OBJECTIVE To develop a decision model to identify SSc-associated interstitial lung disease (ILD) patients who are eligible for watchful waiting at ILD diagnosis.

METHODS One hundred and fifty-one SSc-ILD patients who received medical care at Seoul National University Hospital from 1986 to 2013 were enrolled in this retrospective cohort study. ILD was diagnosed by chest CT. Patients with and without immunosuppressive treatment were compared in terms of characteristics at ILD diagnosis to identify distinguishing variables. After multivariate analysis, a decision model for watchful waiting was formulated. Its validity was assessed by comparing the survival of patients whose management in real practice did and did not accord with the management recommended by the model.

RESULTS The untreated group had better survival than the immunosuppressive treatment group (P = 0.0316, by log-rank test). The untreated group was less likely to have gastrointestinal involvement (P = 0.008) and pulmonary arterial hypertension (PAH), as determined by echocardiography) (P = 0.015) and more likely to have favourable initial forced vital capacity (P = 0.0004), favourable initial lung diffusion capacity for carbon monoxide (P = 0.0002) and a low CT grade (P < 0.001). The final watchful waiting decision model included lack of PAH and limited ILD extent on CT. Application of the model to the cohort revealed that patients who were eligible for watchful waiting (as determined by the model) and underwent this management strategy had better survival than eligible patients who underwent immunosuppressive treatment (P = 0.048, by log-rank test).

CONCLUSION Watchful waiting may be effective for SSc-ILD patients who have minimal pulmonary involvement on CT and lack PAH on echocardiography at baseline.