King's Health Questionnaire to assess subjective outcomes after surgical treatment for urinary incontinence: can it be useful?

INTRODUCTION AND HYPOTHESIS: Midurethral slings (MUS) are the mainstay of treatment for stress urinary incontinence, but the definition of success varies widely amongst studies. The King's Health Questionnaire (KHQ) was designed to evaluate the impact of urinary incontinence on the quality of life. We hypothesised that the KHQ could be useful for postoperative quantitative assessment of subjective outcomes.
MATERIALS AND METHODS: This is a retrospective analysis of 204 patients who underwent incontinence surgery with transobturator MUS between 2004 and 2013. Follow-up was planned at 6, 12 and 24 months and success was evaluated using the cough stress test (objective cure) and the KHQ global score (subjective outcomes). Statistical analysis included receiver operating characteristic (ROC) curves to calculate a cut-off value for the KHQ global score to define subjective cure. The minimal clinically important difference was calculated with a distribution-based method (effect size) to estimate subjective improvement.
RESULTS: Objective cure rates were 97 % and 95 % at 6 and 24 months respectively. ROC curves established the cut-off score at ≤ 31 for subjective cure, with sensitivity of 63-100 % and specificity of 82-88 %. Subjective cure rates were 80 % and 85 % at 6 and 24 months respectively. The minimal clinically important difference was set at 10 and an improvement of ≥ 10 points was defined as subjective improvement. Rates varied between 10 and 13 %.
CONCLUSIONS: This study showed the value of the KHQ as an evaluation tool after UI surgery and determined clinically relevant threshold scores to define subjective outcomes.