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Monte Carlo simulations are commonplace in quantitative risk assessments (QRAs). Designed to propagate the variability and uncertainty associated with each individual exposure input parameter in a quantitative risk assessment, Monte Carlo methods statistically combine the individual parameter distributions to yield a single, overall distribution. Critical to such an assessment is the representativeness of each individual input distribution. The authors performed a literature review to collect and compare the distributions used in published QRAs for the parameters of body weight, food consumption, soil ingestion rates, breathing rates, and fluid intake. To provide a basis for comparison, all estimated exposure parameter distributions were evaluated with respect to four properties: consistency, accuracy, precision, and specificity. The results varied depending on the exposure parameter. Even where extensive, well-collected data exist, investigators used a variety of different distributional shapes to approximate these data. Where such data do not exist, investigators have collected their own data, often leading to substantial disparity in parameter estimates and subsequent choice of distribution. The present findings indicate that more attention must be paid to the data underlying these distributional choices. More emphasis should be placed on sensitivity analyses, quantifying the impact of assumptions, and on discussion of sources of variation as part of the presentation of any risk assessment results. If such practices and disclosures are followed, it is believed that Monte Carlo simulations can greatly enhance the accuracy and appropriateness of specific risk assessments. Without such disclosures, researchers will be increasing the size of the risk assessment "black box," a concern already raised by many critics of more traditional risk assessments.

The effects of urinary symptoms on health-related quality of life (HRQL) are important in therapeutic decision making. Few have evaluated the treatment effects on HRQL in men with benign prostatic hyperplasia (BPH), even though increased urinary symptoms are associated with greater worry, bother, and interference with living activities. We report on patient assessments of such disease-specific measures as well as general HRQL measures from two placebo-controlled clinical trials of finasteride in the treatment of symptomatic BPH. Patients treated with finasteride appeared to have greater improvement than placebo-treated patients in disease-specific measures and in patient global assessment. The treated group appeared to have a greater mean increase in sexual domain scores. As expected, general measures (health rating, life satisfaction, ladder of life) changed little. Thus, treatment with finasteride appears to reduce bother, worry, and activity interference due to symptoms but in a small percentage of men may lead to slightly reduced sexual function.