Nocturnal penile erections: A retrospective study of the role of RigiScan in predicting the response to sildenafil in erectile dysfunction patients

Sildenafil enhances the nitric oxide–cGMP pathway of erection, which is claimed to have a role in nocturnal penile tumescence and rigidity (NPTR). This study aimed to find whether RigiScan can predict the response to sildenafil among erectile dysfunction (ED) patients and to find which RigiScan parameter produces the best prediction. Medical records of 172 ED patients were revised regarding their full sexual history, standard andrology examination, NPTR monitoring by the RigiScan device, and the degree of response to sildenafil. Of 172 ED patients, 94 patients (54.7%) were sildenafil responders. All RigiScan parameters were higher in the sildenafil responder group. The RigiScan parameters with the most differentiating power between both sildenafil responders and non-responders were base rigidity (AUC 0.860) and then tip rigidity (AUC 0.831). The cut-off value of base and tip rigidity with the highest diagnostic accuracy was 42.5%. This finding was found to be more specific than the sensitivity in predicting a positive response to sildenafil (85.9% vs. 70.2% and 92.3% vs. 59.6%, for base and tip rigidity, respectively). Sildenafil response in ED cases can be predicted through NPTR monitoring using the RigiScan device and ED patients with RigiScan base or tip rigidity less than 42% are not expected to respond well to sildenafil.