CKD Staging (Cr vs. Cystatin C, Albuminuria & more): Mind The Gap Segment

Core IM

Welcome to Core IM’s CKD Staging (Cr vs. Cystatin C,  Albuminuria & more): Mind The Gap Segment

In this episode the team will discuss how to stage CKD using the dual-staging system recommended by KDIGO,  flaws of merely measuring renal function by eGFR, the significance of measuring albuminuria, and finally, the inequities involving minority patients who were commonly underdiagnosed and undertreated based on traditional CKD staging.

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Core IM

Welcome to Core IM, a virtual medical community! Core IM strives to empower its colleagues of all levels and backgrounds with clinically applicable information as well as inspire curiosity and critical thinking. Core IM promotes its mission through podcasts and other multimodal dialogues. ACP has teamed up with Core IM to offer continuing medical education, available exclusively to ACP members by completing the CME/MOC quiz.

Welcome to the “Stage”: GFR and Albuminuria

Reviewing CKD Classification!

  • Kidney Disease: Improving Global Outcomes (KDIGO) introduced a dual-staging criteria for chronic kidney disease (CKD)
    • eGFR Staging (G-Stage)
      • eGFR between 60 - 120 ml/min/1.73 m2
        • NOT clinically significant CKD
      • Stage G3
        • Stage G3a
          • 45 < eGFR < 59
        • Stage G3b
          • 30 < eGFR < 44
      • Stage G4
        • 15 < eGFR < 29
      • Stage G5
        • eGFR < 15
    • Albuminuria (A-Stage)
      • Measured by albumin-to-creatinine ratio (ACR) in mg/g
        • Stage A1
          • 0 < ACR < 30 mg/g
        • Stage A2
          • 30 < ACR < 300 mg/g
          • Moderately elevated (previously “microalbuminuria”)
        • Stage A3
          • > 300 mg/g  ACR
          • Severely elevated (previously “macroalbuminuria”)
  • Both the G-stage and A-stage are independent risk factors for cardiovascular and renal events! 

What’s WRONG with how we estimate GFR?

  • The ideal molecule to estimate GFR does NOT exist!
    • Ideal Qualities:
      • Exact serum quantity is known
      • Freely filtered at glomerulus
      • Neither secreted NOR reabsorbed in the tubules 
      • Ex: Insulin used historically
        • but cumbersome since requires injection
  • Why is creatinine flawed as an estimator of GFR? 
    • Creatinine is used as an endogenous estimator
    • Varies with muscle mass
      • Differs between patients based on:
        • Sex
        • Age 
      • Low muscle mass → lower levels of creatinine
        • Result: Cr will overestimate eGFR measurements & give false reassurance!
          • Example: Cr of 1 mg/dl in a 90-year-old frail female
      • Higher muscle mass → higher levels of creatinine
        • Result: Cr will underestimate eGFR measurements
          • Ex. Serum Cr of 1.8 mg/dL in Arnold Schwarzenegger or Shaq


Assessing Qualitative Renal Function using A-Stage! (Albuminuria)


Shreya Trivedi, MD, ACP Member – Editor
Gregory Katz, MD – Host, Editor
Cary Blum, MD – Host, Editor
Yichi Zhang, MD, MBA – Editor, MOC Questions


Tomas Guerrero, MD
Tejas Patel, MD

Those named above, unless otherwise indicated, have no relevant financial relationships to disclose with ineligible companies whose primary business is producing, marketing, selling, re-selling, or distributing healthcare products used by or on patients.  All relevant relationships have been mitigated.

Release Date:  November 8, 2023

Expiration Date: November 7, 2026

CME Credit

This activity has been planned and implemented in accordance with the accreditation requirements and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint providership of the American College of Physicians and Core IM.  The American College of Physicians is accredited by the ACCME to provide continuing medical education for physicians.

The American College of Physicians designates this enduring material (podcast) for .5 AMA PRA Category 1 Credit™.  Physicians should claim only the credit commensurate with the extent of their participation in the activity.

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Successful completion of this CME activity, which includes participation in the evaluation component, enables the participant to earn up to .5 medical knowledge MOC Point in the American Board of Internal Medicine’s (ABIM) Maintenance of Certification (MOC) program.  Participants will earn MOC points equivalent to the amount of CME credits claimed for the activity. It is the CME activity provider’s responsibility to submit participant completion information to ACCME for the purpose of granting ABIM MOC credit.

How to Claim CME Credit and MOC Points

After listening to the podcast, complete a brief multiple-choice question quiz. To claim CME credit and MOC points you must achieve a minimum passing score of 66%. You may take the quiz multiple times to achieve a passing score.