Oxygen Saturation or breathlessness? How best to predict pneumonia in patients presenting with a cough to primary care

SYNOPSISO_ST_ABSBackgroundC_ST_ABSDistinguishing pneumonia from acute bronchitis has an important bearing on treatment decisions. The best validated diagnostic decision rule was derived from the GRACE-09 study. The 3Cs study provides oxygen saturations in addition to clinical signs and symptoms. Oxygen saturation is a predictor in hospital settings and may be beneficial in primary care. ObjectivesThis project evaluates whether the data from GRACE-09 and 3Cs studies can be mapped onto each other and be combined dataset to refine the diagnostic accuracy of the GRACE-09 clinical prediction rule for the diagnosis of pneumonia. Patients and MethodsGRACE-09 included 3106 patients with acute cough in a multicentre European study. 3Cs is a UK based study of 28883 patients with acute cough. Binary logistic regression was used in the 3Cs dataset to determine which variables significantly predicted low oxygen saturation (<95%). Statistically significant predictors were determined using area under curve (AUC). This equation was used to model the probability of low oxygen saturation in the GRACE-09 dataset and subsequently included in the GRACE-09 model to determine whether low oxygen saturation is a comparable predictor to breathlessness in predicting pneumonia. ResultsFor 3Cs, using all seven variables achieved an AUC for low oxygen saturation of 0.73 (95% CI 0.72-0.74). Substituting low oxygen saturation into GRACE-09 model gives AUC 0.75 (95% CI 0.69-0.82) compared to original GRACE-09 using breathlessness and gives AUC 0.77 (95% CI 0.73-0.82). ConclusionsLow oxygen saturation and breathlessness are similarly predictive and could be used interchangeably in a modified GRACE-09 prediction model. KEY MESSAGESCan pulse oximetry replace subjective breathlessness assessment in the GRACE-09 prediction rule? Pulse oximetry gives an objective measurement that can be used to assist the diagnosis of pneumonia in primary care.