The implication of elevated carcinoembryonic antigen level in pleural fluid of patients with non-malignant pleural effusion.

OBJECTIVE

The aim of this study was to evaluate the false positive rate for pleural fluid carcinoembryonic antigen (CEA) level in non-malignant pleural effusions and to determine whether the falsely elevated CEA level has any relation to other biochemical parameters of pleural effusions.

METHODOLOGY

We performed a retrospective analysis of 654 consecutive patients with a pleural effusion admitted to the pulmonary department of a tertiary referral teaching hospital from March 1997 to March 1999. The aetiology of the pleural effusions were classified as tuberculosis (n = 262), malignancy (n = 204), pneumonia (n = 145), exudates of other origin (n = 28) and transudate (n = 1).

RESULTS

A false positive result for pleural fluid CEA level (> 5 ng/mL) was registered in 13.8% of non-malignant pleural effusion cases: empyema (38.6%), parapneumonic effusion (14.7%), exudates of other origin (14.3%), tuberculosis (7.3%) and transudate (6.7%). In analysis of the subgroup with false positive results for pleural fluid CEA level, the CEA level of non-malignant pleural effusion showed a significant relationship to the severity of pleural inflammation in terms of the following variables: LDH (rs = 0.4201, P= 0.001), adenosine deaminase (ADA) (rs = 0.4440, P= 0.0004), white blood cell count (rs = 0.4266, P= 0.0004), polymorphonuclear cell percentage (rs = 0.5080, P= 0.0001), and polymorphonuclear cell count (rs = 0.5095, P= 0.0002). In the parapneumonic effusion and empyema groups, the changes in pleural fluid CEA level exhibited a positive association with the changes in the pleural fluid ADA level (rs = 0.8143, P= 0.0002).

CONCLUSIONS

The results from our series indicated that false positive results for pleural fluid CEA level were most commonly observed in patients with empyema and parapneumonic effusion and the CEA level showed a significant correlation to the indices of pleural inflammation. The serial measurement of pleural fluid CEA level may be useful as a means of monitoring resolution of pleural inflammation and excluding the possibility of a malignant pleural effusion.