Validation of stopwatch measurements of erection duration against responses to the sexual encounter profile and international index of erectile Function in patients treated with a phosphodiesterase type 5 inhibitor

James W Shaw, Gregory Reardon, David W Sandor, Raymond C Rosen, David M Ferguson
Journal of Sexual Medicine 2010, 7 (3): 1147-59

INTRODUCTION: Although the Sexual Encounter Profile (SEP) and International Index of Erectile Function (IIEF) are frequently used to measure erectile dysfunction (ED) treatment outcomes, stopwatch-assessed duration of erection is a new, objective, and potentially useful endpoint of ED treatment effect.

AIMS: To assess the validity and reliability of stopwatch-assessed erection duration against responses to SEP items 2 (SEP-2) and 3 (SEP-3) and IIEF scale scores.

METHODS: Data were taken from a multi-center trial of vardenafil for the treatment of ED. Patients were randomized to vardenafil 10 mg or placebo for 4 weeks. After a 1-week washout period, patients received the alternate therapy for an additional 4 weeks. An electronic diary was used to record information about sexual attempts. The duration of erection was measured using a stopwatch and transcribed into the diary. The SEP was completed following each sexual attempt, and the IIEF was completed at the end of each treatment period.

MAIN OUTCOME MEASURES: Mean and median values of erection duration, mean SEP-2 and SEP-3 success rates, and scores for each of the 5 IIEF scales were calculated.

RESULTS: At baseline, correlations of median erection duration with the 5 IIEF scale scores ranged from 0.06 to 0.53, while correlations with mean SEP-2 and SEP-3 success rates were 0.66 and 0.49, respectively. Compared with the other measures, mean and median values of erection duration were less sensitive to differences between placebo- and vardenafil-treated patients and less responsive to clinical change associated with treatment crossover. However, mean erection duration exhibited a good level of reliability (intraclass correlation coefficient = 0.72, P < 0.001).

CONCLUSIONS: This study provides evidence for the validity and reliability of stopwatch-assessed duration of erection. Our findings suggest that erection duration is suitable for use as a unique endpoint in ED treatment-efficacy trials conducted for phosphodiesterase type 5 inhibitors.

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