Reasons for Not Performing or Interrupting the MCT

Pisa Sample: Among the 2,841 survey participants, 2,556 subjects were eligible because subjects > 75 years old (n = 285) were invited to answer the questionnaire only.

Table 1—Reasons for Not Performing or Interrupting the MCT*

Variables Po Delta Pisa
Not performed Refusal 774 (62.4) 763 (54.6)
Inability to perform the test 109 (8.8) 87 (6.2)
Baseline FEV1 < 70% 41 (3.3) 50 (3.6)
Reported cardiac or hypertensive 228 (18.4) 384 (27.5)
or neurologic disorders or recent infectious episodes InterruptedDecrement a 10% in FEV1 39 (3.2) 70 (5.0)
percentage after receiving buffer solution Medical or technical reasons 48 (3.9) 44 (3.1)
Total 1,239 (100) 1,398 (100)

*Data are presented as No. (%).

Among the eligible participants, 1,158 subjects (45%) performed the MCT, while 1,398 subjects did not perform it or interrupted the maneuver (Table 1).

There were significant differences among the two samples. When considering subjects performing MCT, in Po Delta there were a lower prevalence of male gender and of symptoms, a higher prevalence of smokers, and people were younger with a lower FEV1 percentage of predicted. Except for the latter and for gender, the same results were found when considering the subjects not performing or refusing the test (Table 2). Moreover, within each sample, subjects either not performing or refusing the MCT were significantly older, had a lower prevalence of smokers, had a higher prevalence of respiratory symptoms, and had a higher prevalence of female gender with lower mean value of FEV1 percentage of predicted, with respect to those performing MCT (Table 2).

Table 3—Comparison Between BHR Assessed by PD20 and By Dose-Response Curve Slope

hdОto0 ln Slope < 2.21(n = 2,081), % ln Slope a 2.21(n = 679), %
High (< 1 mg of 40.9
methacholine)
Medium (1 to 4.8 mg 7.6{ 54.1t
of methacholine)
Nonresponders 92.4 5.0

*Median PD20, 0.54 mg. tMedian PD20, 1.75 mg. {Median PD20, 3.90 mg.

The use of dose-response curve slope allows to determine a measure for all subjects, avoiding the censoring effect inherent in the provocative dose of methacholine inducing a fall of 20% in FEV1 (PD20).

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