Reliability of Peak Expiratory Flow Measurement in Assessing Bronchodilator Response of Airflow Obstruction

Abstract

Turkish national guidelines recommend peak expiratory flow (PEF) measurements for assessing the reversibility of airflow obstruction in the primary care setting because it is cost-effective and practical. In this study, the usefulness and reliability of PEF as an alternative parameter to forced expiratory volume in 1 second (FEV1) as a reversibility test was investigated. Eighty-three subjects with asthma symptoms and airflow obstruction on spirometry met inclusion criteria. The mean age of the subjects was 42 ± 17.5 years; 52% were men. The FEV1% was between 53% and 80% in the study population. PEF was assessed using a manual peak flow meter, while FEV1 was obtained from the spirographic curve. A positive bronchodilator response was defined as an increase in FEV1 of >12% predicted after inhaling 400 µg of salbutamol. This response was compared with an increase in PEF% from baseline with cutoff values of 15% and 20%. FEV1 >12%, PEF >15%, and PEF >20% bronchodilator response was observed in 59%, 61%, and 49% of patients, respectively. There was a weak correlation between postbronchodilator FEV1 and PEF increase ( r = 0.275, P = .012). An increase in PEF >15% showed a sensitivity of 74%, specificity of 58%, positive predictive value (PPV) of 74%, and negative predictive value (NPV) of 59% compared with an FEV1 response of >12%. Similarly, an increase of PEF >20% had a sensitivity of 54%, specificity of 57%, PPV of 65%, and NPV of 45%. The clinical value of PEF measurements in the diagnosis of reversible obstructive airway disease was less reliable than FEV1. Therefore, it should be reevaluated for widespread usage.