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Questionable Validity of Creatinine-Based eGFR in Elderly Patients but Cystatin C Is Helpful in First-Line
Dario Geißer1, Lina Hetzel2, Ralf Westenfeld2
1Central Institute of Clinical Chemistry and Laboratory Diagnostics, Medical Faculty, Heinrich Heine University and University Hospital, 40225 Düsseldorf, Germany.
Insights
For elderly patients, creatinine-based estimated glomerular filtration rate (eGFR) may overestimate kidney function. Cystatin C-based eGFR (CAPA) offers a more accurate first-line diagnostic test for assessing chronic kidney disease (CKD) in this population.
Area of Science:
- Nephrology
- Clinical Chemistry
- Geriatric Medicine
Background:
- Current chronic kidney disease (CKD) diagnosis relies on creatinine-based estimated glomerular filtration rate (eGFR).
- Cystatin C-based eGFR may offer improved accuracy in assessing kidney function.
Purpose of the Study:
- To compare the diagnostic performance of creatinine-derived eGFR versus cystatin C-derived eGFR in elderly patients.
- To evaluate the impact of cystatin C-based eGFR on CKD classification in individuals over 60.
Main Methods:
- Retrospective analysis of 112 hospital patients aged over 60.
- Comparison of eGFR calculated using CKD-EPI (creatinine-based) and CAPA (cystatin C-based) formulas.
- Evaluation of accuracy against final case diagnoses for CKD.
Main Results:
- Cystatin C-based eGFR (CAPA) consistently yielded lower values than creatinine-based eGFR (CKD-EPI), averaging a 20% decrease.
- CKD reclassification occurred in 37% of cases, with 49% showing a lower CKD stage based on cystatin C.
- A significant portion of patients initially classified as 'no-CKD' were reclassified to kidney-insufficient states using CAPA.
Conclusions:
- Creatinine-based eGFR (CKD-EPI) systematically overestimates renal function in patients over 60.
- Cystatin C-based eGFR (CAPA) is recommended as the preferred first-line diagnostic test for this demographic.
- Utilizing cystatin C improves the accuracy of CKD diagnosis and staging in the elderly.
Background:
The recommended chronic kidney disease (CKD) first-line diagnostic test is based on the creatinine-derived (estimated) glomerular filtration rate (eGFR). Cystatin C use may provide a better assessment.
Methods:
We compared creatinine- and cystatin C-derived eGFR determination as the first-line diagnostic test for 112 hospital patients aged > 60 years (median = 76 years). The patients were judged to not have CKD (no-CKD group) according to the first-line diagnostic recommendations (n = 61, eGFR (CKD Epidemiology Collaboration (CKD-EPI)) ≥ 60 mL/min/1.73 m2, total urine protein < 150 mg/g creatinine, urinary red/white blood cells not increased) or classified to be at risk for kidney insufficiency due to aortic valve dysfunction (at-risk group; n = 51). The accuracy of the eGFR values was evaluated retrospectively with the final case diagnoses.
Results:
The eGFR (Caucasian, Asian, pediatric, and adult formula (CAPA)) was found to be linearly correlated to the eGFR (CKD-EPI) (R2 = 0.5, slope = 0.69, p < 0.0001). In 93/112 (>80%) cases, the eGFR (CAPA) yielded lower values (on average ≈-20%). In 55/112 (49%) cases, the cystatin C-derived CKD stage was lower. CKD reclassification from no-CKD to a kidney-insufficient state (i.e., CKD1/2 to CKD3a/b or 4) or reclassification to a more severe kidney insufficiency (i.e., CKD3a → 3b/4 or 3b → 4) was found in 41/112 (37%) cases. A worse CKD classification (no-CKD → kidney-insufficient) based on the eGFR (CAPA) was plausible in 30% of cases in light of the final case diagnoses.
Conclusion:
In elderly patients (>60 years), renal function appears to be systematically overestimated by the creatinine-based eGFR (CKD-EPI), indicating that, for this group, the cystatin C-based eGFR (CAPA) should be used as the first-line diagnostic test.
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