ANTINUCLEAR ANTIBODIES IN PLEURAL FLUID

Systemic lupus erythematosus (SLE) frequently involves the pleura with resultant pleural effusion. Previous studies have reported that detec tion of antinuclear antibodies (ANA) in pleural fluid using animal tis sue as substrate was a sensitive and specific method for distinguishin g SLE pleural effusions from other etiologies. The HEp-2 ANA, which us es a human cell line as substrate, is now the preferred ANA test; howe ver, to our knowledge, no studies on pleural fluid using this assay ha ve been reported. To determine its sensitivity and specificity, when m easured in pleural fluid, HEp-2 ANA levels were determined in pleural effusion samples associated with a variety of different etiologies, in cluding SLE, malignancy, congestive heart failure, pneumonia, tubercul osis, and a miscellaneous group of diseases. Pleural fluid ANA results were positive in 14 of 82 samples. Six of the eight (75 percent) pleu ral fluid samples collected from patients with SLE were ANA positive, and all but one had high titers (>1:160) with a homogenous staining pa ttern. The remaining two patients with SLE with negative pleural fluid ANA had recurrent pulmonary;emboli and congestive heart failure, rath er than lupus pleuritis. Eight of 74 patients (10.8 percent) without c linical evidence of SLE had a positive pleural fluid ANA, with the maj ority having a speckled pattern. High titers were noted in three. Thes e results indicate that a negative or low titer ANA and a speckled sta ining pattern in pleural fluid from a patient suspected of lupus pleur itis suggest an alternative diagnosis. High pleural fluid titers (up t o 1:640) were seen occasionally in patients with inflammatory pleural effusions in the absence of SLE.