Predictive Correlation Between the International Index of Erectile Function (IIEF) and Sexual Health Inventory for Men (SHIM): Implications for Calculating a Derived SHIM for Clinical Use

Abstract

Validated questionnaires are used to assess postoperative continence, sexual function, and other quality-of-life issues after radical prostatectomy. The International Index of Erectile Function (IIEF) is one such well-tested inventory that is routinely used. However, some centers use the Sexual Health Inventory for Men (SHIM) or the IIEF-6 to record erectile function, and comparison between the three can be difficult. To define if there was a predictive correlation between IIEF (or IIEF-6) and SHIM, and to explore a strategy for the use of an abbreviated and rapid functional assessment of erectile function in patients. Preoperative and postoperative IIEF questionnaires from the robotic prostatectomy program at our institution were included in the study. The total IIEF, IIEF-6, and SHIM scores were calculated and correlations between the three were sought. We also looked at the feasibility of using only two questions from the IIEF with an aim of calculating both the SHIM and IIEF scores. The power to differentiate between patients with SHIM >or=22 from those with SHIM <or=21 for (i) the ratio allowing direct conversion of IIEF (or IIEF-6) to SHIM; and (ii) a two-question-based recalculation of SHIM. Two hundred seventy-five questionnaires were available for review. If the total IIEF score is known, the IIEF-derived SHIM score can be calculated by dividing the total IIEF score by a factor of 2.8 and then rounding off to a whole number. Furthermore, we have shown that an abbreviated questionnaire using Q5 and Q15 of the IIEF can be used to calculate the SHIM scores (two-question-SHIM). We described an easy way to calculate the SHIM score when the IIEF (or IIEF-6) score alone is known. The two-question model can be used for a rapid assessment of the patients' sexual function.