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

Table 5 Receiver operator curve validation of multivariable models predicting the presence of specific PFT abnormalities

Characteristics included in model	Full cohort (n = 159)			Cohort excluding reported lung disease (n = 129)
	AUC	95% CI^a	P value	AUC	95% CI^a	P value
Model predicting restriction
Pulmonary symptoms only	0.66	(0.51 to 0.81)	-	0.63	(0.51 to 0.80)	-
Symptoms + other factors^b	0.79	(0.59 to 0.92)	0.046*	0.79	(0.61 to 0.92)	0.040*
Model predicting obstruction
Pulmonary symptoms only	0.62	(0.50 to 0.74)	-	0.62	(0.51 to 0.75)	-
Symptoms + other factors^c	0.91	(0.78 to 0.98)	0.0001*	0.86	(0.75 to 0.94)	0.0005*
Symptoms + factors + lung disease	0.96	(0.91 to 0.99)	0.080**	-	-	-
Model predicting impaired diffusion
Pulmonary symptoms only	0.66	(0.58 to 0.73)	-	0.66	(0.57 to 0.75)	-
Symptoms + other factors^d	0.85	(0.75 to 0.93)	0.0003*	0.85	(0.73 to 0.93)	0.001
Symptoms + factors + lung disease	0.86	(0.74 to 0.94)	0.41**	-	-	-

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. ^bOther factors included were those from the final predictive multivariable model (body mass index and current prednisone use). ^cOther factors included were those from the final predictive multivariable model (gender, exercise, current smoking, body mass index, presence of rheumatoid factor, and current prednisone use). ^dOther factors included were those from the final predictive multivariable model (age, current smoking, body mass index, and current prednisone use). *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