assessing the need for hospitalization; however, there remains a significant percentage of patients with a low severity score who may require hospitalization for psychosocial and economic considerations.