Severity prediction rules in community acquired pneumonia: a validation study

Background-The British Thoracic Society (BTS) developed a rule (BTSr) based on severity criteria to predict short term mortality in adults admitted to hospital with community acquired pneumonia (CAF). However, neither the BTS r nor a recent modification of it (mBTSr) have been validated in the UK. A case-control study was conducted in a typical UK population to determine th e clinical factors predictive of mortality and to assess the performance of these rules. Methods-Cases were drawn from all patients with CAP who died in 1997 in fiv e large hospitals in the Mid Trent area. Controls were randomly selected fr om survivors. Factors associated with mortality were identified following r eview of medical case notes and performance of the severity prediction rule s assessed, Results-Age >65 years, temperature <37 degrees C, respiratory rate >24 brea ths/min, mental confusion, urea concentration of >7 mmol/l, sodium concentr ation of <135 mmol/l, and the presence of a pleural effusion, all determine d on admission, were independently associated with in-hospital mortality on multivariate analysis. The BTSr was 52% sensitive and 79% specific in pred icting death while the mBTSr displayed 66% sensitivity and 73% specificity. Conclusions-The value of three of the four factors (presence of mental conf usion, raised respiratory rate, raised urea) used in the mBTSr as predictor s of mortality is confirmed. However, the BTSr and mBTSr did not perform as well in this validation study which included a high proportion (48%) of el derly patients (greater than or equal to 75 years) compared with the deriva tion studies.