Electronic letters to:

Commentary:
Holger J. Schünemann, Dana Best, Gunn Vist, Andrew D. Oxman, and for The GRADE Working Group
Letters, numbers, symbols and words: how to communicate grades of evidence and recommendations
CMAJ 2003; 169: 677-680 [Abstract] [Full text] [PDF]
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Electronic letters published:

[Read eLetter] Grading the evidence!
Malvinder S. Parmar   (6 November 2003)
[Read eLetter] Re: Prior study of interest
Holger Schuenemann   (7 October 2003)
[Read eLetter] Prior study of interest
Adam L Scheffler   (1 October 2003)

Grading the evidence! 6 November 2003
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Malvinder S. Parmar
Timmins & District Hospital, Timmins, Ontario, Canada

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Re: Grading the evidence!

atbeat{at}ntl.sympatico.ca Malvinder S. Parmar

I read with great interest the essay by schunemann et al1] about grading of evidence. I agree with the authors that there is significant heterogeneity among different ‘interest groups’ and a uniform system of grading the rapidly generated evidence is required to effectively utilize this information in clinical practice. However, I believe that it is important first to properly assess the evidence if it is admissible or not, as done in the Court of law, before accepting and grading it. Evidence may be solid but if it is obtained without proper method(s) then it is not admissible in the Court of law and the same rule should apply in clinical medicine, where there is significant influence by the industry in the past few decades and evidence is often being created.

A randomized control trial (RCT) often provides the most reliable information, however, RCTs are influenced by a number of factors that introduce bias during the conduct, analysis, and reporting of the trial[2]. Specifically in current times, when most of the RCTs are conducted with the support and often are under the influence of the industry. For example, recently angiotensin receptor blockers (ARBs) were shown to retard proteinuria and progression of kidney disease in type 2 diabetes in RENAAL[3] and PRIME[4-5] trials. Although angiotensin converting enzyme inhibitors (ACE-I) were effective in slowing progression of renal disease in patients with[6] and without diabetes but these agents were specifically excluded from these trials. Since the publication of these trials, ARBs are being promoted to prevent progression of renal disease in type 2 diabetes and the American Diabetes Association[7] changed their guidelines in 2002 and advocate use of ARBs as first line agent, based on this evidence that is graded as Level 1 evidence, even though the evidence was clearly created. Is this really Level 1 evidence? These ARB trials in type 2 diabetic renal disease do not fulfill the criteria for “pure evidence-based medicine” and represent a bias in the design of the trials and makes a case for “Evidence-Made Medicine.”

Finally, I believe that before ranking the level of evidence one must review the conduct of trials and should first decide if the evidence is admissible or not. Where there is clear evidence that the so called ‘evidence’ is being created then these trials should be excluded from guidelines or recommendations, so that similar studies where evidence is being created to support an agent by the industry are not designed in future.

References:

1. Schunemann HJ, Best D, Vist G, Oxman AD for the GRADE working group. Letters, numbers, symbols and words: how to communicate grades of evidence and recommendations. CMAJ 2003; 169(7):677-679. 2. Stewart LA, Parmar MK. Bias in the analysis and reporting of randomized controlled trials. Int J Technol Assess Health Care 1996; 12(2):264-75. 3. Brenner BM, Cooper ME, Zeewu DD et al. Effects of Losartan on renal and cardiovascular outcomes in patients with type 2 diabetes and nephropathy. N Engl J Med 2001;345:861-9. 4. Lewis EJ, Hunsicker LG, Clarke WR et al. Renoprotective effect of the angiotensin-receptor antagonist Irbesartan in patients with nephropathy due to type 2 diabetes. N Engl J Med 2001;345:851-60. 5. Parving H-H, Lehnert H, Brochner-Mortensen J et al. The effect of Irbesartan on the development of diabetic nephropathy in patients with type 2 diabetes. N Engl J Med 2001;345:870-8. 6. Lewis EJ, Hunisicker LG, Bain RP, Rhode RD. The effect of angiotensin- converting-enzyme inhibition on diabetic nephropathy. N Engl J Med 1993;329:1456-62. 7. American Diabetic Association: Position Statement: Diabetic nephropathy. Diabetes Care 2002;25(Supplement1)S85-89.

Conflict of Interest:

None declared
Re: Prior study of interest 7 October 2003
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Holger Schuenemann
University at Buffalo

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Re: Re: Prior study of interest

hjs{at}buffalo.edu Holger Schuenemann

We thank Dr. Scheffler for his comment. We agree that the publication cited by Dr. Scheffler is related to the field and of interest to the reader, but it presents a review of selected available grading systems. The review does not deal with the issue of presentation of grading systems or offer a uniform approach. The latter is what the GRADE group has made its aim.

Holger Schünemann
Dana Best
Gunn Vist
Andy Oxman

Conflict of Interest:

None declared
Prior study of interest 1 October 2003
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Adam L Scheffler
Independent Journalist

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Re: Prior study of interest

adam_scheffler{at}yahoo.com Adam L Scheffler

CMAJ readers should note that in 2002 the US Agency for Healthcare Research and Quality (AHRQ) published a major study on related aspects of this topic. The citation follows.

Systems to Rate the Strength of Scientific Evidence. Evidence Report/Technology Assessment: Number 47. AHRQ Publication No. 02-E015, April 2002. Agency for Healthcare Research and Quality, Rockville, MD. Available at: http://www.ahrq.gov/clinic/tp/strengthtp.htm (accessed 29 September 2003).

Conflict of Interest:

None declared