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Accurate laboratory detection of bladder cancer requires close followup with repeated testing
Urine cytology is generally accurate for screening and diagnosing bladder cancer. For example, a study of patients at one hospital showed that not a single patient in a 2-year period suffered severe harm on the basis of a test failure to diagnose bladder cancer. However, nearly half (48.6 percent) of patients with discrepancies in their cytologic (cell) and followup histologic (tissue) samples had a delayed diagnosis of one month or longer and/or repeated, unnecessary testing. This suggests that maintaining a high level of vigilance in bladder cancer detection is costly and requires close followup with repeated testing, concludes Stephen S. Raab, M.D., of the University of Pittsburgh School of Medicine.
The study found that in 41 percent of cases, analysis of bladder cells via urine, lower urinary tract specimens, or upper urinary tract specimens differed from followup tissue analysis. Sample interpretation problems and inadequate samples were the cause of 35 percent and 63 percent of discrepancies, respectively.
False-negative results can be due to the inability to sample some lesions (for example, voided urine specimens may not contain shed cancer cells or may contain obscuring debris such as blood or inflammation) or to difficulties in diagnosing some entities (for example, low-grade cancers cytologically resemble non-cancerous urinary tract lining).
False-positive test results are often due to mimics of cancerous bladder cells (for example, polyoma virus). Study findings were based on histologic followup in 6.2 percent of 361 voided urine, 19.5 percent of 636 lower tract instrumented, and 33 percent of 69 upper tract urinary cytologic specimens from one institution laboratory during a 2-year period. Cytologic diagnoses were initially classified as unsatisfactory, benign, atypical, suspicious, or malignant.
The study was supported by the Agency for healthcare Research and Quality (HS13321).
More details are in "Urine cytology discrepancies: Frequency, causes, and outcomes," by Dr. Raab, Dana Marie Grzybicki, M.D., Ph.D., Colleen M. Vrbin, and Kim R. Geisinger, M.D., in the American Journal of Clinical Pathology 127(6), pp. 946-953, 2007.
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