Razi Journal of Medical Sciences

    Background & Aim: The evaluation of correlation between FEV1 and PEFR has always been under investigation. The importance of understanding this correlation is to use PEFR instead of FEV1. The aim of this study is to evaluate the correlation between FEV1(Forced Expiratory Volume in the first second) and PEFR(Peak Expiratory Flow Rate) after respiratory challenge tests in young men suffering from dyspnea. Patients & Method: This is a prospective analytical cross-sectional study conducted in 505 Army Hospital between 2003 and 2004. 143 young men with dyspnea were evaluated. All subjects underwent methacholine or exercise challenge tests properly. All challenge tests were performed under the situations described by ATS(American Thoracic Society). Finally, all adjusted FEV1 and PEFR measures and their falls in comparison to basic measures were determined. Pearson and Spearman correlation coefficients and linear regression were used for analysis. In addition, sensitivity, specificity, positive and negative predictive values, positive and negative likelihood ratio for the detection of a fall of 15-20% in FEV1 in line with a fall of 10-30% in PEFR were calculated and their ROC(Recipient Operator Curve) curves were plotted. Results: FEV1 was not normally distributed but its square was. The correlation between squared FEV1 and PEFR was statistically and clinically significant(p=.000, r=0.75). Its linear regression model was(r2=0.57): 99.42* %PEFR= %FEV12. Falls in PEFR and FEV1 correlated significantly(p=.000, r=0.65), but they were not normally distributed. A fall of 15-20% in PEFR had the best diagnostic value for detection of a fall of 20% in FEV1. However, fall in PEFR was less accurate in the prediction of a 15% fall in FEV1 than a 20% one. Conclusion: It seems that the crude measures of PEFR are more reliable in predicting FEV1, while PEFR falls cannot predict falls in FEV1 as reliably. In addition, changes in PEFR could hardly predict small changes in FEV1.