(121) Validation of a Digital Rigidometer for the Evaluation of Erection Hardness During In-office Rigidity Assessment in Patients with Erectile Dysfunction
Authors: Miranda E , Hallan B , Nascimento B , Paul G , Carneiro F , De Bessa Junior J , Miranda A 
Published: May 2023

Abstract

Introduction
The evaluation of erectile function should include the measurement of axial rigidity, since it is one of the key factors in the pathophysiology, diagnosis and treatment of ED. This assessment is usually performed following in-office intracavernosal injections of vasoactive agents during Doppler ultrasound studies, curvature assessments or simply prior to initiation of intracavernosal pharmacotherapy. In this scenario, the Erectile Hardness Score (EHS) is the most common validated tool to evaluate penile rigidity. Although highly reproducible, EHS is still based on the examiner’s subjective perspective and might eventually lead to conflicting results.

Objective
The aim of the present study was to assess the diagnostic accuracy of a digital rigidometer in comparison to the EHS scale to allow for a more detailed rigidity assessment using an objective measure of penile axial load.

Methods
First we performed a controlled experiment using a digital dynamometer coupled to a 3D-printed tip to assess the maximal load applied to the Pfizer’s Erection Hardness Meter (Figure 1). Three urologists with expertise on the management of ED performed 2 different measures of axial rigidity on each shaft corresponding to the EHS scale in order to suggest a 4-grade classification range. Then, a sample of patients was analyzed during in-office erectile tests performed by 2 different urologists using redosing protocols of vasoactive agents from February to June 2022. Coefficients of variation were calculated using analysis of variance (ANOVA) and t-test was performed to compare the interval data. ROC curves were used to estimate the diagnostic accuracy of the digital rigidometer in comparison to the EHS. P values below 0.05 were considered significant.

Results
Mean axial load supported by each shaft of the Pfizer’s Erection Hardness Meter was: EHS 1: 0.51 ± 0.05 Kg; EHS 2: 0.75 ± 0.05 Kg; EHS 3: 1.2 ± 0.13 Kg; and EHS 4: 2.5 ± 0.51 Kg. The following coefficients of variations were found: EHS 1: 10.1%, EHS 2: 6.85%, EHS 3: 11.2%, and EHS 4: 20.4%. Distribution of different measures is shown in Figure 2. A total of 30 men with mean age of 54.5 ± 15.5 years were included in the analysis. The mean IIEF-EFD was 16.3 ± 5.1. During erection assessment 3 (10%) presented erection EHS 2, 7 (23.3%) EHS 3, and 20 (66.6%) EHS 4. The mean dose of trimix was 0,35 ml and 50% required sympathomimetic medication for erection reversion after the procedure. The digital rigidometer had an AUC of 0.91 (95% CI 0.78-1.00, p=0.0005) to discriminate EHS&gt;3 (Figure 3). The best cuff value for that purpose is 1.2 Kg, yielding a sensitivity of 85.7% and specificity of 88.9%.

Conclusions
The digital rigidometer tested in the present study appears to provide reproducible measures of axial penile rigidity that might be useful in clinical practice. It has demonstrated interesting diagnostic properties for the in-office assessment of erectile rigidity in comparison to the EHS, in which the cutoff of 1.2 Kg is the one with the best diagnostic properties. An objective measurement of penile axial rigidity can contribute to both clinical and research environment.

Disclosure
No