A novel risk score helps identify interstitial lung disease in patients with systemic sclerosis

Although patients with systemic sclerosis-related interstitial lung disease (SSc-ILD) present with characteristic changes in high-resolution computed tomography (HRCT), a considerable percentage do not undergo imaging, especially during follow-up visits. Therefore, researchers developed a score to enable physicians to identify at-risk patients.

ILD is identified in most patients with SSc and is the leading cause of SSc-related mortality [1]. HRCT is the gold standard for diagnosis. However, some physicians do not regularly perform baseline HRCTs in all patients. “Our previous survey identified that only about 66% of physicians regularly screen for ILD with HRCT at the time of SSc diagnosis, and this percentage drastically drops to less than 15% during follow-up visits,” explained Dr Cosimo Bruni (University of Zürich, Switzerland) [2]. Therefore, Dr Bruni and his research group aimed to develop a risk score for the presence of SSc-ILD (the ILD-RISC score) to guide physicians in ordering both baseline and follow-up HRCTs.

For the identification of SSc-ILD, 13 variables were considered important: sex, age, disease duration from first non-Raynaud’s phenomenon sign or symptom, skin subset, presence of oesophageal symptoms, current or past digital ulcers, arthritis, smoking, increased inflammatory markers, New York Heart Association (NYHA) class, positive SSc-related autoantibodies, the percentage of forced vital capacity (FVC%), and the percentage of diffusing capacity for carbon monoxide (DLCO%).

The prediction model for ILD was developed from baseline visits of SSc patients in 6 European referral centres using multivariable logistic regression with backward selection. Of the 780 included patients, 533 (43% ILD) and 247 (48% ILD) were randomly assigned to the derivation and validation cohorts.

In the derivation cohort, a model including FVC%, DLCO%, digital ulcers, age, and SSc-related autoantibodies showed an OR of 133.9 (95% CI 53.4-335.9) for the presence of ILD on HRCT. An ILD-RISC score ≥0.3 showed comparable precision and accuracy in the derivation, validation, and longitudinal cohorts, with a sensitivity of 85.6% and specificity of 53.6%.

Among 819 patients with negative baseline HRCT, 170 (20.8%) developed ILD during a 3.8 ± 3.0 years follow-up. Longitudinally, in almost 50% of visits (n=914/1809), HRCT could be correctly skipped following an ILD-RISC score <0.3.

“We still recommend performing HRCT screening in all patients if the test is readily available and patients are willing to undergo it so as not to miss any patient with ILD. However, in situations where HRCT is unavailable, our ILD-RISC score supports the ability of HRCT to identify this complication. Most important, it may help to decide when to order HRCTs at follow-up, thus limiting unnecessary exams,” Dr Bruni explained.

A limitation of the score is its relatively low specificity, leading to a certain number of false positives.

“We are already working to improve the score further and continue to reduce the number of unnecessary HRCTs,” he concluded.

1. 
   
   1. Fischer A, et al. Open Access Rheumatol. 2019;11:283-307.
   2. Bruni M, et al. Developing a screening tool for the detection of interstitial lung disease in systemic sclerosis: the ILD-RISC risk score. 1526, ACR Convergence 2022, 10–14 November, Philadelphia, USA.

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Posted on 1 December, 20221 December, 2022