Respiratory symptoms and disease characteristics as predictors of pulmonary function abnormalities in patients with rheumatoid arthritis: an observational cohort study

Table 4 Receiver operator curve validation of multivariable models predicting the presence of any abnormal PFTs

	Full cohort (n = 159)			Cohort excluding reported lung disease (n = 129)
	AUC	95% CI^a	P value	AUC	95% CI^a	P value
Symptoms only^b	0.61	(0.53 to 0.69)	-	0.64	(0.55 to 0.76)	-
Symptoms + other factors^c	0.77	(0.68 to 0.86)	0.0006*	0.79	(0.67 to 0.89)	0.005*
Symptoms + factors + lung disease^d	0.80	(0.71 to 0.87)	0.26**	-	-	-

PFT, pulmonary function test. ^a95% confidence interval (CI) obtained with repeated sampling and calculation of area under the curve (AUC) for 1,000 bootstrap resamples with replacement. ^bSymptoms included were those from the final predictive multivariable model (chronic phlegm and breathlessness with ambulating 100 yards). ^cOther factors included were those from the final predictive multivariable model (current smoking, body mass index, presence of anti-cyclic citrullinated peptide antibodies, and current prednisone use). ^dLung disease includes patient self-report of emphysema, asthma, and rheumatoid lung disease. *P values represent the comparison of AUC functions for the symptoms + other factors model vs. the symptom-only model. **P values represent the comparison of AUC functions for the symptoms + factors + lung disease model vs. the symptoms + factors model.

ISSN: 1478-6362