SPAR Model May Predict Mild Interstitial Lung Disease in Systemic Sclerosis

chest xray
chest xray
The SPAR prediction model might be helpful for the risk stratification of mild ILD in patients with SSc in clinical practice.

The evidence-based SPAR prediction model may be beneficial for the risk assessment of mild interstitial lung disease (ILD) in patients with mild systemic sclerosis (SSc), according to the results of an observational study published in the Annals of the Rheumatic Diseases.

The investigators sought to identify the prognostic clinical features and to establish a model for predicting progression of mild ILD in patients with SSc. All patients from 2 independent prospective cohorts met 2013 American College of Rheumatology/European League Against Rheumatism criteria, had mild ILD at baseline, had available baseline and ≥1 annual follow-up pulmonary function tests, and did not have concomitant airflow obstruction or pulmonary hypertension. The prediction model for progression of ILD was established in a derivation cohort and was then confirmed in a validation cohort.

Progression of ILD was defined as a relative decrease in forced vital capacity ≥15% or relative decrease in forced vital capacity ≥10% combined with diffusing capacity for carbon monoxide ≥15% at the 1-year follow-up.

Overall, 25 of 98 participants with SSc from the derivation cohort and 25 of 117 participants with SSc from the validation cohort demonstrated progression of ILD. In both cohorts, lower oxygen saturation, measured by pulse oximetry (SpO2) after a 6-minute walk test, and arthritis were both identified as independent predictors for progression of ILD. A receiver operating characteristic curve analysis determined that the optimal cut-off value of SpO2 following a 6-minute walking test was 94% for prediction of ILD progression.

Use of the derived SPAR model that combined both predictors — SpO2 and arthritis —significantly increased the prediction rate from 25.5% to 91.7%, with an area under the curve of 0.83 (95% CI, 0.73-0.93; P <.001) in the derivation cohort and an area under the curve of 0.82 in the validation cohort (95% CI, 0.70-0.94; P <.001).

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The investigators concluded that use of the evidence-based SPAR model might assist physicians in identifying patients with mild SSc-ILD at risk for progressive lung fibrosis, with resultant possible implications for therapeutic strategies in clinical practice.

Please see original article for a full list of disclosures.

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Wu W, Jordan S, Becker MO, et al. Prediction of progression of interstitial lung disease in patients with systemic sclerosis: the SPAR model [published online June 6, 2018]. Ann Rheum Dis. doi: 10.1136/annrheumdis-2018-213201