Establishment of new severity ratings based on analysis of hospital-acquired pneumonia

The Japanese Respiratory Society issued its first guidelines for the management of hospital-acquired pneumonia in adults in 2002. Pathological and severity ratings were investigated based on the results of a national multicenter survey of hospital-acquired pneumonia, and the new severity ratings shown below were established (Fig. II-1). Severity ratings in the 2002 guidelines were based mainly on markers that predicted the effectiveness of antimicrobial treatment. In the current revision, severity is rated using markers that predict the prognosis of patients. Five criteria were established as factors that predict prognosis: malignant tumour or immunocompromised status; decreased level of consciousness; FiO(2) >35% required to maintain SpO(2) >90%; age >or=70 years in men or >or=75 years in women; and oliguria or dehydration. Two criteria were established as factors specifying the severity of the pneumonia itself: CRP >or=200 mg/L and shadows infiltrating more than two-thirds the area of one lung on chest radiography. Patients who satisfy up to two of the five criteria above to predict prognosis are classified in the mild group (Group A) if they do not satisfy either of the two criteria specifying severity of pneumonia, or in the moderate group (Group B) if they satisfy one or both of those two criteria. Patients who satisfy three or fewer of the five criteria to predict prognosis are classified in the severe group (Group C). When the new severity ratings were applied to the results of the national multicenter survey of hospital-acquired pneumonia, the mortality rate was found to be 12.1% (101/834) in the mild group (Group A), 24.9% (69/277) in the moderate group (Group B) and 40.8% (98/240) in the severe group (Group C). Statistically-significant differences were seen between groups, and patient classification may be useful as an indicator of prognosis (Fig. II-2).