The quality of erection questionnaire is a new six-item patient-reported outcome for evaluating the quality of erections in terms of hardness, onset, and duration, as well as for assessing changes in erection quality with successful treatment of erectile dysfunction.
Although the past decade has seen the development of many patient-reported outcome's to evaluate erectile dysfunction, the quality of erection questionnaire is unique in that it is the only psychometrically validated assessment tool designed to solely and specifically evaluate satisfaction with the quality of erections.
The development and validation of the erection questionnaire were described previously.
In prospective trials of flexible-dose sildenafil citrate (25, 50 or 100 mg) for the treatment of men with erectile dysfunction, the mean±s.d. transformed erection questionnaire total score increased by more than 40 points, from baseline values of 22 and 34 points, in men treated with sildenafil. Furthermore, the erection questionnaire had convergent validity with measures of sexual function (International Index of Erectile Function (IIEF), erection hardness (Erection Hardness Score), satisfaction (Erectile Dysfunction Inventory of Treatment Satisfaction) and emotional well-being.
Health-status measures have become a standard and essential part of validated patient-reported outcome's in many different types of diseases. However, to understand the relevance of outcomes on a health-status measure, it is crucial to be able to interpret the scores and have established criteria for determining the meaningfulness of changes in scores. Such an understanding is important, not only in helping complete a psychometric evaluation, but also in designing trials, evaluating interventions, informing consumers and health policy makers, and providing information for formulary and reimbursement decisions.
The importance of determining the minimum important difference threshold is highlighted by the inclusion of a discussion in the US Food and Drug Administration’s draft guidance for industry, ‘Patient-Reported Outcome Measures: Use in Medical Product Development to Support Labeling Claims’.
For a new patient-reported outcome instrument, clinically meaningful change can be estimated using an anchor-based approach in which change on the new instrument is compared with change in disease status. Assessing change in disease status in some areas such as sexual health must be through self-report by the patient. In this case, a known disease-related measure that has clinical relevance and has an appreciable association with the targeted healthstatus measure can be used.
Another approach relies on the statistical characteristics of a study sample—a distribution-based approach which can be used to attempt to corroborate estimates from an anchor-based approach (and vice versa).
As a clinically meaningful improvement definition is crucial to understanding the relevance of treatment on health-status measures, we estimated the clinically meaningful improvement and the minimal clinically meaningful improvement on the erection questionnaire using an anchor-based approach and a distribution-based approach which can be used to attempt to corroborate estimates from an anchor-based approach (and vice versa).
The clinical trials enrolled 594 men aged 23–65 years (53.8±8.1 years), 558 of whom completed baseline and postbaseline quality of erection questionnaire measurements. Between the two clinical trial populations (n=223 and n=335, respectively), a statistically significant difference was found in the mean duration of erectile dysfunction (5.3 (range, 0.5–31) versus 6.9 (range, 0.7–35) years) at baseline; this was not expected to affect the results. In 542 of the men, erectile dysfunction was categorized according to IIEF Erectile Function domain scores: mild ED (n=44), mild-to-moderate ED (n=119), moderate ED (n=171) and severe ED (n=208). A total of 95 men improved by 1 IIEF Erectile Function domain severity category, and 116 men had no change in IIEF Erectile Function domain severity category.
The mean change from baseline to end of treatment in the quality of erection questionnaire total score for the men who improved by 1 erectile dysfunction severity category (the anchorbased group) was 22.4 (s.d., 2.2)—defined as the clinically meaningful improvemen; the minimal clinically meaningful improvemen, estimated from the lower bound of the 95% CI, was 18.0. Using the difference of this mean score of 22.4 and that from the 116 men who had no change in erectile dysfunction severity (the anchor group minus the no-change group), the clinically meaningful improvemen was 17.7 (s.d., 2.9) and the minimal clinically meaningful improvemen was 12 points.
According to the distribution-based analyses, the baseline 1 s.e.m. was 7.99, the end-of-treatment 1 s.e.m. was 8.22 and the s.e. of the difference was 11.46. Compared with the anchor-based minimal clinically meaningful improvemen estimate of 12 points (based on data from the anchor group minus the no-change group), these s.e.m. values are only slightly lower, and the s.e. of the difference value is approximately equivalent.
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