Clinical phenotypes of sarcoidosis using cluster analysis: a Spanish population-based cohort study

Objective Sarcoidosis is a clinically heterogenous disease. The objective of this study is the identification of clinical phenotypes using cluster analysis. Methods A model-based clustering relaying on 19 clinical variables was performed in a retrospective cohort of 342 sarcoidosis patients, diagnosed and followed-up from 1999 to 2019 in a tertiary hospital at Northern Spain. Chi-square test and ANOVA were used to compare categorical and continuous variables among groups. Two-sample t-tests and the partition of Pearson's chi-square statistic were used in pairwise comparisons. The Wasfi severity score was calculated and compared among clusters. Results Cluster analysis identified five groups: C1 (16.1%), C2 (14.3%), C3 (24.3%), C4 (5.0%), and C5 (40.4%). Lung involvement was predominant, ranging from 55.1% (C2) to 100% (C1 and C4). Extrapulmonary involvement was significantly higher in C2 (96.4%) and C3 (98.0%). A significant lower FEV1 percent predicted was detected in C5 (90.5 +/- 21.8) versus C1 (102.0 +/- 22.9), C3 (102.3 +/- 17.6) and C4 (105.8 +/- 20.8). The cluster 5 had a lower FVC percent predicted (96.6 +/- 18.9) than others, ranging from 108.1 +/- 18.0 (C3) to 111.5 +/- 21.7 (C4). The prescription of systemic glucocorticoids and non-corticosteroid immunosuppressants was higher in the clusters 1, 3 and 5. Chronicity rates were higher in C3 (31.3%) and C5 (32.6%) compared to C1 (9.1%) and C4 (0%), as well as the Wasfi severity score values. Conclusion Five phenotypes with different clinical and prognostic characteristics are proposed in our study. Cluster analysis can be a useful tool for identifying clinical patterns in a disease as heterogeneous as sarcoidosis and optimising its management.