The Number, Quality, and Coverage of Randomized Controlled Trials in Nephrology

Giovanni F.M. Strippoli, Jonathan C. Craig, Francesco P Schena

Research output: Contribution to journalArticlepeer-review

270 Citations (Scopus)


ABSTRACT. Randomized controlled trials (RCT) are the optimal study design to answer intervention questions. The authors evaluated the number, quality, and coverage of RCT in nephrology. MEDLINE was searched using the relevant medical subject headings for nephrology and 12 major specialties in internal medicine, limited by “randomized controlled trial” as a publication type. A random selection of 160 RCT in nephrology (40 for each decade) published since 1966 and an additional 270 RCT from ongoing or published Cochrane systematic reviews in various areas of nephrology, dialysis, and transplantation were evaluated for quality of reporting using standard criteria. The number of RCT published in nephrology from 1966 to 2002 (2779) is fewer than all other specialties of internal medicine (range: 5335 in hematology to 27109 in cardiology) with the proportion of all citations which are RCT being the third lowest (1.15%). There has been an increase in both indices from 1966 to 1996, but not at a greater rate than other specialties, and there has been no increase over the past 5 yr. Some areas of nephrology, in particular glomerulonephritis, are clear outliers with very low numbers of RCT to guide clinical decision-making. Overall the quality of RCT reporting in nephrology is low and has not improved over the past 30 yr with unclear allocation concealment (89%), lack of reported blinding of outcome assessors (92%), and failure to perform “intention-to-treat analysis” (50%) particularly frequent. The challenges of improving the quality and quantity of trials in nephrology are substantial, but they can be overcome by using standard guidelines and checklists for trial reporting, greater attention to the trial methods and not just the results, involving experts in trial design and reporting, multicenter collaboration, and larger and simpler trials.

Because randomized controlled trials (RCT) are designed to provide unconfounded estimates of intervention effects, they are the ideal study type to answer intervention questions. However, not all RCT provide valid results. Validity of RCT depends on the underlying methodological quality (1). Allocation concealment, blinding, intention-to-treat analysis, and loss to follow-up are the critical items in the design and conduct of RCT, and inadequately conceived and conducted RCT, like observational studies, may overestimate or underestimate true effects of interventions.

To our knowledge, there has never been a systematic evaluation of the number, coverage, and quality of RCT in nephrology. This was the aim of our study. If problems were identified, we also sought to propose feasible solutions.
Original languageEnglish
Pages (from-to)411-419
Number of pages9
JournalJournal of The American Society of Nephrology
Issue number2
Publication statusPublished - Feb 2004
Externally publishedYes


  • nephrology
  • randomized controlled trial
  • literature search


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