Risk stratification for patients with community-acquired pneumonia.
You will note that this was derived prior to the concept of healthcare-associated pneumonia (HCAP), and so living in a nursing home is a criterion for this rule.
Fine MJ et al. A prediction rule to identify low-risk patients with community-acquired pneumonia. N Engl J Med. 1997; 336(4):243-50.
Aujesky D et al. Prospective comparison of three validated prediction rules for prognosis in community-acquired pneumonia. Am J Med. 2005; 118(4):384-92.