Author(s): Kwong YT, Stevens LA, Selvin E, Zhang YL, Greene T,
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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 30\%. Reducing and quantifying errors in gold-standard measurements of GFR is critical to fully estimating the accuracy of GFR estimates.
This article was published in Am J Kidney Dis and referenced in Journal of Medical Diagnostic Methods