What is an ILD Panel?
An ILD panel is a comprehensive set of serological (blood) tests performed to screen for connective tissue diseases and other autoimmune conditions that may be causing or associated with interstitial lung disease. 1
Core Components of the ILD Panel
The majority of expert panelists recommend routinely testing the following markers in all patients with newly identified ILD 1:
- Antinuclear antibodies (ANA) by immunofluorescence 1, 2
- Rheumatoid factor (RF) 1, 2
- Anti-cyclic citrullinated peptide (anti-CCP) antibodies 1, 2
- C-reactive protein (CRP) 1, 2
- Erythrocyte sedimentation rate (ESR) 1
Extended Myositis Panel Components
When inflammatory myopathy is suspected, additional testing includes 1:
- Muscle enzymes: creatine phosphokinase, myoglobin, and aldolase 1
- Antisynthetase antibodies (Jo-1 and others) 1
- Anti-MDA5 (melanoma differentiation-associated protein 5) 1
- Anti-Mi-2 1
- Anti-NXP2 (nuclear matrix protein 2) 1
- Anti-TIF1-γ (transcriptional intermediary factor 1-γ) 1
- Anti-SRP (signal recognition particle) 1
- Anti-HMGCR (3-hydroxy-3-methylglutaryl-CoA reductase) 1
- Anti-SAE (small ubiquitin-related modifier-activating enzyme) 1
- Anti-U1RNP (U1 ribonucleoprotein) 1
- Anti-PM/Scl75 and anti-PM/Scl100 1
- Anti-Ku 1
Systemic Sclerosis-Specific Testing
If systemic sclerosis (scleroderma) is suspected, additional tests include 1:
- Anti-Scl-70/topoisomerase-1 1
- Anti-centromere antibodies 1
- Anti-RNA polymerase III 1
- Anti-U1RNP 1
- Anti-Th/To 1
- Anti-PMScl 1
- U3 RNP (fibrillarin) 1
- Anti-Ku 1
Sjögren Syndrome-Specific Testing
If Sjögren syndrome is suspected 1:
Vasculitis-Specific Testing
If vasculitis is suspected 1:
- Anti-neutrophil cytoplasmic antibodies (ANCA) 1
Clinical Rationale and Guideline Recommendations
The American Thoracic Society, European Respiratory Society, Japanese Respiratory Society, and Latin American Thoracic Association jointly recommend performing serological testing as a "motherhood statement" (meaning it is considered essential standard of care) in all patients with newly detected ILD to exclude connective tissue diseases as potential causes. 1
This recommendation exists because 1, 2:
- Nearly 20% of ILDs in Europe and the USA are associated with autoimmune rheumatic diseases 1, 2
- In many CTD-ILDs, lung disease may be the first, dominant, or only feature of the connective tissue disease 1
- Patients may not fit standard rheumatologic diagnostic criteria at initial presentation 1
- Diagnosis of idiopathic pulmonary fibrosis mandates exclusion of other causes of ILD, including CTD-ILD 1
Important Clinical Caveats
A small minority of panelists include all detailed tests listed above as an "ILD panel" at initial screening/baseline evaluation, while most perform the core tests universally and add detailed tests on a case-by-case basis according to associated symptoms and signs. 1
The guideline panel does not refer all patients with new ILD to a rheumatologist; rather, they refer only those with positive clinical manifestations, serologies, or other characteristics atypical for idiopathic pulmonary fibrosis (e.g., female sex, age <60 years). 1
Positive ANA significantly increases the likelihood of CTD diagnosis, with an odds ratio of 14.4 when the titer is >1:320. 2