Revision of the severity rating and classification of hospital-acquired pneumonia in the Japanese Respiratory Society guidelines

Background and objective: Based on the results of a multicentre collaborative survey of hospital-acquired pneumonia (HAP) conducted in Japan, the severity rating and classification of pneumonia in the Japanese Respiratory Society guidelines for management of HAP were examined. Methods: Parameters for the severity classification were selected from the factors associated with prognosis in the HAP survey and in other previous reports. Depending on the presence of the parameters listed below, patients with HAP were stratified into those with high, moderate or low-risk. The high-risk group was defined as patients with three or more of the following risk factors: 'malignant tumour or immunocompromised status', 'impaired consciousness', 'requiring fraction of inspired oxygen (FiO₂) >35% to maintain SaO₂ >90%', 'man aged 70 years or older, or woman aged 75 years or older' and 'oliguria or dehydration.' The moderate-risk group was defined as patients with any of the secondary risk factors as follows: 'CRP ≥ 200 mg/L' and 'extent of infiltration on CXR covers at least 2/3 of one lung'. The low-risk group was defined as all other patients. Results: Application of this classification scheme to the patients enrolled in the HAP survey revealed a mortality rate of 40.8% (98/240) in the high-risk group, which was significantly higher than the mortality rates in the moderate and low-risk groups: 24.9% (69/277) and 12.1% (101/834), respectively. Conclusion: These results indicate that it is possible to classify patients using these parameters as prognostic indicators.