Aim: To evaluate the diagnostic contribution and clinical relevance of analysing subpopulations of lymphocytes in pleural effusions.
Methods: Forty patients (age >60 years) with newly diagnosed, polyclonal, lymphocyte-rich pleural effusions were evaluated. The following data were collected: demographic characteristics, associated diseases, fluid type, fluid white blood cells count, differential morphology and immunephenotyping, and final diagnosis.
Results: Of the 33 patients for whom biochemical data were available, 18 had exudative effusion, while 15 had transudate. Thirty-three fluids contained mostly T cells and only one was B-cell rich. (The lymphocytes of five patients with malignant epithelial cells in the effusion were not subtyped.) Thirty-two of the 33 T-cell rich fluids contained mainly CD4+ lymphocytes. The most common causes of pleural effusion were congestive heart failure (17 patients) and epithelial malignant diseases (eight patients), while none of the patients had tuberculosis. Since most effusions were CD4+ rich, no correlation could be detected between lymphocyte subtyping and diagnosis or the biochemical type of the fluids. Congestive heart failure was significantly associated with transudates, while malignant diseases correlated with exudates.
Conclusions: Most patients with pleural polyclonal lymphocytosis, especially those with transudates, have congestive heart failure. The presence of exudative, lymphocyte-rich effusion is an indication for further evaluation, since it is most commonly associated with malignancy. The clinical value of lymphocyte subtyping is low and this procedure should not be used routinely.