What today's number supports, and what it does not

What is supported: today's paired estimates are 57.17 mL/min/1.73 m^2 (G3a) by creatinine and 60.40 mL/min/1.73 m^2 (G2) by the combined equation. They cross a category boundary and support a review of analytical identity, steady state, non-GFR influences, and the stated decision context; neither is measured GFR.

What is not supported: neither eGFR is a directly measured GFR, and a single result, however concordant, does not by itself establish a CKD diagnosis. KDIGO requires either another marker of kidney damage, such as albuminuria, or a persistently reduced eGFR generally sustained past 3 months. An eGFR of 60 or higher alone does not rule CKD in or out either; category and diagnosis are related but not the same determination.

What depends on method and local policy: the exact creatinine method (Jaffe or enzymatic), analyzer, reagent lot, and calibrator; the cystatin C method in local use (the Roche CYSC2 assay used in the guided case above is a representative, cited example, not a universal standard); the laboratory's own verified reference interval for each analyte, established under 42 CFR 493.1253 for its own patient population; whether the LIS auto-calculates eGFRcr, eGFRcr-cys, or both, and how it handles missing or invalid inputs; report comment wording and rounding rules; and any local calibration-verification schedule. None of those specifics is asserted here as a fixed fact; each is a local-policy card to be filled in at the laboratory that runs the assay.

An eGFR report should state the equation used, the units (mL/min/1.73 m^2), that the estimate is race-free, and a caution that the estimate may be less reliable during rapidly changing kidney function or unusual creatinine or cystatin C generation. Read every eGFR as a category-level estimate built on stated assumptions, confirm those assumptions hold for the patient in front of you, and reach for a second marker or a measured GFR exactly when the decision is big enough that being wrong would matter.