In addition to pulmonary function testing, anti–Scl-70 antibody testing and high-resolution CT (HRCT) would be most helpful in establishing a diagnosis. In this particular patient, there are findings of skin thickening in the distal extremities, which suggests diffuse cutaneous systemic sclerosis (dcSSc). Patients with dcSSc are more likely to develop diffuse parenchymal lung disease (DPLD), serositis, and kidney disease (including scleroderma renal crisis). DPLD most commonly occurs in patients with dcSSc and elevated antibody titers to anti–Scl-70. Alveolitis may precede the development of DPLD; presenting manifestations include dyspnea, nonproductive cough, and exercise intolerance. Fine bibasilar Velcro-like inspiratory crackles are frequently present on physical examination. A restrictive impairment with decreased lung volumes and decreased DLCO is typically present on pulmonary function tests. Chest imaging is best performed with HRCT, which is more sensitive than plain radiography in detecting alveolitis and reticular linear opacities present in patients with early stages of lung disease. As a result, anti–Scl-70 antibody testing and HRCT scan are most likely to establish the diagnosis.

Complete pulmonary function testing (spirometry, lung volumes, and diffusing capacity) is an important component of evaluating parenchymal lung disease. It can assess the severity of disease, and the discovery of different patterns can confirm the presence of restrictive lung diseases, such as DPLD, or the presence of obstructive or mixed patterns that can help further focus the differential diagnosis. The finding of a low diffusing capacity that is out of proportion to the decrease in lung volumes suggests the presence of other conditions such as pulmonary hypertension.

Anti–PM-Scl antibody is associated with myositis. Anticentromere antibody is associated with limited cutaneous systemic sclerosis and the risk of developing pulmonary hypertension. Antineutrophil cytoplasmic antibody is associated with granulomatosis with polyangiitis, microscopic polyangiitis, and eosinophilic granulomatosis with polyangiitis (formerly known as Churg-Strauss syndrome); it is not associated with systemic sclerosis.

Bronchoalveolar lavage, lung biopsy, and gallium-67 scanning are generally not helpful in the diagnosis of systemic sclerosis–associated DPLD and would not be performed prior to HRCT scanning.