Clinical importance of the positivity criterion used in the bronchodilation test in spirometry

Aim: To evaluate whether the use of the new positivity criterion for the bronchodilation test (≥ 10% of the reference value) represents a change in the diagnosis with respect to the old criterion (≥ 12% change with respect to the baseline value and more than 200 ml of difference). Method: Retrospective pilot study carried out as a prior step to the complete evaluation of all spirometry performed in the last year at our health center. The spirometry tests with bronchodilation tests performed in our center in the last year on patients over 40 years of age, smokers of more than 10 pack-years, as part of a COPD screening program were taken as a sample. The positivity of the bronchodilation test was analyzed with the old criteria and with the new criteria, and the type of change that occurred was evaluated (no change, previously positive and now negative, previously negative and now positive). Results: 144 valid spirometries were obtained (they met acceptability and reproducibility criteria), corresponding to 144 patients (90 men and 54 women). The average age was 50.3 years ( 7.89), being 51.0  8.45 in men and 49.3 6.80 in women. Of the 144 spirometries, 16 (11.1%) were obstructive. With the old criteria, the bronchodilation test was positive in 4 spirometries (2.7%), and with the new criteria, in 11 (7.6%). Of the 11 positive spirometries according to the new criteria, 5 were initially obstructive and 6 were non-obstructive. 7 spirometry tests went from negative to positive with the new criteria, of which 3 were initially obstructive. Conclusions: Although numerically the impact seems small, the new criteria detect more positive bronchodilation tests than the old criteria, which may be important in the diagnosis and classification of the patients studied.