Audiovisual Sexual Stimulation and RigiScan Test for the Diagnosis of Erectile Dysfunction.

BACKGROUND: Currently available evaluation criteria for penile tumescence and rigidity have been fraught with controversy. In this study, we sought to establish normative Chinese evaluation criteria for penile tumescence and rigidity by utilizing audiovisual sexual stimulation and RigiScan™ test (AVSS-Rigiscan test) with the administration of phosphodiesterase-5 inhibitor.
METHODS: A total of 1169 patients (aged 18-67 years) complained of erectile dysfunction (ED) underwent AVSS-RigiScan test with the administration of phosphodiesterase-5 inhibitor. A total of 1078 patients whose final etiological diagnosis was accurate by means of history, endocrine, vascular, and neurological diagnosis, International Index of Erectile Function 5 questionnaire, and erection hardness score were included in the research. Logistic regression model and receiver operating characteristic curve analysis were performed to determine the cutoff value of the RigiScan™ data. Then, the multivariable logistic analysis was used in the selected variables.
RESULTS: A normal result is defined as one erection with basal rigidity over 60% sustained for at least 8.75 min, average event rigidity of tip at least 43.5% and base at least 50.5%, average maximum rigidity of tip at least 62.5% and base at least 67.5%, △tumescence (increase of tumescence or maximum-minimum tumescence) of tip at least 1.75 cm and base at least 1.95 cm, total tumescence time at least 29.75 min, and times of total tumescence at least once. Most importantly, basal rigidity over 60% sustained for at least 8.75 min, average event rigidity of tip at least 43.5%, and base at least 50.5% would be the new normative Chinese evaluation criteria for penile tumescence and rigidity. By multivariable logistic regression analysis, six significant RigiScan™ parameters including times of total tumescence, duration of erectile episodes over 60%, average event rigidity of tip, △tumescence of tip, average event rigidity of base, and △tumescence of base contribute to the risk model of ED. In logistic regression equation, predict value P < 0.303 was considered as psychogenic ED. The sensitivity and specificity of the AVSS-RigiScan test with the administration of phosphodiesterase-5 inhibitor in discriminating psychogenic from organic ED was 87.7% and 93.4%, respectively.
CONCLUSIONS: This study suggests that AVSS-RigiScan test with oral phosphodiesterase-5 inhibitors can objectively assess penile tumescence and rigidity and seems to be a better modality in differentiating psychogenic from organic ED. However, due to the limited sample size, bias cannot be totally excluded.

INTRODUCTION

Penile erection is a complex event controlled by vascular, hormonal, and neurological systems.[1] Depending on the context in which penile erection occurs, it is generally accepted that different central and peripheral neural and/or humoral endocrine mechanisms may participate in the regulation of this sexual response, often in a very complex fashion.[234] Erectile dysfunction (ED) is a men's health issue that is receiving overwhelming attention in recent years. Although studies have shown that up to 52% of the male population aged 40–70 years had different degrees of ED, data from the National Health and Social Life Survey had found that only about 1 in 10 men with ED between 18 and 59 years of age actually went to a physician for consultation regarding their sexual dysfunction.[567] Currently, the diagnostic application of RigiScan™ in nocturnal penile tumescence and rigidity (NPTR) is well recognized as an available powerful means to discriminate between psychogenic and organic ED,[891011] and it takes a time- and money-consuming effort to obtain the nocturnal erectile activity.[12] In addition, normal values of NPTR parameters are controversial for researchers and normative data for RigiScan™ are in urgent need.[1113] Therefore, currently available evaluation criteria for NPTR test should be revised, and a brand new approach for RigiScan™ test needs developing.

Nowadays, audiovisual sexual stimulation and RigiScan™ (AVSS-RigiScan) is widely regarded as a more useful tool than NPT-RigiScan for diagnosis and antidiastole of ED.[121415] Sexually induced erections and sleep erections are not the same. Sexually induced erections are a combination of erotic and reflex erection activity, whereas the mechanism initiating and maintaining sleep erections still remains unknown.[16] The difference between sleep and sexually induced erections is primarily neurological. Both erections involve the same vascular and penile structural components. In addition, AVSS-RigiScan test is relatively simple, cost-effective, and less time-consuming. There have been remarkably few studies evaluating AVSS-RigiScan in healthy aging men. This study aimed not only to establish normative Chinese evaluation criteria for future studies of men with ED, but also to reevaluate the significance of RigiScan™ Plus in the diagnosis of ED by utilizing AVSS-RigiScan test with the administration of phosphodiesterase-5 inhibitor.

METHODS

Ethical approval

All methods were carried out in accordance with the guidelines, and study protocol approved by the Institutional Review Board and written informed consent was obtained from all participants that participated in the study.

Participants

Between 2008 and 2012, a total of 1169 patients aged 18–67 years (mean ± standard deviation, 30.3 ± 7.9 years) complained of ED for at least 6 months who were not excessively exposed to AVSS, or not super-suppressed, or not easily affected by the test circumstances, or had no contraindications for phosphodiesterase-5 inhibitors underwent AVSS-RigiScan test with administration of 20 mg of vardenafil. A total of 1078 patients whose final etiological diagnosis was accurate were included in the research, whereas 91 patients who were resistant to the test (n = 16) or failed to be followed up (n = 75) were excluded from the study.

Baseline evaluation

Our clinical guideline for the evaluation of ED is as follows: sexual history, physical examination, and analysis of serum glucose level. Each participant completed a self-reported assessment of erectile function using the erectile domain section of the International Index of Erectile Function 5 (IIEF-5) questionnaire and erection hardness score. Laboratory data (biochemical profile, complete blood count, and urinalysis) and serum concentrations of total testosterone, luteinizing hormone, follicle-stimulating hormone, prolactin, and estradiol were taken (data not shown).

Audiovisual sexual stimulation test

Twenty milligrams of vardenafil was administrated to all patients. One hour after administration of 20 mg of vardenafil, patients were then asked to lie in a supine position on a comfortable examination table. The examination room was dimly lit for comfort. The penis of the patient was connected to the RigiScan™ Plus device according to the instruction manual, and the device automatically determined the baseline penile rigidity and tumescence for the first 15 min. An audiovisual headset was placed on the participant's head and adjusted to a comfortable volume. The 60 min erotic video was shown individually to each patient in a dark and silent room and then stimulated rigidity and tumescence for the next 60 min. In this study, manual stimulation of the penis was prohibited during the session.

Etiological diagnosis of erectile dysfunction

In the following day, all patients were evaluated with intracavernous injection (ICI). If this result is abnormal, we continue evaluation with penile color flow Doppler ultrasonography (PDU) and cavernosometry-cavernosography and neurological tests in selected cases to differentiate psychogenic ED from vascular ED. Psychogenic ED is defined as IIEF-5 <21 and no evidence of endocrine, vascular, and neurological system disorders and erectile angle >90° after ICI sustained for at least 30 min. Organic ED is defined as IIEF-5 <21 and erectile angle <90° after ICI sustained for <30 min or evidence of endocrine, penile vascular, and neurological system disorders or diabetes mellitus. All the methods utilized to make etiological diagnosis of ED are routine and authorized methods for ED diagnosis, and the experimental protocols are also conventional ones.

Statistical analysis

Data analysis was performed with SPSS version 17.0 for Windows (SPSS Inc., Chicago, IL, USA). Wilcoxon rank sum test was performed on parameters between psychogenic and organic ED; Kruskal-Wallis H-test was used in parameters with regard to etiological groups and age groups. Logistic regression model and receiver operating characteristic (ROC) curve analysis were performed on the RigiScan™ data with final etiological diagnosis as the outcome. Then, multivariable logistic analysis was used in the selected variables. Two-sided P < 0.05 was considered to be statistically significant.

RESULTS

Participants' profile

All patients were evaluated with ICI, PDU, and cavernosometry-cavernosography and neurological tests in selected cases. The final diagnosis was psychogenic ED in 743 patients (68.9%), whereas 335 patients (31.1%) were found to have organic ED. In the 743 patients diagnosed with psychogenic ED, 17 patients were false positives. Of the 335 patients diagnosed with organic ED, two patients were false negatives, 242 patients (72.2%) were diagnosed with vascular ED, and 45 patients (13.4%) were diagnosed with endocrine ED. AVSS-RigiScan parameters with regard to etiology and age are shown in Tables 1–3. Parameters except for times of total tumescence between psychogenic and organic ED were statistically significant (P < 0.05). Parameters with regard to etiological groups, average event rigidity of tip (%), duration of erectile episodes over 60% (min), and average event rigidity of base (%) were statistically significant (P < 0.05). Parameters with regard to age groups, average maximum rigidity of tip (%), and average maximum rigidity of base (%) were statistically significant (P < 0.05).

Table 1

Parameters of AVSS-RigiScan test with the administration of phosphodiesterase-5 inhibitor between psychogenic and organic erectile dysfunction patients

Parameters	Psychogenic ED (n = 743)	Organic ED (n = 335)	Wilcoxon W	P
Average event rigidity of tip (%)	52.00 (9.00)	27.00 (16.00)	16,571.50	<0.001
Duration of erectile episodes over 60% (min)	21.00 (20.00)	0.00 (5.00)	16,601.00	<0.001
Average event rigidity of base (%)	58.00 (9.00)	35.00 (17.00)	17,156.00	<0.001
Average maximum rigidity of tip (%)	71.00 (9.00)	53.00 (21.00)	20,517.00	<0.001
Average maximum rigidity of base (%)	75.00 (9.00)	58.00 (18.00)	21,308.00	<0.001
∆Tumescence of tip (cm)	2.00 (0.60)	1.60 (0.70)	24,709.50	<0.001
∆Tumescence of base (cm)	2.30 (0.60)	1.80 (0.63)	26,525.50	<0.001
Times of erectile episodes over 60%	1.00 (0.00)	0.00 (1.00)	27,958.50	<0.001
Total tumescence time (min)	40.75 (20.00)	22.75 (25.50)	28,316.50	<0.001
Times of total tumescence	1.00 (0.00)	1.00 (0.00)	41,059.00	0.172

Data are shown as median (interquartile range). ∆Tumescence: increase of tumescence or maximum−minimum tumescence. ED: Erectile dysfunction; AVSS: Audiovisual sexual stimulation.

Table 3

AVSS-RigiScan test parameters with regard to age groups of erectile dysfunction patients

Parameters	≤29 years (n = 634)	30–39 years (n = 306)	40–49 years (n = 107)	≥50 years (n = 31)	Kruskal-Wallis H	P
Average event rigidity of tip (%)	48.00 (20.00)	47.00 (18.00)	40.00 (30.00)	47.00 (24.00)	5.87	0.118
Duration of erectile episodes over 60% (min)	15.00 (24.00)	13.00 (21.00)	7.75 (24.00)	15.00 (36.00)	3.64	0.303
Average event rigidity of base (%)	55.00 (16.00)	53.00 (17.00)	49.50 (24.00)	53.00 (29.00)	5.21	0.157
Average maximum rigidity of tip (%)	69.00 (15.00)	67.00 (14.00)	67.00 (27.00)	65.00 (26.00)	9.95	0.019
Average maximum rigidity of base (%)	73.00 (15.00)	73.00 (14.00)	69.50 (17.00)	69.00 (25.00)	8.18	0.042
∆Tumescence of tip (cm)	1.90 (0.65)	1.90 (0.75)	1.90 (0.58)	1.70 (0.55)	4.91	0.179
∆Tumescence of base (cm)	2.20 (0.70)	2.20 (0.70)	2.20 (0.75)	2.20 (0.55)	2.46	0.482
Times of erectile episodes over 60%	1.00 (0.00)	1.00 (0.00)	1.00 (1.00)	1.00 (1.00)	6.16	0.104
Total tumescence time (min)	37.00 (22.13)	36.00 (27.75)	33.50 (30.25)	38.00 (40.13)	0.83	0.841
Times of total tumescence	1.00 (0.00)	1.00 (0.00)	1.00 (0.00)	1.00 (0.00)	2.49	0.477

Data are shown as median (interquartile range). ∆Tumescence: increase of tumescence or maximum−minimum tumescence. AVSS: Audiovisual sexual stimulation.

Relationship between parameters and the diagnosis of erectile dysfunction

Area under the curve (AUC) of RigiScan™ parameters screened by logistic regression analysis were listed as the following order: average event rigidity of tip (AUC = 0.943, P = 0.001) > duration of erectile episodes over 60% (AUC = 0.942, P = 0.001) > average event rigidity of base (AUC = 0.933, P = 0.001) > average maximum rigidity of tip (AUC = 0.876, P = 0.001) > average maximum rigidity of base (AUC = 0.862, P = 0.001) > △tumescence (increase of tumescence or maximum−minimum tumescence) of tip (AUC = 0.804, P = 0.001) > △tumescence of base (AUC = 0.773, P = 0.001) > times of erectile episodes over 60% (AUC = 0.749, P = 0.001) > total tumescence time (AUC = 0.743, P = 0.001) > times of total tumescence (AUC = 0.526, P = 0.335) [Table 4 and Figure 1].

Table 4

Area under the curves for different parameters of AVSS-RigiScan test with the administration of phosphodiesterase-5 inhibitor

Parameters	AUC	SE	95% confidence interval	P
Average event rigidity of tip (%)	0.943	0.010	0.923-0.963	<0.001
Duration of erectile episodes over 60% (min)	0.942	0.010	0.922-0.963	<0.001
Average event rigidity of base (%)	0.933	0.011	0.910-0.955	<0.001
Average maximum rigidity of tip (%)	0.876	0.018	0.840-0.912	<0.001
Average maximum rigidity of base (%)	0.862	0.019	0.825-0.900	<0.001
∆Tumescence of tip (cm)	0.804	0.022	0.762-0.847	<0.001
∆Tumescence of base (cm)	0.773	0.023	0.728-0.819	<0.001
Times of erectile episodes over 60%	0.749	0.026	0.697-0.801	<0.001
Total tumescence time (min)	0.743	0.024	0.695-0.791	<0.001
Times of total tumescence	0.526	0.027	0.474-0.579	0.335

∆Tumescence: increase of tumescence or maximum−minimum tumescence. AUC: Area under the curve; SE: Standard error; AVSS: Audiovisual sexual stimulation.

Figure 1

Receiver operating characteristic analyses for different parameters of AVSS-RigiScan test with the administration of phosphodiesterase-5 inhibitor in erectile dysfunction patients. (a) Average event rigidity of tip (%). (b) Duration of erectile episodes over 60% (min). (c) Average event rigidity of base (%). (d) Average maximum rigidity of tip (%). (e) Average maximum rigidity of base (%). (f) ΔTumescence of tip (cm). (g) ΔTumescence of base (cm). (h) Times of erectile episodes over 60%. (i) Total tumescence time(min). ΔTumescence: increase of tumescence or maximum−minimum tumescence. AVSS: Audiovisual sexual stimulation.

Normative values for penile rigidity

According to AUC and Max(Sensitivity + Specificity), normative AVSS-RigiScan parameters (duration of erectile episodes over 60%, average event rigidity of tip, average event rigidity of base, average maximum rigidity of tip, average maximum rigidity of base, △tumescence of tip, △tumescence of base, and total tumescence time) are summarized in Table 5.

Table 5

Normative value for parameters of AVSS-RigiScan test with the administration of phosphodiesterase-5 inhibitor

Parameters	Value	Sensitivity	Specificity	Max(Sensitivity + Specificity)
Average event rigidity of tip (%)	43.500	0.938	0.840	1.778
Duration of erectile episodes over 60% (min)	8.750	0.926	0.848	1.774
Average event rigidity of base (%)	50.500	0.938	0.818	1.756
Average maximum rigidity of tip (%)	62.500	0.778	0.851	1.629
Average maximum rigidity of base (%)	67.500	0.778	0.837	1.615
∆Tumescence of tip (cm)	1.750	0.698	0.796	1.494
∆Tumescence of base (cm)	1.950	0.580	0.862	1.442
Times of erectile episodes over 60%	1.000	0.119	0.882	0.938
Total tumescence time (min)	29.750	0.636	0.780	1.416
Times of total tumescence	1.000	0.827	0.223	1.050

∆Tumescence: increase of tumescence or maximum−minimum tumescence; AVSS: Audiovisual sexual stimulation.

Establishment of risk model of erectile dysfunction

By multivariable logistic regression analysis, it was revealed that there were six significant AVSS-RigiScan parameters (P < 0.05) for differentiating psychogenic ED from organic ED as times of total tumescence, duration of erectile episodes over 60%, average event rigidity of tip, △tumescence of tip, average event rigidity of base, and △tumescence of base [Table 6]. Logistic regression equation (area under the curve=0.967) was as following: P = 1/1 + Exp (− [3.457 + 0.052X3 −0.309X5 −0.212X7 +1.059X8 +0.149X9 −1.944X10]). ROC analysis produced a cutoff value (0.303) with a sensitivity of 87.7% and a specificity of 93.4% for ED diagnosis, that is, organic ED was considered with a predict value of P ≥ 0.303, whereas the predict value of P < 0.303 was considered as psychogenic ED [Figure 2].

Table 6

Multivariable logistic analysis for parameters of AVSS-RigiScan test with the administration of phosphodiesterase-5 inhibitor

Variables	Regression coefficient (βj)	P	OR
Age (X1)	0.016	0.530	1.016
Marital status (X2)	0.393	0.319	1.481
Total tumescence time (X3)	0.052	0.001	1.053
Times of total tumescence (X4)	−0.610	0.068	0.543
Duration of erectile episodes over 60% (X5)	−0.309	<0.001	0.734
Times of erectile episodes over 60% (X6)	−0.254	0.484	0.776
Average event rigidity of base (X7)	−0.212	0.000	0.809
∆Tumescence of tip (X8)	1.059	0.032	2.884
Average maximum rigidity of base (X9)	0.149	0.001	1.161
∆Tumescence of base (X10)	−1.944	0.000	0.143
Average maximum rigidity of tip (X11)	0.029	0.424	1.029
Average maximum rigidity of base (X12)	−0.015	0.678	0.985
Constant	3.457	0.015	31.718

∆Tumescence: increase of tumescence or maximum−minimum tumescence. OR: Odds ratio; AVSS: Audiovisual sexual stimulation.

Figure 2

Receiver operating characteristic analysis for logistic regression equation (AUC=0.967). The regression equation was composed of total tumescence time (X3), duration of erectile episodes over 60% (X5), average event rigidity of base (X7), Δtumescence of tip (X8), average maximum rigidity of base (X9), and Δtumescence of base (X10) by AVSS-Rigiscan test in erectile dysfunction patients: P = 1/1 + Exp (− [3.457 + 0.052X3 − 0.309X5 − 0.212X7 + 1.059X8 + 0.149X9 − 1.944X10]). ΔTumescence: increase of tumescence or maximum−minimum tumescence; AVSS: Audiovisual sexual stimulation; AUC: Area under the curve.

DISCUSSION

In the era of pharmacotherapy for ED, it is important for the clinician to differentiate psychogenic ED from organic ED in planning treatment modalities. Recently, AVSS is more commonly used than NPT because the tumescence during AVSS is more similar to that during sexual intercourse.[14151617] In addition, the test is relatively simple, cost-effective, less time-consuming, and more physiologic than the NPT. However, the test for erection relies on psychogenic stimulation, if a subject with normal erection who is excessively exposed to AVSS, or super-suppressed, or easily affected by the test circumstances would fail to response and measurement value would lose.[1214] Thereby the method that patients were given with three-dimensional AVSS and phosphodiesterase-5 inhibitor will not just avoid or reduce the defects of the conventional AVSS and but improve the diagnostic performance of AVSS.[121415181920]

There have been remarkably few studies that have evaluated AVSS-RigiScan in healthy aging men. However, currently available evaluation criteria for penile tumescence and rigidity have been very controversial.[1321] In this study, we sought not ony to establish normative Chinese evaluation criteria for future studies of men with ED but also to reevaluate the significance of RigiScan™ Plus in the diagnosis of ED by utilizing AVSS-RigiScan test with the administration of 20 mg of vardenafil. All the patients whose final etiological diagnosis was accurate by means of history, endocrine, vascular, and neurological diagnostic techniques were included in the study. The final diagnosis was psychogenic ED in 68.9%, whereas 31.1% patients were found to have organic ED. Of the patients diagnosed with organic ED, most patients (72.2%) were diagnosed with vascular ED.

Among all RigiScan™ parameters, other than times of total tumescence, these parameters (average event rigidity of tip [%], duration of erectile episodes over 60% [min], average event rigidity of base [%], average maximum rigidity of tip [%], average maximum rigidity of base [%], △tumescence of tip [cm], △tumescence of base [cm], times of erectile episodes over 60%, and total tumescence time [min]) were observed statistically significant difference. AUC of RigiScan™ parameters screened by logistic regression analysis revealed the following order: average event rigidity of tip > duration of erectile episodes over 60% > average event rigidity of base > average maximum rigidity of tip > average maximum rigidity of base > △tumescence of tip > △tumescence of base > times of erectile episodes over 60% > total tumescence time > times of total tumescence. A normal result is defined as one erection with base rigidity over 60% sustained for at least 8.75 min, average event rigidity of tip at least 43.5% and base at least 50.5%, average maximum rigidity of tip at least 62.5% and base at least 67.5%, △tumescence of tip at least 1.75 cm and base at least 1.95 cm, total tumescence time at least 29.75 min, and times of total tumescence at least once. Most importantly, base rigidity over 60% sustained for at least 8.75 min, average event rigidity of tip at least 43.5%, and base at least 50.5% would be the new normative Chinese evaluation criteria for penile tumescence and rigidity.

By multivariable logistic regression analysis, six significant RigiScan™ parameters including times of total tumescence, duration of erectile episodes over 60%, average event rigidity of tip, △tumescence of tip, average event rigidity of base, and △tumescence of base contribute to the risk model of ED. It was revealed that the sensitivity and specificity of the AVSS-RigiScan test with the administration of phosphodiesterase-5 inhibitor in discriminating psychogenic from organic ED was 87.7% and 93.4%, respectively.

This study suggests that AVSS-RigiScan test with oral phosphodiesterase-5 inhibitors can objectively assess penile tumescence and rigidity and seems to be a better modality in differentiating psychogenic from organic ED. We anticipate that application of these criteria for AVSS-RigiScan will improve the diagnostic validity of ED. Since the size of this study and the population of ED patients were limited, bias cannot be totally excluded. Future research will determine whether these criteria are too strict for the evaluation of ED. Thereby, a multicenter clinical study on the diagnostic criteria for ED is urgently needed in China.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

Table 2

AVSS-RigiScan test parameters with regard to etiological groups of organic erectile dysfunction

Parameters	Neurogenic ED (n = 25)	Vascular ED (n = 242)	Endocrine ED (n = 45)	Others (n = 23)	Kruskal-Wallis H	P
Average event rigidity of tip (%)	40.50 (31.00)	29.00 (24.00)	45.00 (27.00)	29.00 (8.00)	12.13	0.007
Duration of erectile episodes over 60% (min)	10.75 (25.00)	2.00 (54.00)	5.75 (33.00)	2.00 (7.00)	13.25	0.004
Average event rigidity of base (%)	46.50 (27.00)	39.00 (22.00)	50.50 (29.00)	39.00 (14.00)	12.73	0.005
Average maximum rigidity of tip (%)	63.00 (25.00)	55.00 (25.00)	62.00 (23.75)	62.00 (23.00)	6.81	0.078
Average maximum rigidity of base (%)	69.00 (20.75)	62.00 (22.00)	70.00 (21.00)	64.00 (17.00)	7.51	0.057
∆Tumescence of tip (cm)	1.85 (0.85)	1.70 (0.80)	1.70 (0.65)	1.60 (0.70)	5.46	0.141
∆Tumescence of base (cm)	2.10 (0.67)	2.00 (0.70)	2.05 (0.70)	2.00 (0.60)	0.95	0.815
Times of erectile episodes over 60%	10.75 (25.00)	2.00 (9.00)	5.75 (33.00)	2.00 (7.00)	4.28	0.233
Total tumescence time (min)	31.00 (34.25)	28.00 (28.00)	32.50 (33.38)	22.00 (18.50)	3.10	0.377
Times of total tumescence	1.00 (0.00)	1.00 (0.00)	1.00 (0.00)	1.00 (1.00)	2.93	0.403

Data are shown as median (interquartile range). ∆Tumescence: increase of tumescence or maximum−minimum tumescence. ED: Erectile dysfunction; AVSS: Audiovisual sexual stimulation.