P-614 The use of home ovulation prediction kits (OPKs) in true natural cycle frozen embryo transfer (NC FET)
Authors: Rozon C , Corsi D , Meng L , Shmorgun D , Wu C , Gale J 
Published: July 2024

Study question

Do urinary OPKs have inferior ability to detect the LH surge compared to daily serum monitoring among patients undergoing true NC FET?

Summary answer

OPKs are highly accurate and may serve as reliable tests to detect the LH surge among patients undergoing NC FET.

What is known already

Frozen embryo transfers continue to increase worldwide and recent evidence suggests natural cycle protocols may be superior to hormone replacement protocols because of lower risk of miscarriage and lower risk of pregnancy complications. Patients undergoing NC FET attend multiple clinic appointments which has been associated with increased patient stress levels during fertility treatment. OPKs have been found to be accurate at detecting the LH surge in the trying to conceive population and have high user acceptability.

Study design, size, duration

A prospective single cohort study including 139 fertility seeking participants was completed at an academic-affiliated fertility center for a duration of 12 months.

Participants/materials, setting, methods

Patients scheduled for NC FET (regular cycles 27-35 days, mid luteal progesterone &gt;30 nmol/L, no luteal phase concern) with the ability to provide informed consent and access to SMS texting devices were eligible for participation. On the same day they started daily morning bloodwork as per the standard protocol (2-3 days prior to anticipated LH surge), participants began twice daily OPK testing. Upon exiting the study, patients completed a questionnaire on satisfaction with OPK use.

Main results and the role of chance

LH surge detection rate was 85.6% (n = 119/139) with serum monitoring and 93.5% (130/139) with OPK use (Kappa agreement 90.7%, K = 0.51, p &lt; 0.001). Among patients with a serum-detected LH surge, OPK was positive within +/- 12 hours of the serum LH surge detection in 84.8% of patients. In 23.7% of cycles, OPK was positive the same morning as serum blood work. In 27.1% of cycles, OPK was positive 12h prior and in 33.9% of cycles, OPK was positive 12h after serum LH surge detection. Actual NC FET cycle cancellation rate was 16.6% (n = 23/139) compared to an anticipated cycle cancellation rate of 20.9% (29/139) if OPKs had been used to initiate serum monitoring. The average reduction in the number of serum monitoring visits and distance travelled in kilometers with OPK use was 3.9 visits (SD 2.1) and 155km (SD 174), respectively. The majority of participants reported satisfaction with OPK use.

Of 135 patients, 110 (81.5%) strongly agreed the OPK was easy to use, 100 (74.1%) strongly agreed they would be open to using OPKs in future fertility treatments and 120 (88.9%) reported a reduction or no impact on stress levels associated with fertility treatments.

Limitations, reasons for caution

This study only used Clearblue Digital Ovulation Tests and the reported reliability in our study cannot be extrapolated to all OPKs. Additionally, the accuracy of the reported serum LH surge detection rate may be limited by physician specific definitions of serum LH surge.

Wider implications of the findings

OPKs are highly accurate and may serve as a reliable trigger for serum monitoring in NC FET. While their use would reduce the number of clinic appointments and distance travelled for patients undergoing NC FET cycles, patients should be advised OPK use may be associated with higher cycle cancellation rates.

Trial registration number

Not applicable