title: Association of study type, sample size, and follow-up length with type of recommendation produced by the National Institute for Health and Clinical Excellence Interventional Procedures Programme.
abstract: OBJECTIVE
  The association between type and amount of clinical evidence and type of National Institute for Health and Clinical Excellence recommendations for interventional procedures was examined.
  
  
  METHODS
  The evidence about 736 studies (including 183,729 patients) relating to 130 different interventional procedures and about relevant recommendations was analyzed. Associations were examined between type of recommendation ("normal arrangements" or "cautionary guidance") and evidence type, total number of treated patients, and mean follow-up length. Evidence type was categorized as (a) randomized, (b) nonrandomized controlled, and (c) case series/reports. The main outcome measures were frequency of evidence type, total number of patients treated, and mean follow-up length, by type of recommendation.
  
  
  RESULTS
  "Normal arrangements" recommendations were made for 70 (54 percent) procedures and "cautionary guidance" was issued for 60 (46 percent) procedures. Procedures supported by at least one randomized study (34 percent, n = 44) were more likely to receive a "normal arrangements" recommendation (relative risk 1.38, p = .063). Overall, there were 85 (12 percent), 135 (18 percent), and 516 (70 percent) studies in categories a-c, respectively. The number of treated patients was significantly larger among procedures with "normal arrangements" (median, 605; range, 26-6,842) than among those with "cautionary guidance" (median, 240; range, 1-3,261; p < .001) recommendation. Mean follow-up length was longer in studies relating to procedures with "normal arrangements" recommendation (median, 16.7; range, 0-84 months) compared with those with "cautionary guidance" (median, 14.6; range, 0-67 months; p = .160).
  
  
  CONCLUSIONS
  Procedures supported by randomized studies, and with larger numbers of patients and longer follow-up length, were more likely to receive positive guidance. Future research and development on interventional procedures should aim to produce better and more relevant evidence to optimize the possibility of such procedures being accepted by policy makers.
authors.affiliation: Royal Devon and Exeter Hospital and National Institute for Health and Clinical Excellence, 71 High Holborn, London, UK. bruce.campbell@nice.org.uk
authors.forename: William Bruce
authors.initials: WB
authors.lastname: Campbell
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Barnes
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Kirby
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Willett
authors.forename: Sally
authors.initials: S
authors.lastname: Wortley
authors.forename: Georgios
authors.initials: G
authors.lastname: Lyratzopoulos
mesh_terms: D006077:Government Agencies; D012107:Research Design; D013673:Technology Assessment, Biomedical / Q000379:methods*; D006113:United Kingdom