[Characteristics and criteria for bronchial responsiveness measurement in cough variant asthma]

To investigate the value of sGaw in the differentiation of CVA from COPD.

MEFV, airway resistance(Raw) and bronchial responsiveness were measured in 30 cases with CVA, 133 cases with typical bronchial asthma(BA) and 37 cases with COPD.

(1) The expiratory-flow parameters (PEF, MMEF, FEV1/FVC) in MEFV curve in remission period of CVA were largely normal, but most patients with CVA (67%) have increased Raw and decreased sGaw, characteristics similar with typical bronchial asthma (BA). (2) If PC35sGaw < 8 g/L was set as the positive limit, 100% of CVA and BA patients showed bronchial hyperresponsiveness(BHR), the average positive MCH concentration being about 1.0 g/L. 5 cases with COPD (13.5%) also showed BHR, but the average MCH concentration was 5.24 g/L. (3) If PC35sGaw < 4 g/L was set as the positive limit for the diagnosis of CVA, the sensitivity was 96.7%, specificity 97.3%, confidence limit 99%. (4) A equation for PC35sGaw was deduced, and its calculation values showed the same results with the ones from diagrammatization.

sGaw is a sensitive index for the measurement of bronchial responsiveness, and it is useful in the differentiation of CVA from COPD. It is suggested that PC35sGaw < 8 g/L be regarded as bronchial hyperresponsiveness, and PC35sGaw < 4 g/L as candidate for CVA.