Fixed airways obstruction among patients with severe asthma: findings from the Singapore General Hospital-Severe Asthma Phenotype Study

Table 3 Variables correlated with postbronchodilator forced expiratory volume in one second % predicted

Variable	Correlation coefficient	p-value
Age (years)	0.203^#	0.08
Age of onset (years)	0.200^#	0.09
Duration of asthma (years)	-0.056^#	0.63
Body mass index (kg/m²)	0.029^#	0.80
Serum eosinophils (× 10⁹/L)	-0.092^#	0.43
Pack-year smoking history	-0.306*	0.007
Asthma control test score	0.143*	0.22
No. of emergency visits in past two years	0.102*	0.39
Steroid bursts in the past year	0.102*	0.38
Medication regimen	0.014*	0.90
Admissions in the past year	0.278*	0.015
Prebronchodilator FEV₁ (% predicted)	0.882^#	<0.001
Prebronchodilator FVC (% predicted)	0.650^#	<0.001
Prebronchodilator FEV₁/FVC (%)	0.425^#	<0.001
Reversibility (%)	0.012^#	0.92
Reversibility (ml)	0.163^#	0.16

Medication regimen is expressed as an ordinal scale as follows: 1 = inhaled corticosteroid only, 2 = combination inhaled corticosteroid and beta-agonist (Combi), 3 = Combi + theophylline, 4 = Combi + leukotriene receptor antagonist (LTRA), 5 = Combi + Theophylline + LTRA, 6 = Long term steroids, 7 = Omalizumab, 8 = Anticholinergic, 9 = All of the above.
^#Pearson coefficients, *Spearmann coefficients. FEV₁ = forced expiratory volume in one second, FVC = forced vital capacity.

ISSN: 1471-2466