Antinuclear antibodies in pleural fluid

Area of Science:

• Immunology
• Pulmonology
• Rheumatology

Background:

• Systemic lupus erythematosus (SLE) commonly affects the pleura, causing pleural effusion.
• Previous studies showed animal-tissue-based antinuclear antibody (ANA) tests in pleural fluid were effective for SLE diagnosis.
• The HEp-2 ANA assay, using a human cell line, is now preferred but unstudied in pleural fluid.

Purpose of the Study:

• To evaluate the sensitivity and specificity of the HEp-2 ANA assay in pleural fluid for diagnosing SLE-related pleural effusions.
• To compare HEp-2 ANA results in pleural effusions from SLE patients versus those with other conditions.

Main Methods:

• HEp-2 ANA levels were measured in pleural effusion samples from patients with various conditions, including SLE, malignancy, heart failure, pneumonia, and tuberculosis.
• Pleural fluid samples were analyzed for ANA positivity, titer, and staining pattern.

Main Results:

• Pleural fluid ANA was positive in 14 of 82 samples (17.1%).
• Six of eight SLE patients (75%) had positive pleural fluid ANA, mostly with high titers and a homogenous pattern.
• Eight of 74 non-SLE patients (10.8%) had positive pleural fluid ANA, typically with a speckled pattern and lower titers.

Conclusions:

• A negative or low titer HEp-2 ANA with a speckled pattern in pleural fluid suggests an alternative diagnosis to lupus pleuritis.
• High titer HEp-2 ANA in pleural fluid can occasionally be seen in non-SLE inflammatory effusions.