FEF25-75의 Mannitol 기도 유발 검사에 대한 예측도 분석

Abstract

Abstract Background Bronchial hyperresponsiveness (BHR) is a pathophysiologic feature of asthma and can be evaluated by means of bronchial provocation test. Reduced forced expiratory flow between 25% and 75% of vital capacity (FEF25-75) has been suggested as early marker for small airway obstruction. Mannitol is a pharmacologic agonist, which most commonly used in indirect bronchial provocation test. But the correlation between small airway dysfunction and BHR to mannitol has not been studied. The aim of this study is to determine whether FEF25-75 as a surrogate measure of small airways function is associated with BHR to mannitol. Methods We compared the baseline FEF25-75 (presented as percent of predicted value) with the other spirometric parameters including forced expiratory volume in 1 second (FEV1) percent predicted, forced vital capacity (FVC) percent predicted and ratio of FEV1 to FVC (FEV1/FVC). And all 428 patients performed mannitol bronchial provocation test. The cumulative mannitol dose that caused a 15% decrease in the FEV1 from baseline was defined as PD15 and dose was limited to 635mg. In area under the receiver operating characteristic curve (AUC) for predicting BHR, percent of predicted value of FEF25-75 was compared with FEV1, FEF25-75/FVC and FEV1/FVC. Statistical analyses were carried out using the AUC with comparisons using the DeLong method. Results In all patients, rate of BHR to mannitol was 20.3 percent. Comparing spirometry parameters, percent of predicted value of FEF25-75 (62.4%; P<0.001) had significant low than other parameters, such as percent predicted value of FEV1 (84.1%; P<0.001), FVC (94.4%; P=0.048) and FEV1/FVC (75.1%; P<0.001). AUC analysis showed that percent of predicted value of FEF25-75 (0.772; 95% confidence interval [CI], 0.729-0.811) had significantly higher than percent of predicted value of FEV1 (0.666; 95% CI, 0.619-0.710; P< 0.001), FEF25-75/FVC (0.741; 95% CI, 0.696-0.782; P= 0.045) and FEV1/FVC (0.741; 95% CI, 0.697-0.782; P = 0.046). Similar results were obtained after excluding subjects with lower than 80 percent of predicted value of FEV1 or less than 70 percent of FEV1/FVC. In other words, comparing with normal spirometry, percent of predicted value of FEF25-75 (0.704; 95% CI, 0.646-0.757) had significantly higher AUC value than percent of predicted value of FEV1 (0.589; 95% CI, 0.529-0.648; P= 0.011), FEF25-75/FVC (0.665; 95% CI, 0.606-0.720; P= 0.2313) and FEV1/FVC (0.644; 95% CI, 0.584-0.700; P = 0.047). Conclusion FEF25-75 showed significantly better association with responsiveness to mannitol compared to the other spirometric parameters even in the patients with a normal spirometry, suggesting that small airway dysfunction could be a sign of BHR.