This lack of evidence of effectiveness does not constitute evidence of ineffectiveness. In other cases, studies may have been performed but they may have produced conflicting results. Studies showing no benefit may lack adequate statistical power, making it unclear whether the maneuver would be proved effective if it were tested with a larger sample size. Practitioners and policy makers often need to consider factors other than science, however, in deciding how to proceed in the absence of evidence. The first of these considerations is potential harm to the patient.
Similar considerations apply to costs.
The burden of suffering from the target condition may justify the performance of preventive services, even in the absence of evidence, and similar considerations may apply to an individual patient's risk status. Unproven preventive services that are inappropriate for the general population may be appropriate to consider for individuals at markedly increased risk of the disease. Patient preferences, which are important in all clinical decisions, are essential to consider when contemplating the performance of preventive services of unproven effectiveness. The clinician's responsibility is to provide the patient with the best available information about the potential benefits and harms of the preventive service and to delineate what is known and not known about the probability of these outcomes. Patients can then make informed decisions about which option is appropriate, based on the relative importance that they assign to these outcomes.