Combining information from prognostic scoring tools for CAP: an American view on how to get the best of all worlds

Abstract

Prognostic scoring systems for CAP have been developed to address these issues. The two prominent tools for this purpose are the Pneumonia Severity Index (PSI), developed in the USA, and the British Thoracic Society rule, which has recently been modified to the CURB-65 rule (referring to its assessment of: Confusion, elevated blood Urea nitrogen, elevated Respiratory rate, low systolic or diastolic Blood pressure, and age >65 yrs) 1, 3. Although each of the two approaches has been proposed as a tool to guide the site of care decision, neither is ideal by itself, and both can be regarded only as providing decision support information that must be supplemented by clinical assessment and judgment. In fact, the two scoring approaches should be viewed as being complementary, as each has different strengths and weaknesses. The PSI seems to have been developed, and best validated, as a way to identify low mortality risk patients, but the scoring system can occasionally underestimate severity of illness, especially in young patients without comorbid illness 2, 5. This is primarily because the PSI heavily weights age and comorbidity, and does not directly measure CAP-specific disease severity. In contrast, the CURB-65 approach may be ideal for identifying high mortality risk patients with severe illness due to CAP who might otherwise be overlooked without formal assessment of subtle aberrations in key vital signs 3. However, one clear deficiency of the CURB-65 approach is that it does not generally account for comorbid illness, and thus may not be easily applied in older patients who may still have substantial mortality risk, even if a mild form of CAP destabilises a chronic, but compensated, disease process. Thus, both tools offer a valuable assessment of patient illness, but from different perspectives, and each is best at identifying patients at opposite ends of the disease severity spectrum.