Limitations of detection of malignancy in pleural effusions using ELISA-based TRAP assay: comparison with cytological examination.

OBJECTIVE

Telomerase is active in almost all cancers from various organs but is not detectable in most normal cells. Thus, telomerase activity might be a universal and specific marker for diagnosing malignancy. The aim was to evaluate the potential use of the ELISA-based TRAP assay to detect malignancy in pleural effusion, and to compare it with conventional cytological examination.

METHODS

Using the ELISA-based TRAP assay, telomerase activity was examined in 94 consecutive pleural effusions submitted for cytological examination.

RESULTS

According to the results of cytology, the 94 samples were divided into two groups: group I, 79 non-malignant pleural effusions, including group IA, no association with a malignant tumour, a control group (n = 63), and group IB, associated with a malignant tumour (n = 16); and group II, 15 malignant pleural effusions. Telomerase activity was detected in five of 63 samples in group IA (7.9%), four of 16 samples in group IB (25%), and six of 15 samples in group II (40%). All five false-positive effusions were from patients with tuberculosis. Comparing group II with group IA, the TRAP assay showed 40% sensitivity, 92.1% specificity, 54.5% positive and 86.6% negative predictive value, and 82.1% accuracy. However, the detection rate of the TRAP assay (88.9%) was higher than that of the cytological examination (66.7%) in lung cancer-inflicted pleural effusions.

CONCLUSION

The ELISA-based TRAP assay is relatively insensitive; therefore, it is unsuitable as a routine diagnostic tool for pleural effusion. False-positive telomerase activity due to lymphocytic contamination may weaken its diagnostic value for malignant effusions in a tuberculosis-endemic area.