Principles of bladder cancer screening in an intervention trial.

Screening for preclinical disease in asymptomatic people is an accepted activity in occupational health programs, public health programs, and physicians' offices. Yet, only diseases with high morbidity and mortality, a detectable, prolonged preclinical phase, and treatment that can improve survival if applied before the onset of clinical manifestations are suitable for screening. Furthermore, the screening test must be simple to perform, acceptable to providers and recipients, safe, reasonably pain-free, low-cost, and a valid estimator of the true disease state. Even so, screening will succeed only if the condition has a high prevalence in the population being screened, in order that enough persons with disease are identified and treated to justify the cost and the stress experienced by screen-positive, disease-negative subjects. The ultimate goal of screening is to reduce disease-specific mortality. The one recognized study design that can demonstrate a reduction in mortality from cancer of the urinary bladder is a randomized, controlled clinical trial of a screening modality, eg, urinary cytology, in a population previously exposed to occupational carcinogens.