Cholesterol in Pleural Effusions: A Diagnostic Aid

doi:10.1378/chest.92.2.296

Chest

Volume 92, Issue 2, August 1987, Pages 296-302

https://doi.org/10.1378/chest.92.2.296 Get rights and content

In this prospective study of 70 patients with pleural effusion, the underlying disease could be identified in 62 cases. By predefined criteria, 31 of these effusions were classified as transudates and 31 as exudates. Pleural fluid protein content, LDH activity and cholesterol level were measured to investigate their utility in differentiating the exudates from the transudates. Protein and LDH levels, and their pleural fluid-to-serum ratios, resulted in erroneous classification of 11 to 15 percent of the effusions. Mean cholesterol level in malignant effusions was 94 mg/dl, 76 mg/dl in inflammatory effusions and 30 mg/dl in the transudates. Using a dividing line of 60 mg/dl to separate the exudates from the transudates, only 5 percent were incorrectly classified. Elevated cholesterol levels in exudates seem to be independent of the serum levels. Our findings indicate that the pleural fluid cholesterol level is a simple and cost-effective aid in differentiating exudative from transudative pleural effusions.

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PATIENTS AND METHODS

Seventy pleural effusions from 70 consecutive patients admitted to our hospital were studied prospectively between August, 1984 and May, 1985.

Diagnosis of pleural effusion was established by physical examination, chest x-ray film and in several cases by ultrasound study. In small effusions, an ultrasound-guided thoracocentesis was performed.

The patients were placed in four different diagnostic groups: 1) transudates in congestive heart failure/other transudates (CHF/OTH TRANS); 2) exudates of

GROUP 1

Congestive heart failure was determined by an enlarged heart, x-ray signs of congested lungs, peripheral edema, response to treatment of CHF, and/or absence of malignancy or pulmonary infiltrates.

Liver cirrhosis was diagnosed by clear evidence of liver cirrhosis in the absence of heart failure, malignancy or pulmonary infiltrates, and responsiveness to diuretic treatment.

Nephrosis, hypalbuminemia and other causes of transudates were not observed.

GROUP 2

Exudates of a malignant origin fit the following criteria: histologic proof of a malignant tumor; cytologic and/or histologic evidence of a malignant pleural effusion; absence of diseases causing transudates; and no pulmonary infiltrates.

GROUP 3

Pleuropneumonia appeared with fever, pulmonary infiltrates, responsiveness to antibiotic treatment, and the absence of malignancy or diseases causing transudates.

Tuberculosis was diagnosed by granulomas on pleural biopsy and/ or positive pleural fluid cultures.

GROUP 4

Patients with effusions meeting diagnostic criteria of more than one of the previous groups (eg, CHF and pleuropneumonia) or with pleural effusions of obscure origin fell into the fourth diagnostic group.

No chylous or traumatic effusions were observed.

Samples of venous blood and pleural fluid were usually obtained on the same day shortly after hospital admission. Only the results of the first thoracocentesis were considered.

Protein level was measured by the biuret method (Boehringer-Mannheim).

RESULTS

Classification of the 70 effusions is shown in Table 1. Group 4 includes patients with CHF and carcinoma (two cases), CHF and pleuropneumonia (two cases), probable carcinoma and pleuropneumonia (one case), non-Hodgkin lymphoma and CHF (one case), uremia and CHF (one case), and probable pulmonary infarction (one case).

Table 2 summarizes cytopathologic and histologic findings in the group with exudates of malignant origin. Case 10 was a patient with advanced metastatic lung cancer with extensive

DISCUSSION

Early and decisive evidence of the transudative or exudative nature of a pleural effusion may be of considerable clinical value and is often used as a basis for further diagnostic procedures and therapeutic considerations. No single chemical test or series of tests has yet proved to be completely reliable. Hence, the search for diagnostic improvements is kept alive.

It has long been known that cholesterol is constantly found in all pleural fluids.⁸ Nevertheless, we were not able to find

ACKNOWLEDGMENT

We thank Professor Berger (Institute of Biostatistics, University of Hamburg) for statistical guidance; Professor Saeger (Department of Pathology, Marienkrankenhaus, Hamburg) for cytopathologic and histologic studies; and Professor Ostendorf (Director, First Medical Department, Marienkrankenhaus, Hamburg) for continuous and critical revision of the manuscript. The authors are indebted to Ms. M. Petersen for her technical assistance and for preparation of the manuscript.

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: Manuscript received September 15; revision accepted January 13.

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