Lab Testing for Bladder Cancer
Essential Laboratory Tests for Initial Diagnosis
The core laboratory workup for suspected bladder cancer includes urine cytology, complete blood count, comprehensive metabolic panel (including liver function tests and alkaline phosphatase), and urinalysis with microscopy 1, 2.
Urine Cytology
Urine cytology is the gold standard non-invasive laboratory test for bladder cancer detection and monitoring, with high specificity (98.3%) but variable sensitivity depending on tumor grade 1, 3.
Sensitivity is excellent for high-grade tumors and carcinoma in situ (84%), but poor for low-grade/G1 tumors (16%) 1, 3.
Urine cytology can detect malignant cells from anywhere in the urinary tract, making it valuable when cystoscopy is negative but suspicion remains high 1, 2.
The test should be obtained around the time of cystoscopy as part of the initial diagnostic workup 2.
Blood Work
Complete blood count and comprehensive metabolic panel (including liver function tests) are mandatory for all patients 1.
Alkaline phosphatase levels must be checked, as elevation warrants bone scan to evaluate for metastatic disease 1.
Liver function tests are particularly important for patients with high risk of metastases 1, 2.
Laboratory Tests for Disease Monitoring
Surveillance Cytology
Urine cytology remains essential for monitoring all patients with urothelial neoplasms during follow-up, and when consistently used can actually decrease the frequency of cystoscopy 4.
In patients with positive cytology but negative cystoscopy and imaging, transurethral resection with directed or mapping biopsies must be performed, including evaluation of the prostatic urethra and upper tract cytology 1.
FDA-Approved Urinary Biomarkers
Consideration may be given to FDA-approved urinary biomarker testing using fluorescence in situ hybridization (FISH) or nuclear matrix protein 22 (NMP22) for monitoring recurrence 1.
The BTA stat Test can provide diagnostic aid in cases of suspicious (class III) cytology, with sensitivity of 66.7% and specificity of 58.3% in this specific context 5.
Important Caveats and Pitfalls
Cytology Limitations
Urine cytology requires expertise for interpretation, particularly for low-grade lesions which lack many features of malignancy 4.
Alkylating agents (Cytoxan, thio-TEPA, mitomycin C) produce characteristic changes in urothelial cells that rarely mimic carcinoma, so prior treatment should not confound diagnosis 4.
Suspicious cytology (class III) indicates a high-risk group, with approximately one-third having recurrence at cystoscopy or subsequent follow-up 5.
Specimen Handling
Freshly voided, randomly collected urine is the most useful specimen type for routine diagnostic interpretation 4.
Refrigeration is required to prevent bacterial growth and cellular degeneration; alcohol preservation is unnecessary unless prolonged storage is contemplated 4.
Catheterized specimens and bladder washings may yield more cells but show no significant difference in sensitivity and specificity compared to voided urine 4, 3.
Critical Point
No urinary biomarker can replace cystoscopy for definitive diagnosis, but they serve as helpful adjuncts for specific diagnostic problems 3, 6.
The final diagnosis of bladder cancer is always based on cystoscopic examination and histological evaluation of tissue obtained via biopsy or transurethral resection 1.