Fig. 3

Illustration of HAQ-DI transition states (0–0.5, 0.5–1.0, 1.0–1.5, 1.5–2.0, and 2.0–3.0), risk of advanced lung involvement, and death for a patient with dcSSc. HAQ-DI state in t − 1 influences the lung status in t. Similarly, the lung status in t − 1 influences the HAQ-DI state in t. The lung status in t − 1 (which is influenced by the HAQ-DI state in t − 2) influences the mortality in t. t = time in years, and f = “is a function of”. Note: Each HAQ-DI state should be included in a “triangle” as they all influence the lung and no lung states. However, due to lack of space on the diagram, two triangles were omitted. dcSSc diffuse cutaneous systemic sclerosis, HAQ-DI Health Assessment Questionnaire-Disability Index