Mild, stable interstitial lung disease symptoms present in about half of patients with MCTD
About half of patients with mixed connective tissue disorder had abnormal pulmonary function tests and reduced forced vital capacity that remained stable over 10 years of follow-up, according to researchers at the Hospital das Clinicas, University of Sao Paulo, Brazil.
In a retrospective cohort study of 53 patients with mixed connective tissue disorder (MCTD) who were evaluated for 10 years, researchers studied follow-up pulmonary function tests (PFTs) and high-resolution CT (HRCT) images and conducted structured clinical interviews.
Data retrospectively extracted included smoking status, drug interventions, secondary Sjögren’s syndrome, the presence of pulmonary arterial hypertension (PAH), results of the extractable nuclear antigen antibody (ENA) panel, anti-double-stranded DNA (dsDNA), immunoglobulin G (IgG) and IgM anticardiolipin (aCL) autoantibodies, and rheumatoid factor (RF) laboratory tests.
Spirometry plethysmographic lung volume measurements and diffusion capacity for carbon monoxide (DLco) were employed to measure PFT. Within 6 months of the PFTs, HRCT scans were performed at baseline with a single-slice scanner and follow-up images were performed with a multi-slice scanner from the lung apices to the bases without the use of intravenous contrast medium. Scans were each independently reviewed by two chest radiologists blinded to clinical and functional data. The presence of ground-glass opacities, reticulation, honeycombing and bronchiolectasis were considered indicative of interstitial lung disease (ILD).
Seven patients were lost to follow-up, four received a changed diagnosis and three died, leaving 39 patients who completed treatment. All of the 39 patients had PAH at baseline and six underwent right heart catheterization. Dyspnea was present in 19 patients (two severe) and patients were in stable condition at the time of PFT and HRCT evaluation.
Three of the 39 patients were unable to perform the FVC test and forced expiratory volume in 1 second, and six were not able to perform the DLco and total lung capacity tests.
Of the 33 patients who completed the DLco and total lung capacity tests, 17 (51.5%) were observed to have abnormal PFTs at baseline. After 10 years, mean DLco decreased by 15% from 84% to 71%. Slightly reduced FVC was observed in the group at baseline, but FVC remained stable after 10 years on most patients, according to the researchers. Three patients showed decreases in FVC of more than 20%. An obstructive ventilator defect was seen in one patient who was a non-smoker, despite 30% of the cohort classified as former smokers.
A moderate and statistically significant negative correlation was observed between baseline and follow-up FVC with ILD scores derived from HRCT, as well as between follow-up DLco and lower lobe HRCT-derived ILD scores. The 10-year change in DLco moderately correlated with the change in ILD scores derived from the HRCT images, according to the researchers.
Of the seven patients (13%) lost to follow-up, mean follow-up time was 7 years and baseline functional status did not differ from the remaining sample with mean baseline forced vital capacity (FVC) at 72%. - by Shirley Pulawski
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