Levator ani defect scores and pelvic organ prolapse: is there a threshold effect?

INTRODUCTION AND HYPOTHESIS: The goal of this study was to use a well-described system of quantifying levator ani defect (LAD) severity using magnetic resonance imaging (MRI) to examine the relationship between defect severity and the presence or absence of prolapse.
METHODS: This is a secondary analysis of two case-control studies comparing 284 cases (with prolapse) to 219 controls (normal support) defined by using Pelvic Organ Prolapse Quantification (POP-Q) exams. LAD were assessed on MRI, with scores from 0 (no defects) to 6 (complete, bilateral defects). The number of cases and controls at each score were compared. Logistic regression and receiver operating characteristic (ROC) analyses were used to quantify relationships between LAD and prolapse.
RESULTS: The proportion of cases exceeds the overall prolapse rate in this study at LAD scores ≥3, with higher rates of prolapse at higher LAD scores (p < 0.0000001). Prolapse risk stratifies into low risk at LAD scores 0-2, moderate at 3-5, and high at 6. ROC analysis for classification of prolapse based on LAD scores has an area under the curve of 69.9% (p < 0.001), suggesting LAD alone can discriminate between normal support and prolapse for nearly 70% of patients. Logistic regression identified higher parity and higher LAD scores as independent predictors of prolapse.
CONCLUSIONS: There are three clusters of prolapse risk: low (0-2), moderate (3-5), and high (6). Although LAD have a dose-response-like effect for prolapse, other factors are clearly involved.