Purpose: To determine whether an optimal method exists for the detection of the luteinising hormone (LH) surge onset in research datasets of urinary hormonal profiles of menstrual cycles.
Methods: The scientific literature was searched to compare published methodologies for detection of the LH surge onset in urine. Their performance was tested using complete hormonal profiles from 254 ovulatory cycles from 227 women attempting pregnancy (normal regular menstrual cycles; no known infertility).
Results: Three major methodologies to determine the onset of the LH surge in urine were identified. The key difference between these methods is how the cycle days that contribute to LH baseline assessment are determined: using fixed days (method #1), based on peak LH day (method #2), based on a provisional estimate of the LH surge (method #3). Method #1 requires no prior cycle information, whereas methods #2 and #3 need to consider complete cycle data. The most reliable method for calculation of baseline LH was using 2 days before the estimated surge day, plus the previous 4/5 days.
Conclusions: Different methods for identification of the urinary LH surge can provide very different determinations of LH surge day, thus care must be taken when comparing between studies that apply different methodologies. The optimal method for determining the onset of the LH surge in urine requires retrospective estimation of day of LH surge to identify the most appropriate part of the cycle to consider as the baseline. This method can be adopted for application in population studies.
Keywords: LH; LH surge; Luteinising hormone; Menstrual cycle.