The quality of nifedipine studies used to assess tocolytic efficacy: a systematic review.
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.
Lamont
Ronnie F
RF
Department of Obstetrics and Gynaecology, Northwick Park Hospital and Imperial College, London, UK. pauline.mills@nwlh.nhs.uk
Khan
Khalid S
KS
Beattie
Bryan
B
Cabero Roura
Luis
L
Di Renzo
Gian Carlo
GC
Dudenhausen
Joachim W
JW
Helmer
Hanns
H
Svare
Jens
J
van Geijn
Herman P
HP
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*
D015149:Tocolytic Agents; D009543:Nifedipine