- Assess Krebs von den Lungen-6 (KL-6) and Calprotectin as novel biomarkers for diagnosis of ILD among Rheumatoid arthritis patients

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by small joint synovitis that is estimated to affect 0.3% to 1% of the global population. Extraarticular disease may occur in up to 50% of patients with RA, with pulmonary manifestations among the most common extraarticular features. Interstitial lung disease (ILD) clinically affects up to 10% of patients with RA and subclinically affects up to 40%.

RA-ILD typically presents as a usual interstitial pneumonia (UIP) or nonspecific interstitial pneumonia pattern. Diagnosis requires a thorough evaluation, including laboratory and imaging studies; pulmonary function testing (PFT); medication review; occasionally, tissue histopathology; and frequently, multidisciplinary input.

Prompt recognition of RA-ILD is crucial because it warrants close monitoring and often necessitates therapeutic alterations.

Biomarkers are a promising area of investigation in RA-ILD because they have the potential to advance pathophysiologic understanding and elucidate therapeutic targets, improve disease identification and diagnostic accuracy, facilitate prognostication, and inform treatment decisions. Although imaging and histopathology have important roles that are unlikely to be replaced by biomarkers, they can be nonspecific in RA-ILD, can be impractical to obtain in certain settings, and cannot be scaled for population health efforts.

Calprotectin belongs to the S-100 proteins produced by neutrophils, which likely contribute to idiopathic pulmonary fibrosis (IPF) pathogenesis. Calprotectin is a well-established biomarker in inflammatory bowel diseases.

Inclusion Criteria:

• Confirmed diagnosis of Rheumatoid arthritis, age > 18 years.

Exclusion Criteria:

• Patients who refuse to participate in the study,
• Patients with evidence of worsening or exacerbation of RA over the previous 6 months,
• concomitant diagnosis of an active neoplasia, or
• patients who had previously received radiotherapy,
• End organ failure.

Confirmed diagnosis of Rheumatoid arthritis, age > 18 years and confirmed diagnosis of ILD based on HRCT findings and Pulmonary function test results.