Evaluation of the pleural fluid Rivalta test for diagnosing pleural effusion

The Rivalta test is commonly used to differentiate exudates from transudates in body cavity effusions. However, its diagnostic utility for pleural effusion remains uncertain. This study aimed to evaluate the diagnostic performance of the Rivalta test in differentiating various types of pleural effusions.

Data were retrospectively collected from 1158 patients at Fukujuji Hospital between January 2012 and June 2024. The cohort included 202 patients with tuberculous pleurisy, 246 with pleural infection, 427 with malignant pleural effusion, 76 with transudative pleural effusion, and 207 with other diseases. Rivalta test-positive and Rivalta test-negative groups were compared, along with the Rivalta test results across five disease groups.

Among all patients, 1099 (94.9 %) had a positive Rivalta test, while 59 (5.1 %) had a negative Rivalta test. Serum C-reactive protein and total pleural protein levels were significantly lower in the Rivalta test-negative group. A negative Rivalta test was significantly associated with transudative pleural effusion compared with exudative pleural effusion (tuberculous pleurisy, pleural infection, malignant pleural effusion, and other diseases) (p < 0.001), whereas no significant differences were observed among the exudative groups. The negative Rivalta test showed 35.5 % sensitivity and 97.0 % specificity for identifying transudative pleural effusion. The Rivalta test showed lower diagnostic accuracy than Light's criteria did (McNemar test, p < 0.001). When added to Light's criteria, the diagnostic accuracy decreased, with a net reclassification improvement of -65 %.

This study demonstrates that the Rivalta test has lower diagnostic utility than Light's criteria and should not be incorporated into pleural effusion examinations.