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Protein Zone Electrophoresis of Pleural Effusion: The Diagnostic Separation of Transudates and Exudates

¹ Department of Pathology, Princess Margaret Hospital, Hong Kong, China

² Department of Chemical Pathology, The Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong, China
^a Author for correspondence. Fax 852-2636-5090; e-mail ching-wanlam@cuhk.edu.hk.

To the Editor:

The cause of a pleural effusion is not always easily determined. Invasive procedures such as pleural biopsy are indicated only in patients with exudative pleural effusions. Therefore, a frequent early step in the evaluation of pleural effusions is to classify them as transudates or exudates.

The diagnostic criteria developed by Light et al. (1) characterize pleural exudates as having at least one of the following: pleural fluid/serum total protein ratio >0.5; pleural fluid/serum lactate dehydrogenase (LDH) ratio >0.6, and pleural fluid LDH more than two-thirds of the upper reference limit of serum LDH. However, the results produced by Light et al. (1) are not always reproducible (2), and the low specificity of the criteria of Light et al. may lead to unwarranted invasive intervention in up to 20–30% of patients with transudates (3).

One report (4) described the use of protein electrophoresis (by Tiselius U-tube) to study patterns of protein in pleural fluid in disease but did not address the role of protein zone electrophoresis (PZE) in the differentiation of exudate from transudate. We postulate that low-molecular weight molecules such as albumin (M_r 66 400), ₁-antitrypsin (M_r 54 000), and transferrin (M_r 76 500) pass through the pleura to enter the pleural spaces in transudative pleural effusion, whereas high-molecular weight molecules such as ₂-macroglobulin (M_r 725 000), haptoglobin (M_r 400 000), immunoglobulin (IgG, M_r 150 000; IgA, M_r 160 000; IgM, M_r 950 000), and ß-lipoprotein (M_r 250 000) do so only when capillary permeability increases in exudative pleural effusion formation.

We tested our hypothesis in patients who presented with pleural effusion in the Princess Margaret Hospital during 1997–1998. No selection criteria were set with . . . [Full Text of this Article]

Acknowledgments

References

The following articles in journals at HighWire Press have cited this article:

				R. Claeys, C. Groven, and F. K. Gorus Capillary Zone Electrophoresis of Proteins in Body Fluids: Comparison of Capillary and Agarose Gel Electrophoresis Clin. Chem., May 1, 2001; 47(5): 967 - 970. [Full Text] [PDF]

				J. M. Porcel, M. Vives, A. Esquerda, M. C. Rivas, C.-W. Lam, and M.-L. Chen Pleural Protein Capillary Electrophoresis for the Separation of Transudates and Exudates Drs. Lam and Chen respond: Clin. Chem., May 1, 2001; 47(5): 975 - 976. [Full Text] [PDF]