Patients with newly diagnosed systemic sclerosis should have a high-resolution lung CT and pulmonary function tests, because when assessed together, their findings identify patients at high risk of interstitial lung disease, researchers say.
In a study of 305 patients with systemic sclerosis (SSc), a baseline high-resolution lung CT showing no fibrosis was highly predictive of a fibrosis free follow-up scan at 3 years, reported the researchers from Oslo (Norway) University Hospital. SSc associated interstitial lung–disease (SSc-ILD) typically has an insidious onset with subtle clinical symptoms, accoording to the authors in background information to the paper published in Arthritis & Rheumatology (Arthritis & Rheumatology 2015; [doi:10.1002/art.39166]).
This may explain why SSc-ILD is often diagnosed at an advanced stage, when extensive lung fibrosis is already present. “Better, and more targeted, strategies for SSc-ILD identification and risk stratification early in the disease course are therefore warranted,” they wrote.
In order to assess serial lung fibrosis measurements and paired pulmonary function tests (PFTs) as outcome prediction tools, the researchers prospectively analyzed both modalities at baseline and at an average of 3 years follow-up in 305 patients with SSc. The extent of fibrosis was scored on 10 sections from every high-resolution CT (HRCT) and expressed as a percentage of total lung volumes.
The researchers identified three groups of patients: More than 20% lung fibrosis (n=40), between 1%- 20% fibrosis (n=157), and no fibrosis (n=108). Results showed that all 108 patients who had no lung fibrosis at baseline remained free of fibrosis at a 3-year follow-up scan. These patients were predominantly female (88%) had limited (lc) SSc (84%), and were positive for anticentromere antibodies (ACA) (70%). They also had a high baseline decline in diffusing lung capacity for carbon monoxide (DLCO) that declined by 8.2%, the same degree as patients with lung fibrosis.
“This finding emphasizes that the mechanics behind SSc related DCLO changes probably are multifactorial and may involve pathology in the vasculature,” the study authors wrote. This was underscored by the observation that pulmonary hypertension (PH) was present in all groups of patients and supported the notion that PH screening should be conducted independently of fibrosis screening, the researchers noted.
For patients in the 1%-20% group, 146 were the same at follow-up, whereas the remaining patients progressed to more than 20% fibrosis. These 11 patients were characterized by significantly shorter average disease duration at baseline (1.3 years) compared with the other groups.
The 40 patients with more than 20% fibrosis at baseline had a higher annual fibrosis progression rate (aFPR), declining PFT values, and development of pulmonary hypertension (PH). Most of this group had diffuse SSc (55%), were positive for anti-topoisomerase antiboidies (ATA) (48%), and had a higher frequency of PH (28%), the researchers said. The rate of annual fibrosis progression differed across all groups and correlated with total FVC decline.
Surprisingly, neither baseline fibrosis nor annual fibrosis progression significantly predicted mortality. This finding may be partly due to survival bias in the cohort and the statistical power of the study, the researchers said. “The results indicate that a baseline examination in newly diagnosed SSc patients should include lung HRCT and PFTs,” the researchers concluded. Patients with low ILD risk should not undergo serial HCRT examination but probably need serial PFTs as an adjunct PH detection tool, they said.