'Potency': the validation of information from a self-administered questionnaire using objective measurements of night-time erections and test-retest reliability.

OBJECTIVE

To assess the validity and reliability of a questionnaire assessing 'physiological potency'.

PATIENTS AND METHODS

The study comprised 89 patients with prostate cancer and 43 men without; the latter were attending a consultation clinic because of problems with erection. All men answered three questions assessing erectile rigidity during sexual activity, morning and spontaneous erections. In the questionnaire, 'potency' was defined as erectile rigidity 'sufficient for intercourse most of the time' or better. 'Potency' in one or more of the three aspects of erection was defined as 'physiological potency'. The patients with prostate cancer answered the questionnaire twice with a 3-week interval. The men attending the consultation clinic underwent two nights of erectile monitoring (using the RigiScan device) and the minimum criterion for RigiScan potency was defined as 55% rigidity at both tip and base.

RESULTS

The test-retest assessment showed 93% conformity in the questionnaire diagnosis of 'physiological potency/impotence' between the tests. The sensitivity and specificity of the questionnaire assessment compared with the RigiScan method were 40% and 100%, respectively, when the question assessing sexually stimulated erectile rigidity was used alone. Using 'physiological potency', the sensitivity increased to about 60% without jeopardizing the specificity, and when men reporting depression were excluded from the analysis, the sensitivity increased to about 80%.

CONCLUSIONS

The test-retest reliability of the questionnaire was satisfactory. Using questions in a self-administered questionnaire, 'physiological impotence' can be diagnosed with complete and 'physiological potency' with 60-80% sensitivity. The sensitivity of the self-assessment for 'potency' depended on the number of questions asked and the proportion of men reporting depression.