Using the ovarian sensitivity index to define poor, normal, and high response after controlled ovarian hyperstimulation in the long gonadotropin-releasing hormone-agonist protocol: suggestions for a new principle to solve an old problem

Objective To explore the utility of using the ratio between oocyte yield and total dose of FSH, i.e., the ovarian sensitivity index (OSI), to define ovarian response patterns. Design Retrospective cross-sectional study. Setting University-affiliated private center. Patient(s) The entire unselected cohort of 7,520 IVF/intracytoplasmic sperm injection treatments (oocyte pick-ups [OPUs]) during an 8-year period (long GnRH agonist–recombinant FSH protocol). Intervention(s) None. Main Outcome Measure(s) The distribution of the OSI (oocytes recovered × 1,000/total dose of FSH), the cutoff levels for poor and high response, set at ±1 SD, and the relationship between OSI and treatment outcome. Result(s) OSI showed a log-normal distribution with cutoff levels for poor and high response at 1.697/IU and 10.07/IU, respectively. A nomogram is presented. Live-birth rates per OPU were 10.5 ± 0.1%, 26.9 ± 0.6%, and 36.0 ± 1.4% for poor, normal, and high response treatments, respectively. The predictive power (C-statistic) for OSI to predict live birth was superior to that of oocyte yield. Conclusion(s) The OSI improves the definition of ovarian response patterns because it takes into account the degree of stimulation. The nomogram presents evidence-based cutoff levels for poor, normal, and high response and could be used for unifying study designs involving ovarian response patterns.