Comparison of different diagnostic methods for lupus pleuritis and pericarditis: A prospective three-year study

Background and purpose: Pleural or pericardial effusions, or both, are commonly encountered, but the differential diagnosis is sometimes difficult. We evaluated the diagnostic value of effusion immunofluorescent antinuclear antibody (ANA) titer, systemic lupus erythematosus (SLE) latex agglutination slide test, and cytologic LE cell examination in patients with pleural and/or pericardial effusions of various etiologies. Methods: A total of 153 pleural and/or pericardial effusion specimens were collected by aspiration from 152 patients (14 SLE and 138 non-SLE patients). All specimens were sent for routine biochemistry testing, determination of ANA titer, SLE latex agglutination slide test, and LE cell examination. Results: Ten of the 14 SLE patients had lupus serositis and all of them had high ANA titers (≥ 1:160) in their effusions. SLE latex and LE cell tests were positive in seven and eight patients with lupus serositis, respectively. The remaining four SLE patients with effusion of etiologies other than lupus serositis had low or negative effusion ANA titers. Among the non-SLE patients, 29 of 112 patients (26%) with pleural effusion and six of 26 patients (23%) with pericardial effusion had positive ANA tests (≥ 1:40). None of them had a positive SLE latex or LE cell test result. Thirteen of the 138 non-SLE patients (11%) had high effusion ANA titers (≥ 1:160). Effusion in 11 of 13 non-SLE patients (85%) was due to malignancy. Conclusions: Effusion ANA titer detection is a very sensitive but nonspecific test for the diagnosis of lupus serositis. SLE latex and cytologic LE cell tests can aid in the differential diagnosis as complementary tools. The specificity, positive and negative predictive values of these two tests are excellent for the diagnosis of lupus serositis.