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Literature and Evidence

The literature supporting the decision points and directives in this guideline is referenced throughout the document. The working group leaders were solicited for input on focal issues prior to a review of the literature.

A search was carried out using the National Library of Medicine’s (NLM) MEDLINE database. The term “kidney failure” was searched along with the following terms:

Epidemiology
Screening
Diagnosis
Primary Care
Protocols
Therapy
Patient Education
Economics

Forty articles were identified for inclusion in a table of information that was provided to each expert participant. The table of information contained:

Title
Author(s)
Author(s) affiliation
Publication type
Abstract
Source
Relevance

Copies of these tables were made available to all participants. Copies of specific articles were provided on an as needed basis.

The working group reviewed articles for relevance and graded the evidence using the following rating scheme, published by the U.S. Preventive Services Task Force (U.S. PSTF, 1996).

The U.S. Preventive Services rating scheme:

Strength of Recommendation (SR)

A

There is good evidence to support the recommendation that the condition be specifically considered in a periodic health examination.

B

There is fair evidence to support the recommendation that the condition be specifically considered in a periodic health examination.

C

There is insufficient evidence to recommend for or against the inclusion of the condition in a periodic health exam, but recommendations may be made on other grounds.

D

There is fair evidence to support the recommendation that the condition be excluded from consideration in a periodic health examination.

E

There is good evidence to support the recommendation that the condition be excluded from consideration in a periodic health examination.

  Quality of Evidence (QE)

I

Evidence obtained from at least one properly randomized controlled trial.

II-1

Evidence obtained from well-designed controlled trials without randomization.

II-2

Evidence obtained from well-designed cohort or case-control analytical studies, preferably from more than one center or research group.

II-3

Evidence obtained from multiple time series with or without the intervention. Dramatic results in uncontrolled experiments (such as the results of the introduction of penicillin treatment in the 1940s) could also be regarded as this type of evidence.

III

Opinions of respected authorities, based on clinical experience; descriptive studies and case reports; or reports of expert committees.

 


The QE rating is based on the quality, consistency, reproducibility, and relevance of the studies. Information about harmful effects must also be presented. The SR rating is influenced primarily by the science. Other factors that are taken into consideration when making an SR determination are:

The burden of suffering
Cost issues
Policy concerns.

For many recommendations, there is insufficient evidence to determine whether or not routine intervention will improve clinical outcomes. Lack of evidence of effectiveness does not mean there is evidence of ineffectiveness. Rather, lack of evidence (SR = C) means:

Insufficient statistical power or
Unrepresentative populations or
Lack of clinically important endpoints or
Design flaws (USPSTF, 1996).

The experts themselves, after an orientation and tutorial on the evidence grading process, formulated QE and SR ratings. Each reference was appraised for scientific merit, clinical relevance, and applicability to the populations served by the Federal health care system. Recommendations were based on consensus of expert opinions and clinical experience only when scientific evidence was unavailable.

The assembled experts were an invaluable source of additional information and suggested numerous references. These were distributed to participants on an as needed basis. It must be noted that this document does not, however, include reference to any publications dated after December, 1999. More recent information will be included in future guideline updates.