September 12, 2013

DynaMed EBM Journal Volume 8, Issue 37

DynaMed Weekly Updates

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Physicians: .25 AMA PRA Category ICreditsTM

Family Physicians: .25 Prescribed credits

Nurse Practitioners: .25 Contact hours

Release Date: September 4, 2013

Expiration Date: September 4, 2014

Estimated Completion Time: 15 minutes

There is no fee for this activity.

To Receive Credit

In order to receive your certificate of participation, you should read the information about this activity, including the disclosure statements, review the entire activity, take the post-test, and complete the evaluation form. You may then follow the directions to print your certificate of participation. To begin, click the CME icon at the end of the article.

Program Overview

Learning Objectives

Upon successful completion of this educational program, the reader should be able to:
1. Discuss the significance of this article as it relates to your clinical practice.
2. Be able to apply this knowledge to your patient's diagnosis, treatment and management.

Faculty Information

Alan Ehrlich, MD - Assistant Clinical Professor in Family Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA; Senior Deputy Editor, DynaMed, Ipswich, Massachusetts, USA

Michael Fleming, MD, FAAFP - Assistant Clinical Professor of Family Medicine and Comprehensive Care, LSU Health Science Center School of Medicine, Shreveport, Louisiana, USA; Assistant Clinical Professor of Family Medicine, Department of Family and Community Medicine, Tulane University Medical School, New Orleans, Louisiana, USA; Chief Medical Officer, Amedisys, Inc. & Antidote Education Company


Dr. Ehrlich, Dr. Fleming, DynaMed Editorial Team members, and the staff of Antidote Education Company have disclosed that they have no relevant financial relationships or conflicts of interest with commercial interests related directly or indirectly to this educational activity.

No commercial support has been received for this activity.

Accreditation Statements

ACCME: This activity has been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education through the joint sponsorship of Antidote EducationCompany and EBSCO Publishing. Antidote is accredited by the ACCME to provide continuing medical education for physicians. Antidote Education Company designates this enduring activity for a maximum of 0.25 AMA PRA Category 1 CreditsTM. Physicians should only claim credit commensurate with the extent of their participation in the activity.

AAFP: Enduring Material activity, DynaMed EBM Focus, has been reviewed and is acceptable for up to 13 Prescribed credits by the American Academy of Family Physicians. AAFP certification begins March 7, 2012. Term of approval is for one year from this date with the option of yearly renewal. Each EBM Focus is worth .25 Prescribed credits. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

AANP: This program is approved for 0.25 contact hour of continuing education by the American Academy of Nurse Practitioners.

Program ID: 1210393S


Last week 438 journal articles were evaluated via DynaMed's Systematic Literature Surveillance and summaries of 230 articles were added to DynaMed content.

Based on criteria for selecting "articles most likely to change clinical practice," one article of significant interest was selected by the DynaMed Editorial Team.

Estimation of Glomerular Filtration Rate Using Cystatin C Improves Risk Classification Compared to Estimation Using Creatinine
Reference: (N Engl J Med 2013 Sep 5;369(10):932), (level 1 [likely reliable] evidence)

Glomerular filtration rate (GFR) is a standard measure of kidney function that is used to stage chronic kidney disease (CKD). The KDIGO staging system defines CKD as GFR < 60 mL/minute/1.73 m2. CKD stages correspond to categories of GFR values, each with a range of 15 mL/minute/1.73 m2, with lower GFR values indicating higher stage (more severe) disease (KDIGO 2013 Jan PDF). Because direct measurement of GFR is difficult, it is usually estimated (eGFR) by an equation typically using age, sex, and biomarker parameters. Several different estimation methods (CKD-EPI, MDRD, Cockcroft-Gault) have used creatinine as the principle marker of renal function. Though data have been inconsistent across different patient populations, the CKD-EPI creatinine equation has been shown to be comparable to the commonly used MDRD equation (Scand J Clin Lab Invest 2011 Apr;71(2):129). Newer equations have recently been developed using cystatin C, either alone or in combination with creatinine, and they may be more accurate than creatinine-based equations. This is in part because the filtration rate of cystatin C is unaffected by age, race, gender or muscle mass. A recent large validation cohort study compared risk classification based on CKD-EPI equations using cystatin C or creatinine.

Individual data from 90,750 patients from 11 general-population cohorts who had had standardized baseline measurements of both serum creatinine and cystatin C were analyzed. eGFR was calculated for each patient using CKD-EPI equations using cystatin C or creatinine. At baseline, the prevalence of CKD was 13.7% using cystatin C equation and 9.7% using creatinine equation. All-cause mortality was 13.6% overall in mean follow-up of 7.7 years.

CKD staging using the cystatin C equation was compared to staging using the creatinine equation. Using cystatin C, 21.5% of patients were classified to a higher CKD stage, and 19.3% to a lower stage compared to their creatinine-based stage. Classification to a higher stage by the cystatin C equation was associated with significantly increased risk of mortality for each category of GFR values, with hazard ratios for risk of death ranging from 1.36 to 3.04 (p < 0.05 for each GFR category). Conversely, classification to a lower stage was generally associated with reduced risk or mortality, though these reductions were significant only for stages corresponding to GFR categories of 45-59 mL/minute/1.73 m2 and 30-44 mL/minute/1.73 m2.

The improvement in predictive performance using the CKD-EPI cystatin C equation was summarized by the net reclassification index (NRI), which assesses the relative rates of appropriate and inappropriate reclassification (with positive value indicating improvement). For all-cause mortality, the NRI was 23% (95% CI 18%-28%). The cystatin C equation also associated with improved performance for prediction of cardiovascular death (NRI 17%, 95% CI 11%-23%) and end-stage renal disease (NRI 10%, 95% CI 0%-21%). Performance of CKD-EPI equation using both cystatin C and creatinine was similar to that of the cystatin C only equation. Similar results were also obtained in additional analysis of 5 cohorts with 2,960 patients with chronic kidney disease at baseline.

For more information, see the Chronic kidney disease topic in DynaMed.

Earn CME Credit for reading this e-Newsletter.
For more information on this educational activity, see the CME sidebar.

DynaMed Events

American Academy of Family Physicians (AAFP) Conference, September 24-28, 2013
Senior Deputy Editor Alan Ehrlich, MD, will be attending the American Academy of Family Physicians conference, held at the San Diego Convention Center in San Diego, California. Representatives will be available to discuss peer review, mobile access, and free trial information.

Visit the American Academy of Family Physicians website to learn more about the event and for registration information.

ID Week, October 2-6, 2013
Deputy Editor Sheila Mitsuma, MD, will be attending ID Week, held at the Moscone Convention Center in San Fransisco, California. Representatives will be available to discuss peer review, mobile access, and free trial information.

Visit the ID Week website to learn more about the event and for registration information.

If you would like to meet with a DynaMed representative, please contact us at

Call for Peer Reviews

We are currently seeking reviewers for:

Acute epididymitis

Wilms tumor treatment protocols