[Baseline spirometry parameters that can influence the bronchodilation test]

To determine whether the baseline parameters of forced spirometry can influence the positivity of the bronchodilation test (BDT), and whether this could have an influence in future positivity criteria.

A descriptive, cross-sectional study was conducted in a Primary Care setting. It included all patients referred by their family doctor to perform a forced spirometry test due to smoking, respiratory symptoms, or follow-up of respiratory diseases, between the months of June 2015 and February 2017. All of them were subjected to a forced spirometry with a BDT.

A total of 295 patients were included, with a mean age 53.4±15.5 years, and 62% were male.An obstructive pattern was obtained in 20% of the spirometries, with 67.5% presenting with a mild obstruction, 18% a moderate, 9.6% moderate to severe, and 4.8% very severe. The BDT was positive in 8.8% of the spirometries, with 11.2% only positive in volume, and 17.6% were only positive in percentage. It was observed that the patients with a BDT positive in percentage had a lower base forced expiry volume in the first second (1.66 L/sec vs. 2.74 L/sec; P<.001), and a lower forced vital capacity (2.85 l vs.3.73 l; P<.001). The patients with a positive BDT in volume had a lower forced expiry volume in the first second (2.59 l/sec vs. 2. 62 l/sec; P<.001), and a higher forced vital capacity (3.89 l vs. 3.58 l; P<.001).

The baseline forced expiry volume in the first second and forced vital capacity have an influence in the positivity of the BDT. This circumstance should be assessed when establishing the positivity of the BDT.