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Imprecision of Urinary lothalamate Clearance as a Gold-Standard Measure of GFR Decreases the Diagnostic Accuracy of Kidney Function Estimating Equations.
- Source :
- American Journal of Kidney Diseases; Jul2010, Vol. 56 Issue 1, p39-49, 11p
- Publication Year :
- 2010
-
Abstract
- Background Evaluating the accuracy of estimated glomerular filtration rate (eGFR) derived from serum creatinine (SCr) and serum cystatin C (SCysC) equations requires gold-standard measures of GFR. However, the influence of imprecise measured GFRs (mGFRs) on estimates of equation error is unknown. Study Design Diagnostic test study. Setting & Participants 1,995 participants from the Modification of Diet in Renal Disease (MDRD) Study and African American Study of Kidney Disease and Hypertension (AASK) with at least 2 baseline mGFRs from iodine 125-iothalamate urinary clearances, 1 standardized SCr value, and 1 SCysC value. Index Tests eGFRs calculated using the 4-variable isotope-dilution mass spectrometry (IDMS)-traceable MDRD Study equation, the Chronic Kidney Disease (CKD) Epidemiology Collaboration (CKD-EPI) SCysC equation, the CKD-EPI SCr-SCysC equation, and mGFRs collected from another prerandomization visit. Reference Tests A single reference mGFR, average of 2, and average of 3 mGFRs; additional analysis limited to consistent mGFRs (difference ⩽25% from reference mGFR). Results We found that mGFRs had stable mean values, but substantial variability across visits. Of all mGFRs collected a mean of 62 days apart from the reference visit, 8.0% were outside 30% of the single reference mGFR (1 - P30). Estimation equations were less accurate because 12.1%, 17.1%, and 8.3% of eGFRs from the MDRD Study, CKD-EPI SCysC, and CKD-EPI SCr-SCysC equations were outside 30% of the same gold standard (1 - P30). However, improving the precision of the reference test from a single mGFR to the average of 3 consistent mGFRs decreased these error estimates (1 - P30) to 8.0%, 12.5%, and 3.9%, respectively. Limitations Study population limited to those with CKD. Conclusions Imprecision in gold-standard measures of GFR contribute to an appreciable proportion of the cases in which eGFR and mGFR differ by >30%. Reducing and quantifying errors in gold-standard measurements of GFR is critical to fully estimating the accuracy of GFR estimates. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 02726386
- Volume :
- 56
- Issue :
- 1
- Database :
- Supplemental Index
- Journal :
- American Journal of Kidney Diseases
- Publication Type :
- Academic Journal
- Accession number :
- 52419999
- Full Text :
- https://doi.org/10.1053/j.ajkd.2010.02.347