Nocturnal penile erections: the diagnostic value of tumescence and rigidity activity units

One of the most commonly used tests to distinguish psychogenic from organic erectile dysfunction (ED) is to monitor nocturnal penile tumescence using the RigiScan device and its new software called RigiScan Plus. To give a true estimate of the predictive ability of the new RigiScan software parameters, tumescence activity units (TAUs) and rigidity activity units (RAUs), we conducted this study on 639 RigiScan night records of 416 ED patients. For study purposes, these records were transferred to a personal computer and classified as normal and abnormal. We recorded the TAU and RAU provided by the RigiScan software for each event separately and also for the total night. We then estimated the diagnostic performance of these two parameters using cutoff values with highest accuracy plotted against the previously reported normal and abnormal curves. We then made four new calculations to improve the diagnostic accuracy of TAU and RAU for the total night. On estimating the highest diagnostic accuracy of RAU and TAU, it ranged from 67.8 to 73.7% for the single best event and from 68.4 to 74.2% for the total night. When using the newly computed units, the highest diagnostic accuracy did not exceed 75.9%.