Pulmonary function test: its correlation with pulmonary high-resolution computed tomography in patients with rheumatoid arthritis

Abstract

Our objective was to try to evaluate lung affection and to correlate an easier and cheaper method with the high-resolution computed tomography (HRCT) findings in patients with RA. Thirty-six RA patients were selected for HRCT lung scan (twelve patients with altered pulmonary function test (PFT) and 24 with normal PFT). The American Thoracic Society criteria were followed for the pulmonary test. Clinical and laboratory variables were recorded. A statistical analysis was done by Kaplan-Meyer survival curve and ROC curve. When HRCT was evaluated in all patients, only sixteen had an HRCT normal and twenty patients showed some radiologic alteration under HRCT such as: pleural thickness, bronchiectasis, interstitial pattern, micro-nodules pattern, ground-glass opacity, and a reticular pattern. A logistic regression showed that methotrexate use, evolution of the disease (beta 0.018), and FEV1 (beta 0.89) were statistically associated with HRCT alterations. A projection of patients, free from event (HRCT lung scan altered), was obtained through a Kaplan-Meyer analysis, using FEV1 as a predictor over time. The curve shows that in the next 240 months (20 years) nearly 40% of the patients with rheumatoid arthritis will have FEV1 values less than 80% of the normal values predicted for the same age and sex. The FEV1 values have demonstrated a good correlation between PFT and HRCT lung scan. Therefore, they provide an accessible tool for tracking early pulmonary alterations. Methotrexate use and time evolution of the disease have been associated with altered FEV1.