title: Interpretation of the BBT chart: using the "Gap" technique compared to the Coverline technique.
abstract: OBJECTIVE
  The aim of the study was to compare the accuracy of the Gap and Coverline techniques of interpreting the basal body temperature chart.
  
  
  METHODS
  We compared the proportion of menstrual cycles for which the Gap and Coverline techniques accurately identified the post-ovulatory final fertile phase (FFP) and the initial infertile phase (IIP) and the median number of days each overestimated the fertile period, using urinary LH testing as the gold standard.
  
  
  RESULTS
  The Gap and Coverline techniques identified the FFP within +/-1 day of that identified by LH testing in 13/33 (39%) and 10/33 (30%) cycles (chi2=0.6; p=.44), respectively, and the IIP within +1 day of that of LH testing in 13/33 (55%) and 4/33 (12%) cycles, respectively (chi2=13.4; p<.001). The Gap and Coverline techniques overestimated the fertile period by 1 and 4 days, respectively (p=.0002).
  
  
  CONCLUSIONS
  Based on this small study, the Gap technique appears to be more accurate than the Coverline technique in identifying the post-ovulatory IIP.
authors.affiliation: Department of Family and Preventive Medicine, Emory University School of Medicine, Atlanta, GA 30303, USA. amlang@emory.edu
authors.forename: Anne
authors.initials: A
authors.lastname: Lang Dunlop
authors.forename: Robin
authors.initials: R
authors.lastname: Schultz
authors.forename: Erica
authors.initials: E
authors.lastname: Frank
mesh_terms: D000328:Adult; D001831:Body Temperature / Q000502:physiology*; D005260:Female; D005498:Follicular Phase; D006801:Humans; D008183:Luteal Phase; D007986:Luteinizing Hormone / Q000652:urine; D008597:Menstrual Cycle / Q000502:physiology*; D010061:Ovulation Detection / Q000379:methods; D044384:Ovulation Prediction / Q000379:methods; D015203:Reproducibility of Results
chemical_list: D007986:Luteinizing Hormone