title: Differences in reporting Pearl Indices in the United States and Europe: Focus on a 91-day extended-regimen combined oral contraceptive with low-dose ethinyl estradiol supplementation.
abstract: BACKGROUND
  Regulatory agencies in the United States (US) and Europe differ in requirements for defining pregnancies after the last dose of oral contraceptive, sometimes resulting in discrepant Pearl Indices (PIs) for the same product despite identical clinical data. This brief report highlights one such example, a 91-day extended-regimen combined oral contraceptive (COC).
  
  
  METHODS
  The US- and European-based PI methodologies were compared for a 91-day extended-regimen COC consisting of 84 days of active levonorgestrel/EE 150 μg/30 μg tablets, followed by seven days of EE 10 μg tablets in place of placebo.
  
  
  CONCLUSIONS
  At the times of approval of the 91-day extended-regimen COC in the US and Europe, the requirements for defining 'on-treatment' pregnancies differed (14-day vs. 2-day rule, respectively). This difference resulted in a higher PI in the US- vs. European-based calculation (1.34 and 0.76, respectively). The differences in the PI should not be interpreted as the extended-regimen COC being less effective in preventing pregnancy in the US compared with Europe.
authors.affiliation: a * Hospital Universitario Infanta Sofía, San Sebastián de los Reyes , Madrid , Spain.
authors.forename: Paloma
authors.initials: P
authors.lastname: Lobo Abascal
authors.affiliation: b CAIR Center - The House of Statistics , Zagreb , Croatia.
authors.forename: Vesna
authors.initials: V
authors.lastname: Luzar-Stiffler
authors.affiliation: c Medical Affairs EU, Pliva Croatia, Teva Group , Zagreb , Croatia.
authors.forename: Silvana
authors.initials: S
authors.lastname: Giljanovic
authors.affiliation: d Teva Global Medical Affairs , Frazer , PA , USA.
authors.forename: Brandon
authors.initials: B
authors.lastname: Howard
authors.affiliation: e Teva Global Medical Affairs , Petach Tikva , Israel.
authors.forename: Herman
authors.initials: H
authors.lastname: Weiss
authors.affiliation: f Office of Population Research, Princeton University , Princeton , NJ , USA.
authors.forename: James
authors.initials: J
authors.lastname: Trussell
mesh_terms: D003268:Contraception Behavior / Q000706:statistics & numerical data*; D003277:Contraceptives, Oral, Combined / Q000008:administration & dosage* / Q000009:adverse effects; D004334:Drug Administration Schedule; D004338:Drug Combinations; D004997:Ethinyl Estradiol / Q000008:administration & dosage* / Q000009:adverse effects; D005060:Europe; D005260:Female; D006801:Humans; D016912:Levonorgestrel / Q000008:administration & dosage* / Q000009:adverse effects; D017060:Patient Satisfaction; D011247:Pregnancy; D014481:United States; D016903:Drug Monitoring
chemical_list: D003277:Contraceptives, Oral, Combined; D004338:Drug Combinations; C072593:ethinyl estradiol, levonorgestrel drug combination; D004997:Ethinyl Estradiol; D016912:Levonorgestrel
keywords: Combined oral contraceptive; Extended-regimen; Pearl Index