Semi-quantitative analysis of telomerase activity of exfoliated cells in urine of patients with urothelial cancers: Causative factors affecting sensitivity and specificity

We previously reported that detection of telomerase activity in urinary exfoliated cells obtained from urothelial cancer patients by telomeric repeat amplification protocol (TRAP) assay is a more sensitive method of diagnosis than conventional urine cytologic examination, particularly in patients with grade 1 tumors. To establish this method as a noninvasive screening test for the diagnosis of urothelial cancers, we performed the semi-quantitative analysis of telomerase activity using Telomerase PCR ELISA™. Spontaneous voided urine samples were obtained from 65 urothelial and 58 non-urothelial cancer patients. When the mean + 2 standard deviation of telomerase activity in urine sediments of non-urothelial cancer patients was arbitrarily determined as a cut-off, the sensitivity of TRAP enzyme-linked immunosorbent assay (ELISA) and the conventional cytology were 57% and 35%, respectively. Detection rate was significantly higher in semi-quantitative TRAP assay than in conventional cytologic examination in grade 1 cancer patients (52% vs. 5%, p = 0.00195). False positives were detected in 5% of non-urothelial cancer patients without pyuria and in 11% of non-urothelial cancer patients with pyuria (p = 0.395). Telomerase activity was enhanced in some cases after phenol extraction or extracting epithelial cells by using Dynabeads of macroscopic hematuria and pyuria, indicating that hematuria and pyuria might contribute to false negatives. In conclusion, the TRAP-ELISA method is superior to the standard TRAP assay in quantitativeness and simplicity of the experimental procedure. Detection of telomerase activity in urine sediments is particularly useful for the diagnosis of low-grade tumors. However, telomerase activity in patients with high grade tumors often might be underestimated due to the excessive amount of exfoliated epithelia with necrotic tissues, hematuria, and pyuria.