KorrTra – a correlational study on basal body temperature

The development of medical apps for fertility monitoring has increased in recent years. Mobile applications for family planning should be used based on evidence. This study examines the correlation of nightly intravaginal basal temperature measurement using the "trackle" sensor (medical device class IIb) as an alternative to the conventional morning measurement according to the symptothermal method "Sensiplan" (gold standard, symptothermal rules: double-check temperature with cervical mucus) [1]. METHODS/PROCEDURE KorrTra is a prospective monocentric study. Experienced "Sensiplan" users (n=51), aged 18-40 years years with a median age of 28, without hormonal contraception, pregnancy, or amenorrhea, were recruited. Both methods were applied in parallel for 2-6 months. The following variables were compared: the first higher measurement, the end of the temperature evaluation, and the last fertile day (LFRT, acc. to symptothermal rules: double-check temperature with cervical mucus). The temperature evaluation in both methods was carried out in accordance with the "Sensiplan"-method. Additionally, a case-by-case analysis was conducted when necessary. The ethics committee of the University of Heidelberg approved the procedure.

Since the date collection is still ongoing, perliminary data (302 cycles from 43 women) collected up to 12/07/24 was analyzed. The LFRT coincided in sixty-six percent (66%) of cycles in both methodes ("Sensiplan" and "trackle"), whereas there was an 88% correlation within +/- one day and 96% correlation within +/- two days. In total 25% of trackle cyles showed an earlier LFTR. The Pearson correlation coefficient for the LFTR was between 0.9 and 1. [Figure: scatter plot of LFRT differences by index; example cycle monitored with "Sensiplan" (grey) and "trackle" (blue).] DISCUSSION/CONCLUSION 1. The findings contribute to the evolving landscape of fertility monitoring by evaluating the efficacy of nocturnal intravaginal temperature measurement. 2. The preliminary data suggest a strong correlation between both methods. Although the deviation in the LFRT determined by both methods seems to be small, it could be still relevant for individuals relying on precise dermination of the fertile phase for family planning. 3. Twenty-five percent of the cycles recorded with the intravaginal sensor showed an earlier end of the fertile phase. This could indicate that the post-ovulatory phase might be recognized earlier, which may enhance the precision of fertility tracking, but in some cases also potentially entail a certain risk regarding efficacy of family planning. 4. The case-by-case analysis, which is presently underway, aims to identify areas of strengths as well as vulnerability inherent in the trackle-system.