Relationship Between FEV1& PEF in Patients with Obstructive Airway Diseases

Abstract

ABSTRACT:BACKGROUND:Spirometry is the recommended investigation for diagnosis and categorization of the severity of the air flow limitation, however Spirometer is not widely available, while Peak-flow meter is cheap, portable, and easy to operate and maintain, so the PEF is frequently proposed as alternative to FEV1 for this purpose, and widely used in general practice as a surrogate for FEV1 in assessment of airway obstruction diseases.OBJECTIVE:To determine effect of FEV1 & PEF in obstructive airway diseases.PATIENTS AND METHODS:This study was took place between 1st December 2006 and 1st July 2007in Baghdad teaching hospital. A total of 100 patients with history suggestive of obstructive airway diseases (symptoms of cough, wheezes, shortness of breath, and chest tightness), and their pulmonary function test show obstructive pattern (FEV1/FVC <70%) were included. They were (60%) male and (40%) female, and their age ranged from 16 to 82 years.RESULTS:In screening for obstructive airway diseases, there was a significant relationship (P value <0.05) between FEV1% and PEF%, (94%) of patients with obstructive airway disease as assessed byFEV1% (FEV1 %< 80%) had PEF %< 80%.In severity categorization, the PEF% and FEV1% were concordant in only (60%) of patients, with better concordance as severity of obstruction (based on FEV1%) became more. In patients with mild to moderate airway obstruction (FEV1%>40%), PEF% tended to underestimate FEV1%; while in patients with more severe obstruction (FEV1 %< =40%), PEF% tended to overestimate FEV1%. For the entire study population, PEF% underestimated FEV1% by mean of only 0.35%. However, limits of agreement were wide and exceeded-/+ 14.5. In our study 70% of patients had discordance more than 5% apart between PEF% and FEV1%, (which could be considered clinically important error for estimation of severity of airway obstruction), and this discordance more marked in women, short patients, and in patients with mild airway obstruction.CONCLUSION:The PEF% can reliably exclude airway obstruction, when normal value is present. Assumption of parity between PEF% and FEV1% must be avoided especially in categorization of severity of air way obstruction