Serum study may be helpful in the diagnosis of Caplan Syndrome. Serum study may found positive for rheumatoid factor, antinuclear antibodies, elevated ESR, and CRP.

Serum study may be helpful in the diagnosis of Caplan Syndrome. Findings might include:

• positive Rheumatoid factor
• positive antinuclear antibodies
• elevated ESR and CRP

• Lung function tests may reveal a mixed restrictive and obstructive ventilatory defect with a loss of lung volume. There may also be irreversible airflow limitation and a reduced gas transfer factor.
• Silicosis and asbestosis must be considered in the differential with TB.^{[1] [2]}