Background: Our goal was to show how the
interpretation of the IIEF-5 questionnaire can lead to a significantly different
outcome and propose a modification of the possible responses of the IIEF-5
questionnaire to assess erectile function after transurethral resection of the
prostate (TURP). Methods: The results of patients treated with TURP in a
randomized clinical trial were analyzed under four scenarios characterized by
what patients to include and how to codify the answers for statistical
interpretation: scenario (A) only patients who reported sexual intercourse;
scenario (B) all patients, recording zero response for patients without sexual
activity as one more grade of the scoring scale; scenario (C) same as B but
coding 0 as “99” (missing value); and scenario (D) all patients are included,
but the zero response remains as 0 for patients who reported not having had
sexual intercourse due to the “Inability to penetrate (enter) the partner due to
penile flaccidity”, whereas zero response is coded as “99” in those patients
reporting “Inability to penetrate (enter) the partner due to other causes”.
Results: Eighty-four patients qualified for the analysis. The proportion
of patients in each ED category was very similar among the four scenarios, except
for the “Severe ED” category. At baseline, scenario B had 36.9% of patients
categorized as “Severe ED”, scenario D 18.5%, and scenarios A and C 17.2%
Among the questionnaires available to assess erectile function after transurethral resection of the prostate (TURP), the International Index of Erectile Function 5 (IIEF-5) is one of the most frequently used. The IIEF-5  is an abbreviated five-item version of the IIEF-15 [2, 3, 4], commonly known as the Sexual Health Inventory for Men (SHIM).
Items 1–4 of the IIEF-5 ask about erectile function, and item 5 is related to intercourse satisfaction . Item 1 in the IIEF-5 is a hypothetical question about the patient’s confidence in achieving and maintaining an erection and is scored on a Likert-type scale from 1 to 5. The rest of the items in the IIEF-5 (items 2 to 5) ask about the patient’s experience in the previous weeks and can be scored from 1 to 5 (if the target population is limited to patients who report having had recent sexual intercourse) or from 0 to 5 (if all patients are included, leaving the answer 0 for those not having had recent sexual intercourse) [1, 5]. Whether to include patients without recent sexual intercourse in the questionnaire and how to codify the answer 0 for the statistical analysis is controversial. However, these decisions can profoundly affect the IIEF-5 questionnaire’s accuracy in detecting changes in erectile function and may overestimate the proportion of patients with “Severe erectile dysfunction (ED)” in populations of non-sexually active men, which is expected behavior in the postoperative period of prostate surgery .
The objective of this study was to showcase how the interpretation of the IIEF-5 questionnaire can lead to a significantly different outcome and determine the best way to use the IIEF-5 questionnaire to assess erectile function after transurethral resection of the prostate (TURP). First, we took IIEF-5 scores obtained in a population treated with TURP. Then, we analyzed them under four scenarios (characterized by the different types of patients to include —all or only those sexually active—and the codification of the answers for statistical interpretation).
The study population was retrieved from NCT03936244 randomized clinical trial (RCT), which included men diagnosed with lower urinary tract symptoms (LUTS) in a tertiary-care public institution who required surgical treatment and were randomly allocated to monopolar or plasmakinetic TURP. Additional details on the trial are available in the original publication [7, 8].
IIEF-5 questionnaire scores (Supplementary Table 1) were recorded for all patients at baseline and 1, 3, 6, and 12 months postoperatively . Two additional questions were included at every period: one to capture sexual activity as self-reported by patients (a yes/no question); and another one to capture the reason for sexual inactivity as reported by the patients [possible answers were either “Inability to penetrate (enter) the partner due to penile flaccidity” or “Other causes (e.g., lack of sexual desire, lack of a sexual partner, etc.)”]. The severity of ED was established in five categories: “Severe ED” (1–7 points), “Moderate ED” (8–11 points), “Mild to moderate ED” (12–16 points), “Mild ED” (17–21 points), and “Without of ED” (22–25 points).
For the purposes of this analysis, all patients from the RCT were jointly analyzed, regardless of the surgical technique used. We created four different analytical scenarios, named from A to D, that differ on the patients included (all or only those sexually active), the inclusion of answer 0 in IIEF-5 items 2–5 for patients without sexual activity, and the statistical coding of the response 0 (Table 1 and Supplementary Table 2).
|Scenario A||Scenario B||Scenario C||Scenario D|
|Patients with sexual activity||YES||YES||YES||YES|
|Patients without sexual activity due to “Inability to penetrate (enter) the partner due to penile flaccidity”||NO||YES||YES||YES|
|Answer 0 coded as 0||Answer 0 coded as 99||Answer 0 coded as 0|
|Patients without sexual activity due to “Other causes”||NO||YES||YES||YES|
|Answer 0 coded as 0||Answer 0 coded as 99||Answer 0 coded as 99|
Total IIEF-5 score and ED categories were only calculated for patients with no missing values (ergo, missing values were coded as “99”) in the four scenarios.
In summary, only patients with sexual activity are included in scenario A, and in scenarios B, C, and D, all patients are included. Additionally, in scenarios B, C, and D, the codification of items 2–5 follows Table 1 (Supplementary Table 2).
Nominal variables were described with absolute numbers and percentages.
Quantitative variables with the mean and standard deviation. Severity grades of
ED were plotted with clustered bar graphs. Comparisons were conducted using the
chi-square test. Statistical significance was established at p
Eighty-four patients were counted in the analysis. Table 2 shows the proportion of men sexually active on each clinical visit. It is patent that there was a significant decrease in the proportion of patients who manifested having sexual intercourse at one month compared to the baseline (53.6% vs. 76.2%), reaching almost pre-surgical values at three months and remaining stable afterward (71.4%, 70.2%, and 70.2% at 3, 6, and 12 months, respectively). Furthermore, we observe that the increase in patients without sexual activity in the first month corresponds to “Other causes (e.g., lack of sexual desire, lack of a sexual partner, etc.)”, whereas the percentage of patients who did not have sexual activity due to the “Inability to penetrate the partner” remained stable over time (between 11.9% and 15.5%). Finally, it is essential to note that the study protocol did not prescribe sexual abstinence, which means that the decrease in the proportion of patients who had sexual activity during the first postoperative month corresponds exclusively to the patients’ own decisions.
|Baseline||1 mo||3 mo||6 mo||12 mo|
|(n = 84)||(n = 84)||(n = 84)||(n = 84)||(n = 84)|
|Sexually active, n (%)||64 (76.2)||45 (53.6)||60 (71.4)||59 (70.2)||59 (70.2)|
|Reason for sexual inactivity n (%)||Inability to penetrate (enter) the partner due to penile flaccidity||10 (11.9)||11 (13.1)||12 (14.3)||13 (15.5)||11 (13.1)|
|Other causes (e.g., lack of sexual desire, lack of a sexual partner, etc.)||10 (11.9)||28 (33.3)||12 (14.3)||12 (14.3)||14 (16.7)|
Regarding the four aforementioned scenarios, the score of IIEF-5 item 1 at baseline was equal in scenarios B, C, and D and lower than scenario A (2.2 vs. 2.4 points, respectively) (Table 3); This difference remained constant in all postoperative visits. The score of IIEF-5 items 2–5 is the same in scenarios A and C, lower in scenario D, and even lower in scenario B; this is true for baseline and the consecutive clinical visits (Table 3). The same applies to the total IIEF-5 score, which was 14.2, 11.2, and 10.1 points at baseline for scenarios A and C, D, and B, respectively (Table 3).
|IIEF-5 score||Scenario A||Scenario B||Scenario C||Scenario D|
|Item 1, points||2.4
|Item 2, points||2.8
|Item 3, points||2.6
|Item 4, points||3.1
|Item 5, points||3.2
|Item 1, points||2.6
|Item 2, points||3.1
|Item 3, points||2.8
|Item 4, points||3.3
|Item 5, points||3.3
|Item 1, points||2.5
|Item 2, points||2.8
|Item 3, points||2.5
|Item 4, points||2.9
|Item 5, points||3.1
|Item 1, points||2.7
|Item 2, points||3.2
|Item 3, points||3.1
|Item 4, points||3.4
|Item 5, points||3.5
|Item 1, points||2.6
|Item 2, points||2.9
|Item 3, points||2.8
|Item 4, points||3
|Item 5, points||3
|Abbreviations: IIEF, International Index of Erectile Function; mo, month; SD, standard deviation.|
Except for the “Severe ED” category, the proportion of patients allocated in each of the remaining ED categories was the same in scenarios A and C, lower in scenario D, and even lower in scenario B: both at baseline and in the consecutive clinical visits (Table 4, Fig. 1). The proportion of patients with “Severe ED” in each scenario behaves in the opposite way than the rest of the categories. As an example, in the first postoperative month, the proportions of patients categorized as “Mild ED” in scenarios A and C, D and B were 29.7%, 25.7%, and 22.6%, whereas the proportions of patients categorized as “Severe ED” in the same scenarios were 20.0%, 35.7%, and 57.1%, respectively. As expected, differences between the scenarios are only statistically significant in the “Severe ED” category for all clinical visits.
Severe erectile disfunction throughout follow-up. The chart represents the percentage of patients allocated to the “severe erectile dysfunction (ED)” category based on the total IIEF-5 score in each postulated scenario.
|IIEF-5 categories||Scenario A||Scenario B||Scenario C||Scenario D||p-value|
|n (%)||n (%)||n (%)||n (%)||n (%)|
|Without ED||7 (10.9)||7 (8.3)||7 (10.9)||7 (9.5)||0.940|
|Mild ED||19 (29.7)||19 (22.6)||19 (29.7)||19 (25.7)||0.720|
|Mild-moderate ED||11 (17.2)||11 (13.1)||11 (17.2)||11 (14.9)||0.879|
|Moderate ED||16 (25.0)||16 (19.0)||16 (25.0)||16 (21.6)||0.785|
|Severe ED||11 (17.2)||31 (36.9)||11 (17.2)||21 (28.4)||0.014|
|Without ED||6 (13.3)||6 (7.1)||6 (13.3)||6 (10.7)||0.618|
|Mild ED||17 (37.8)||17 (20.2)||17 (37.8)||17 (30.4)||0.092|
|Mild-moderate ED||8 (17.8)||8 (9.5)||8 (17.8)||8 (14.3)||0.479|
|Moderate ED||5 (11.1)||5 (6.0)||5 (11.1)||5 (8.9)||0.691|
|Severe ED||9 (20.0)||48 (57.1)||9 (20.0)||20 (35.7)|
|Without ED||14 (23.3)||14 (16.7)||14 (23.3)||14 (20.0)||0.715|
|Mild ED||8 (13.3)||8 (9.5)||8 (13.3)||8 (11.4)||0.873|
|Mild-moderate ED||14 (23.3)||14 (16.7)||14 (23.3)||14 (20.0)||0.715|
|Moderate ED||7 (11.7)||7 (8.3)||7 (11.7)||7 (10.0)||0.896|
|Severe ED||17 (28.3)||41 (48.8)||17 (28.3)||27 (38.6)||0.030|
|Without ED||14 (23.7)||14 (16.7)||14 (23.7)||14 (20.0)||0.678|
|Mild ED||16 (27.1)||16 (19.0)||16 (27.1)||16 (22.9)||0.615|
|Mild-moderate ED||10 (16.9)||10 (11.9)||10 (16.9)||10 (14.3)||0.799|
|Moderate ED||12 (20.3)||12 (14.3)||12 (20.3)||12 (17.1)||0.740|
|Severe ED||7 (11.9)||32 (38.1)||7 (11.9)||18 (25.7)|
|Without ED||12 (20.3)||12 (14.3)||12 (20.3)||12 (17.1)||0.74|
|Mild ED||15 (25.4)||15 (17.9)||15 (25.4)||15 (21.4)||0.647|
|Mild-moderate ED||9 (15.3)||9 (10.7)||9 (15.3)||9 (12.9)||0.827|
|Moderate ED||7 (11.9)||7 (8.3)||7 (11.9)||7 (10.0)||0.880|
|Severe ED||16 (27.1)||41 (48.8)||16 (27.1)||27 (38.6)||0.018|
|Abbreviations: ED, erectile dysfunction; IIEF, International Index of Erectile Function; mo, month; n, number of patients.|
Urologists well know the IIEF-5 questionnaire, and its use is widespread worldwide. However, its interpretation is neither easy nor standardized. In this regard, the interpretation of the IIEF-5 questionnaire scores to assess erectile function after TURP may significantly impact the determination of the proportion of “Severe ED”. Creating these four scenarios helps understand how each interpretation influences the results and what scenario provides the most accurate evaluation.
Some authors recommend removing the zero-category in all IIEF-5 items and using the questionnaire exclusively in patients who report sexual intercourse (like in our scenario A) to improve the accuracy in estimating the prevalence of ED . We concur that this is a good step to avoid the “false positives” of patients tagged as suffering “Severe ED” when all lack of sexual activity is coded as zero (like in our scenario B). This is reasonable because, apart from suffering from ED, there are many other reasons why a man might not be engaging in sexual activity.
However, we consider that in the TURP postoperative population, it leads to a significant “Severe ED” underestimation bias because it does not allow the analysis of erectile function in patients without sexual intercourse, a commonplace event in this population. In our study, we asked the patients to determine the reason for the lack of sexual activity. As shown in Table 3, it was distributed approximately halfway between the “Inability to penetrate the partner” and “Other causes”, except for the first postoperative month. In the first postoperative month, the reasons unrelated to ED increased significantly (71.8% vs. 28.2%), driven by the patient’s own decision.
When 0 response in items 2–5 is included but coded as a missing value (scenario C), it is possible to get complete information in patients with sexual intercourse (IIEF-5 items 1–5) and partial information in patients without sexual intercourse (IIEF-5 item 1). This scenario is a minor improvement from scenario A because it avoids the “false positives” of patients tagged as suffering “Severe ED” and helps further characterize the sexual function of patients without sexual activity via the answer to item 1. However, scenario C does not improve the statistical calculation of the “Severe ED” rate.
We consider that scenario D is a further improvement from scenario C because it allows including in the statistical analysis the patients who self-reported not having had sexual activity due to the “Inability to penetrate (enter) the partner due to penile flaccidity”. Although we are aware that the “Inability to penetrate (enter) the partner due to penile flaccidity” is not a confirmed diagnosis of “Severe ED”, we believe that it provides the best accuracy in evaluating the effect on the erectile function of a surgical technique. In conclusion, according to these results, scenario D should be the most appropriate for patients undergoing TURP.
Another way to gather the information necessary to execute scenario D, instead of having a separate question to determine the cause of the lack of sexual activity, would be to provide two additional possible answers (option 0 and 99) in items 2 to 5 of the IIEF-5. As an example, the possible answers to item 2 of the IIEF-5 questionnaire would be:
Assuming that scenario D is the one that best estimates the proportion of patients with severe ED, we found an underestimation of “Severe ED” from 10.3% to 15.7% in scenarios A and C during follow-up and an overestimation from 8.5 to 21.4% in scenario B (Fig. 2).
Differences in the proportion of patients with “severe erectile dysfunction”. Taking Scenario D as a reference, the chart represents the difference in the rate of “severe erectile dysfunction (ED)” obtained in the other scenarios. Positive differences indicate a potential overestimation of “Severe ED”, and negative differences a potential underestimation.
The present manuscript is a proposal for modifying the possible responses of the IIEF-5 questionnaire in the postoperative period of patients undergoing TURP and, by extension, in all surgeries where a decrease in sexual activity is expected for a cause other than severe ED. Nonetheless, prospective studies and adequate psychometric validation are necessary before widespread use.
The different options on how to interpret IIEF-5 questionnaire scores to assess erectile function after TURP may have a significant impact on determining the degree of “Severe ED”. Questionnaires without response 0 should be used exclusively in patients with sexual activity. When using questionnaires with option 0, an adequate statistical interpretation is necessary to avoid overestimating “Severe ED”. Using questionnaires with options 0 and 99 (as defined in scenario D) may improve the accuracy of detecting patients with “Severe ED” in the postoperative period of TURP.
ED, erectile dysfunction; IIEF-5, international index of erectile function 5; LUTS, lower urinary tract symptoms; NA, not applicable; RCT, randomized clinical trial; SD, standard deviation; SHIM, sexual health inventory for men; TURP, transurethral resection of the prostate.
Study Design: HOA. Data Collection: HOA, AECC. Data Analysis: HOA, CNT, FJOM. Writing Original Draft: HOA. Manuscript Review and Editing: HOA, AECC, CNT, FJOM. All authors contributed to editorial changes in the manuscript. All authors read and approved the final manuscript.
Ethical approval of the institutional review board (IRB) (APR-14-72) was granted, and informed consent was obtained from all subjects. Clinical Trial Registration: NCT03936244 (https://clinicaltrials.gov/ct2/show/NCT03936244).
The authors express their acknowledgments to Santiago Otaola because of his invaluable support.
This research received no external funding.
The authors declare no conflict of interest.
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