title: The quality of nifedipine studies used to assess tocolytic efficacy: a systematic review.
abstract: OBJECTIVE
  To assess the quality of studies of nifedipine used to treat spontaneous preterm labor.
  
  
  METHODS
  A systematic review of study quality using a novel validity assessment tool, examining method-specific and topic-specific items in the domains of selection, performance and measurement biases.
  
  
  METHODS
  Medline (1996-2003), EMBASE (1996-2003), BIOSIS (1993-2003), Current Contents (1995-2003), DERWENT DRUGFILE (1983-2003), Cochrane Database of Systematic Reviews. Bibliographies of existing meta-analyses and systematic reviews of nifedipine as a tocolytic.
  
  
  METHODS
  Forty-five studies evaluating the effectiveness of nifedipine were identified.
  
  
  METHODS
  Each study was assessed for 40 method-specific and topic-specific items of quality in duplicate using piloted data extraction forms. Disagreements between assessors were settled by consensus/arbitration.
  
  
  RESULTS
  Very few of the studies complied with adequacy criteria of quality for either method-specific or topic-specific items. There was no improvement in quality over time. The quality of method-specific items was significantly poorer when compared with topic-specific items of quality overall (P<0.0001) and in the domains of selection bias (P<0.0001) and performance bias (P<0.0001).
  
  
  CONCLUSIONS
  Studies of the effectiveness of nifedipine as a tocolytic are of poorer quality with respect to method-specific items than topic-specific items. These deficiencies should be highlighted in meta-analyses or systematic reviews which measure efficacy and should influence the generation of guideline statements or recommendations for the use of nifedipine as a tocolytic. A large randomized trial fulfilling the quality items is necessary to assess the real efficacy of nifedipine in preterm labor.
authors.affiliation: Department of Obstetrics and Gynaecology, Northwick Park Hospital and Imperial College, London, UK. pauline.mills@nwlh.nhs.uk
authors.forename: Ronnie F
authors.initials: RF
authors.lastname: Lamont
authors.forename: Khalid S
authors.initials: KS
authors.lastname: Khan
authors.forename: Bryan
authors.initials: B
authors.lastname: Beattie
authors.forename: Luis
authors.initials: L
authors.lastname: Cabero Roura
authors.forename: Gian Carlo
authors.initials: GC
authors.lastname: Di Renzo
authors.forename: Joachim W
authors.initials: JW
authors.lastname: Dudenhausen
authors.forename: Hanns
authors.initials: H
authors.lastname: Helmer
authors.forename: Jens
authors.initials: J
authors.lastname: Svare
authors.forename: Herman P
authors.initials: HP
authors.lastname: van Geijn
mesh_terms: D005260:Female; D006801:Humans; D009543:Nifedipine / Q000627:therapeutic use*; D007752:Obstetric Labor, Premature / Q000517:prevention & control*; D011247:Pregnancy; D011642:Publications / Q000592:standards; D016032:Randomized Controlled Trials as Topic / Q000592:standards*; D015149:Tocolytic Agents / Q000627:therapeutic use*
chemical_list: D015149:Tocolytic Agents; D009543:Nifedipine