Influence of Different Spirometry Interpretation Algorithms (SIA) on Decision Making Among Primary Care Physicians

Abstract

PURPOSE: Spirometry is recommended for the diagnosis of asthma and Chronic Obstructive Pulmonary Disease (COPD) in international guidelines and it may be useful for distinguishing asthma from COPD. Typically, the only data required for clinical decision making are the Forced Expiratory Volume in one second (FEV1) and the Forced Vital Capacity (FVC). Limitations of SIA promoted for adoption in primary care have been described [Can Fam Physician October 2011 57:1148- 1152, 1153-1156.] This study examines how different SIA (one and two) may influence decision making among primary care physicians. METHODS: Data for this initiative were gathered from 90 primary care physicians attending standardized accredited (CFPC) workshops in Canada between 2011 and 2013. Physicians were asked to interpret nine spirograms presented twice in random sequence using two different SIA (as stand alone aids) and touch pad technology (remote audience response devices) for anonymous data capture and recording. RESULTS: We observed important differences in the interpretation of spirograms using two different SIA. When the prebronchodilator FEV1/FVC ratio was greater than 0.70, algorithm one lead to a “Normal” interpretation (82% of physicians) while algorithm two prompted a bronchodilator challenge revealing changes in FEV1 that were consistent with asthma; an interpretation selected by 90% of physicians. When the FEV1/FVC ratio was < 0.7 after bronchodilator challenge but FEV1 increased > 12 % and 200 ml, 72% suspected Asthma and 16% suspected COPD using algorithm one while 74% suspected Asthma or COPD using algorithm two. The absence of a post-bronchodilator FEV1/FVC decision node in algorithm one did not permit consideration of possible COPD. CONCLUSIONS: This study suggests that different SIA may influence decision making and lead clinicians to interpret the same spirometry data differently.