P-601 Deciding ‘THE most appropriate day’ of trigger for retrieving mature oocytes in IVF Cycles: Serum Plasminogen Activator Inhibitor-1, a robust prognostic bio-arbitrator decodes this dilemma

Abstract Study question Identification of a biomarker that holistically predicts follicle development and maturity, to decide apt trigger-day for retrieving optimal number of mature oocytes after IVF stimulation Summary answer Serum Plasminogen Activator Inhibitor-1 (PAI-1) level robustly dictates the appropriate trigger-day, predicting retrieval of optimal number of mature oocytes and enhanced implantation in IVF cycles What is known already Follicular cohort/size, Stimulation protocol/duration, ovarian-response status are the factors employed to decide trigger-day for inducing final oocyte maturation in IVF cycles. Conventionally, leading follicles size ≥18 mm, secondary/tertiary cohort follicle size ≥14 mm, 10-12 days of stimulation, levels of Estradiol, Progesterone, Luteinizing-hormone before trigger are associated with oocyte maturation. However, none of these factors solely or in conjunction, guarantee mature oocytes retrieval. PAI-1 is known to stringently regulate proteolysis during ovulation and implantation. We contended, low serum PAI-1 level corresponding to higher proteolytic activity during periovulatory phase of ovum-pickup may be an appropriate, superior biomarker of follicle and oocyte maturity Study design, size, duration Prospective cohort study in women aged 25-42 years (n = 211) undergoing IVF using antagonist stimulation protocol from August 2022 to October 2024. Serum PAI-1 levels on day of hCG and/or agonist trigger were prospectively measured by ELISA using diagnostic kits and retrospectively analysed using Graphpad prism-6 software. Serum levels of estradiol-E2, progesterone-P, Luteinizing-hormone LH were also measured on trigger-day (d-Trig). Statistical analysis involved Student’s-t test, Chi-square test, Correlation Coefficient, One-Way ANOVA, ROC analysis, as applicable. Participants/materials, setting, methods Cycles were divided initially in 2 but later in 3 groups as per serum PAI-1 levels on d-Trig as Low (<210 ng/ml, n = 59, <25th percentile), Medium (210-245 ng/ml, n = 70, 25th-50th percentile), High (>245 ng/ml,n=82, >50th percentile). Primary outcome measures: number of oocytes retrieved, %MII oocytes, %fertilization, %blastocyst formation. Secondary outcome measure: implantation rate. Embryo transfer cycles (n = 168): Transfer of 1 or 2 fresh/frozen embryos either on day3 cleavage or day5 blastocyst stage. Donor cycles were excluded Power of study >85% Main results and the role of chance Overall Mean Eggs retrieved=9.76, % MII oocytes=74.1%, Fertilization=79.83%, Blastocyst formation=43.71%. Implantation rate: Number of gestational sacs/number of embryos transferredx100 (76/254x100)=29.92% Low, Medium, High d-Trig/Sr.PAI-1 groups were similar w.r.t age (32.71 vs. 32.41 vs. 33.29 years, p=ns) and Mean eggs retrieved (9.57 vs. 8.1 vs. 11.14, p = 0.06) whereas showed significant statistical differences in % MII oocytes (63.74% vs. 97.28% vs. 65.43%, p < 0.0001), %Fertilization (55.42% vs. 92.11% vs. 59.13%, p = 0.008), %Blastocyst Formation (29% vs.68% vs. 36), %Implantation (19/80=23.75% vs. 30/70=42.86% vs. 27/104=25.96%) respectively. d-Trig Sr.PAI-1 levels (rather than Sr.E2 or Sr.P levels) correlated strongly with number of MII oocytes (Pearson r = 0.71,p<0.0001, 95%CI 0.66-0.74). The highest likelihood of retrieving mature oocytes was in the range of 185-240 ng/ml. ROCAUC=88%, p < 0.0001, Sensitivity=86%, Specificity=83% We had initially classified cycles into low (≤245ng/ml, n = 129) and high (>245ng/ml, n = 82) groups as per 50thcentile. Results corroborated with our contention that increased proteolytic/reduced inhibitor activity in periovulatory phase (coinciding with trigger-day), is indicative of higher follicle/oocyte maturity, irrespective of type/dose of trigger. Notably however, within the low-group; cycles with very low PAI-1 levels (<200 ng/ml) had lower %MII oocytes and developmental competency compared to those with PAI-1 levels 200-245 ng/ml. These findings suggest that optimal proteolytic regulation by PAI-1 bio-arbitrates oocyte maturity status. Limitations, reasons for caution Although serum PAI-1 is a robustly predictive biomarker of oocyte maturity status and implantation potential, the cost of measurement may be a deterrent. Therefore, it would be worthwhile to do multicentric studies and establish superiority of PAI-1 evaluation as standard practice, so that diagnostic kits become cheaper for routine use. Wider implications of the findings It was sheer serendipity that cycles with very low Sr.PAI-1 levels were those where stimulation duration had exceeded 12 days and/or mostly had post-mature oocytes, probably indicating ‘over-proteolysis’. It may be beneficial to measure Sr.PAI-1 level in advance anticipation, and accordingly either prepone or defer trigger-day for optimal mature-oocyte retrieval. Trial registration number No