Overview
eGFR estimates GFR from filtration markers and demographic inputs using guideline-endorsed equations.
Clinical Importance
Stage and monitor chronic kidney disease (KDIGO)
Support drug dosing and nephrology referral thresholds
Specimen Requirements
Calculated from IDMS-traceable creatinine ± cystatin C and required demographics; not a separate wet chemistry reaction.
- Specimen: serum or lithium heparin plasma (method- and analyzer-dependent; follow the performing laboratory)
- Tube: gold/SST (serum separator) or green-top lithium heparin as validated locally
- Handling: invert gently; allow SST to clot fully before centrifugation; separate promptly
- Storage: refrigerate serum/plasma if testing is delayed per analyte stability limits
- Stability: analyte-specific; do not exceed institutional or manufacturer time/temperature limits
- Fasting: follow institutional/protocol fasting requirements when the ordered pathway requires fasting
Analytical Method
Mathematical estimate (CKD-EPI creatinine, cystatin C, or combined equations per laboratory/LIS configuration).
Instruments Used
Automated analyzers
- LIS/middleware calculators linked to chemistry analyzers reporting creatinine ± cystatin C
Manual methods
- Manual equation application (not preferred for reporting)
Reference Values
Typical adult SI examples below follow widely published international clinical chemistry practice (e.g., Tietz; Henry's). Always interpret against the method- and demographics-specific interval printed on the patient report (CLSI EP28-A3c). Neonatal, pediatric, pregnancy, and assay-generation intervals differ.
Reported in mL/min/1.73 m². Many adults are near ≥90 when kidney function is normal; KDIGO CKD staging uses eGFR categories; verify local equation and reporting rules.
Interpretation
Common Causes of Increased Results
- Higher eGFR indicates better estimated filtration; very high values may reflect low creatinine generation
Common Causes of Decreased Results
- Lower eGFR indicates reduced estimated filtration; confirm with clinical context and urine albumin
Clinical Significance
- CKD detection and staging with albuminuria
- Longitudinal kidney function monitoring
Factors Affecting Results
Pre-analytical
- Any creatinine/cystatin preanalytical error
Analytical
- Wrong equation version; non-traceable creatinine
Post-analytical
- Using race coefficients inconsistently with current local equation policy
Advantages and Limitations
Advantages
- Standardized reporting language for kidney function
Limitations
- Less accurate at extremes of muscle mass/age
- Not a substitute for measured GFR when precision is critical
Clinical Pearls
eGFR is only as good as the creatinine (or cystatin) method and the equation your laboratory actually uses.
References
Authoritative textbooks, guidelines, and reviews supporting this laboratory test reference. Verify reference intervals, critical limits, and method details against institutional protocols and current guideline editions.
Textbooks
- Rifai N, Horvath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 8th ed. Elsevier; 2022.
- McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Elsevier; 2021.
- Bishop ML, Fody EP, Schoeff LE. Clinical Chemistry: Principles, Techniques, and Correlations. 9th ed. Jones & Bartlett; 2022.
CLSI and Professional Guidelines
- International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). Recommendations and reference measurement systems for clinical chemistry measurands (verify current IFCC documents for the analyte).
- Clinical and Laboratory Standards Institute. Defining, Establishing, and Verifying Reference Intervals in the Clinical Laboratory; Approved Standard. CLSI document EP28-A3c. CLSI; 2010.
- Clinical and Laboratory Standards Institute. Collection of Diagnostic Venous Blood Specimens. CLSI standard GP41. CLSI.
- American Diabetes Association. Standards of Care in Diabetes. Diabetes Care (annual update).
- Kidney Disease: Improving Global Outcomes (KDIGO). Clinical Practice Guideline for Evaluation and Management of Chronic Kidney Disease.
- American Association for the Study of Liver Diseases (AASLD). Practice guidance related to evaluation of abnormal liver chemistries / liver disease laboratory evaluation (verify current AASLD publication and institutional adoption).
- Kidney Disease: Improving Global Outcomes (KDIGO). Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease (current edition).
Frequently Asked Questions
Common questions about using this eGFR laboratory test Medical Laboratory Library reference in Medical Laboratory Science education.
What is the eGFR laboratory test reference used for?
This Medical Laboratory Library page summarizes the clinical importance of eGFR. Review the Clinical Importance section for why the test is ordered in laboratory medicine practice.
Where can I find eGFR specimen requirements?
See the Specimen Requirements section on this page for specimen information related to eGFR. Confirm collection details against your laboratory protocol.
Where are eGFR reference values listed?
See the Reference Values section on this Laboratory Library page. Reference ranges can vary by method and population, so verify intervals with your laboratory.
How do I interpret eGFR results?
Use the Interpretation section for laboratory interpretation framing, including increased and decreased result patterns when provided. Do not treat educational text as a patient-specific diagnosis.
What analytical method is used for eGFR?
See the Analytical Method section for principle and method notes. Method details may differ by instrument and institutional SOP.
Are related laboratory tests linked from eGFR?
Yes. The Related Laboratory Tests section lists connected references for continued lookup in the Medical Laboratory Library.
How can I continue learning after reading eGFR?
Use Continue learning links on this page for related Academy lessons, medical laboratory quizzes, or laboratory case studies when available for this Clinical Chemistry topic.
What are the clinical pearls for eGFR?
See the Clinical Pearls section for concise laboratory practice notes associated with eGFR. Apply pearls alongside institutional protocols.
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