title: Accuracy of calendar-based methods for assigning menstrual cycle phase in women.
abstract: BACKGROUND
  Sex steroid hormone fluctuations during the menstrual cycle are considered a risk factor for noncontact anterior cruciate ligament injuries.
  
  
  OBJECTIVE
  To determine whether self-reported menstrual history data can be used to accurately categorize menstrual cycle events using calendar-based counting methods.
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  Seventy-three women completed a menstrual history questionnaire and submitted to blood sampling for the first 6 days of menses and 8 to 10 days after a positive ovulation test over 2 consecutive months. Frequency counts determined whether appropriate criterion hormone (progesterone) levels were achieved at predefined calendar days.
  
  
  RESULTS
  For the criterion of progesterone >2 ng/mL, 18% and 59% of women attained it when counting forward 10 to 14 days after the onset of menses and counting back 12 to 14 days from the end of the cycle, respectively. Most women (76%) attained the criterion for ovulation 1 to 3 days after a positive urinary ovulation test. Regardless of the counting method employed, the criterion of progesterone >4.5 ng/mL for identifying midluteal phase was attained in 67% of cases. Serial blood sampling for 3 to 5 days after the positive urinary ovulation test captured 68% to 81% of the hormone values indicative of ovulation and 58% to 75% indicative of the luteal phase.
  
  
  CONCLUSIONS
  These data suggest that self-reported menstrual history and calendar-based counting methods should not be used alone if accurate identification of ovulation is essential. A urinary ovulation test and serial blood samples for verification of progesterone postovulation enhance the proper identification of menstrual cycle events.
  
  
  CONCLUSIONS
  Given the cost of serial blood sampling on numerous days, the use of urinary ovulation kits and strategically selected serial blood sampling could significantly reduce participant burden and provide cost-effective measures for clinical studies related to anterior cruciate ligament injury epidemiology.
authors.affiliation: Department of Kinesiology, University of North Carolina Greensboro, Greensboro, North Carolina.
authors.forename: Laurie
authors.initials: L
authors.lastname: Wideman
authors.affiliation: Department of Kinesiology, University of North Carolina Greensboro, Greensboro, North Carolina.
authors.forename: Melissa M
authors.initials: MM
authors.lastname: Montgomery
authors.affiliation: Department of Public Health Education, University of North Carolina Greensboro, Greensboro, North Carolina.
authors.forename: Beverly J
authors.initials: BJ
authors.lastname: Levine
authors.affiliation: Department of Orthopedics and Rehabilitation, College of Medicine, University of Vermont, Burlington, Vermont.
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Beynnon
authors.affiliation: Department of Kinesiology, University of North Carolina Greensboro, Greensboro, North Carolina.
authors.forename: Sandra J
authors.initials: SJ
authors.lastname: Shultz
keywords: positive urinary ovulation test; progesterone; self-reported menstrual history