Setting sample size to ensure narrow confidence intervals for precise estimation of population values.

BACKGROUND: Sample sizes set on the basis of desired power and expected effect size are often too small to yield a confidence interval narrow enough to provide a precise estimate of a population value. APPROACH: Formulae are presented to achieve a confidence interval of desired width for four common statistical tests: finding the population value of a correlation coefficient (Pearson r), the mean difference between two populations (independent- and dependent-samples t tests), and the difference between proportions for two populations (chi-square for contingency tables). DISCUSSION: Use of the formulae is discussed in the context of the two goals of research: (a) determining whether an effect exists and (b) determining how large the effect is. In addition, calculating the sample size needed to find a confidence interval that captures the smallest benefit of clinical importance is addressed.

Measuring women's satisfaction with treatment for sexual dysfunction: development and initial validation of the Women's Inventory of Treatment Satisfaction (WITS-9).

AIM: To develop a brief, psychometrically sound, measure of satisfaction with treatment for female sexual arousal disorder. METHOD: In Phase 1, women in focus groups generated items measuring satisfaction with treatment for arousal disorder. In Phase 2, expert clinicians/researchers and women with self-reported female sexual arousal disorder (FSAD) assessed the content validity of the items. In Phase 3, women enrolled in a double-blind treatment trial for female sexual dysfunction completed the Women's Inventory of Treatment Satisfaction (WITS) and the Female Sexual Function Inventory (FSFI) to provide reliability and validity information. MAIN OUTCOME MEASURES: WITS and FSFI. RESULTS: In Phase 2, 36 items demonstrated adequate content validity. In Phase 3, 20 items correlated with symptom improvement on the FSFI arousal subscale. Factor analysis sorted these items into three dimensions: initiation/receptivity satisfaction, treatment satisfaction, and perceived partner satisfaction. The three items with the highest loadings on each factor formed the WITS-9. Internal consistency (α) reliability coefficients for the total WITS-9 score and the three subscale scores were 0.92, 0.93, 0.92, and 0.79, respectively. Correlations of WITS-9 scores with the FSFI change scores for subgroups with different sexual dysfunctions offer construct validity support that the WITS-9 measures treatment satisfaction for women with a variety of sexual dysfunctions. CONCLUSION: The WITS-9 is a brief, psychometrically sound scale that is useful for assessing treatment satisfaction in women with sexual dysfunctions. While the WITS-9 is promising, further work needs to be done to obtain reliability and validity information in additional samples.

Perceived ejaculatory latency and pleasure in different outlets.

INTRODUCTION: Ejaculatory latencies have been studied in coitus and with masturbation, but not with oral or manual stimulation by a partner. AIM: The present study extended research on ejaculatory latency to these outlets, and investigated the effect of perceived pleasure on self-reported ejaculatory latency. METHOD: A convenience sample of male college students, not selected for sexual dysfunction, completed questionnaires assessing the outcome measures. MAIN OUTCOME MEASURES: Self-report measures of latency to ejaculation in, and perceived pleasure associated with, four different outlets (vaginal intercourse, oral intercourse, manual stimulation by a partner, and masturbation). RESULTS: Ejaculatory latencies in partnered activities were predictive of each other. Masturbatory latencies were predictive of coital latencies but not oral or manual stimulation latencies; all the partnered activities were predictive of each other. There was no difference in time to ejaculation among any of the partnered outlets, although ejaculation occurred more quickly with masturbation than with coitus or manual stimulation. In terms of pleasure associated with the outlets, vaginal and oral intercourse were perceived as equally pleasurable, and both were rated as more pleasurable than manual stimulation or masturbation, which did not differ from each other. CONCLUSIONS: These results suggest that rapidity of ejaculation is consistent across outlets for the partnered sexual activities, and that there is little unique-in terms of ejaculatory latency--about vaginal intercourse compared with oral or manual stimulation by a partner. Masturbation, however, does differ from the partnered activities. Although the average correlation, for individuals, between latency and pleasure for the different outlets is near zero, there are subgroups of men who have (i) a negative relation, (ii) a positive relation, or (iii) no relation. Results show that men, for whom greater pleasure is associated with shorter latency, are more likely to be dissatisfied with their intravaginal ejaculatory latencies, regardless of actual latency.

Canadian and American sex therapists' perceptions of normal and abnormal ejaculatory latencies: how long should intercourse last?

INTRODUCTION: Lay public perceptions about how long intercourse should last are discrepant from objective data on ejaculatory latencies. This may be problematic as the subjective interpretation of latency is a factor related to perceived distress with length of intercourse. AIM: Quantify the opinion of expert sex therapists as to what are "adequate,""desirable,""too short," and "too long" intravaginal ejaculatory latencies. Method. A random sample of members of the Society for Sex Therapy and Research in the United States and Canada was surveyed. MAIN OUTCOME MEASURE: Intravaginal ejaculatory latency, in minutes, for four different conditions: coitus that lasts an amount of time that is "adequate,""desirable,""too short," and "too long." Results. The interquartile range for the sex therapists' opinions regarding an "adequate" length for ejaculatory latency was from 3 to 7 minutes; "desirable" from 7 to 13 minutes; "too short" from 1 to 2 minutes; "too long" from 10 to 30 minutes. CONCLUSIONS: Therapists' beliefs about ejaculatory latencies were consistent with objective data on ejaculatory latency and were not affected by therapist demographic characteristics such as sex or experience. These results suggest that the average sex therapist believes that intercourse that lasts 3 to 13 minutes is normative and not prima facie worthy of clinical concern. Dissemination to the public of these results may change lay expectations for intravaginal ejaculatory latency and prevent distress. These results may also be beneficial to couples in treatment for sexual problems by normalizing expectations.

Prostate-specific antigen changes in hypogonadal men treated with testosterone replacement.

Testosterone supplementation is commonly used as a treatment for hypogonadal men with or without erectile dysfunction. The effect of parenteral testosterone replacement therapy on the development or growth of prostate cancer is unclear. We assessed the effect of this treatment on serum prostate-specific antigen (PSA) levels and risk of prostate cancer in hypogonadal men with erectile dysfunction. Criteria for inclusion were a normal pre-treatment PSA (<4.0 ng/mL) in conjunction with a normal digital rectal examination (DRE) or a negative pretreatment prostate biopsy for men with either an abnormal DRE or an elevated PSA. Patients received intramuscular injections every 2 to 4 weeks, allowing for dose titration. In this retrospective analysis, 54 hypogonadal men with erectile dysfunction were included, with a mean age of 60.4 years (range 42.0-76.0) and a mean follow-up of 30.2 months (range 2.0-82.0) on testosterone therapy. Mean pretreatment total testosterone level was 1.89 ng/mL (range 0.2-2.92), which increased during treatment to a mean of 9.74 ng/mL (range 1.50-26.30, P <.001). Mean pretreatment PSA was 1.86 ng/mL (median 1.01 ng/mL, range 0.0-15.80), which increased to a mean PSA level of 2.82 ng/mL (median 1.56 ng/mL, range 0.0-32.36, P <.01) with testosterone treatment. Of the 54 men included in this study, 6 (11.1%) required prostate biopsy while on testosterone therapy because of a rise in serum PSA above 4.0 ng/mL. One patient (1.9%) was diagnosed with prostate cancer. In conclusion, testosterone replacement therapy in men with erectile dysfunction and hypogonadism is associated with a minor PSA elevation, but there does not appear to be a short-term increase in risk for the development of prostate cancer.

Distribution of chronic prostatitis in radical prostatectomy specimens with up-regulation of bcl-2 in areas of inflammation.

PURPOSE: We examined the anatomical relationship of chronic prostatitis with prostate cancer and benign prostatic hyperplasia (BPH) based on the hypothesis that there may be an association of prostatitis with these other entities that may involve up-regulation of bcl-2. MATERIALS AND METHODS: We examined 40 whole mount radical prostatectomy specimens for the presence and distribution of chronic inflammatory infiltrate. Immunostaining for bcl-2 was done in 10 cases. RESULTS: Chronic prostatitis was identified in all 40 cases with peripheral zone inflammation in 95% and transition zone inflammation in 87.5%. In all cases of transition zone inflammation the infiltrate was noted within and/or around BPH. Inflammatory infiltrate was microscopically associated with prostate cancer in 23 of the 40 cases (57.5%). In these 23 cases, there was no association of inflammation with Gleason score, preoperative prostate specific antigen, positive margins, or seminal vesicle invasion. Patients with BPH unassociated with prostatitis had significantly smaller prostate weight (median 32 gm.) and were younger (mean age 54.4 years) than those with BPH associated with prostatitis (median weight 40 gm. and mean age 61.4 years, p <0.05). Bcl-2 staining was intensified in benign glands within areas of prostatitis in all 10 cases examined. CONCLUSIONS: Chronic prostatitis is a common finding in radical prostatectomy specimens. Inflammation was associated with BPH and cancer but had a greater tendency to be associated with BPH. Bcl-2 was prominently expressed in areas of prostatitis. Our findings indirectly support a potential role for prostatitis in the pathogenesis of BPH.