Proper use of the International Index of Erectile Function 5 (IIEF-5) Questionnaire in patients undergoing Transurethral Resection of the Prostate (TURP)

Abstract

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% (p < 0.01). This relative order remained constant in all postoperative visits. The differences in “Severe ED” rates were directly correlated with the inclusion of patients without sexual activity (higher “Severe ED” rate) and the codification of zero responses (when left as zero, they increase “Severe ED” rate, whereas when coded as 99 they are not included in the analysis and “Severe ED” rates decrease). Taking scenario D as a reference, we found a significant overestimation of “Severe ED” in scenario B up to 21.4% and a slight underestimation in scenarios A and B up to –15.7%. Conclusions: Using the IIEF-5 questionnaire with options 0 and 99 (scenario D) may improve the accuracy of detecting patients with “Severe ED” in the postoperative period of TURP. Clinical Trial Registration: NCT03936244 (https://clinicaltrials.gov/ct2/show/NCT03936244).