New comprehensive reference values for kidney function indexes across adult and geriatric ages in Chinese popuplation

China has the largest number of chronic kidney disease (CKD) patients. Current CKD definition has been challenged recently. We aim to reassess kidney function in healthy Chinese population, to provide a more appropriate reference range (RIs) for diagnosis, treatment, monitoring (or screening) of kidney disease and related research.

A total of 49627 apparently healthy people aged 18-94 years old were enrolled. Age and sex effects were explored for the kidney function indicators and RIs were calculated non-parametrically.

Albumin's limits were lower than the national RIs, with 5.7 g/L lower in upper limit (UL) and 0.4 g/L lower in lower limit (LL) [RIs: 39.6-49.3 vs 40-55]. The LL of estimate glomerular filtration rate (eGFR) was 80.4 mL/min/1.73 m² or 63.3 mL/min/1.73 m² at the age of <50 or ≥70 years, respectively. Notably, eGFR showed an approximately 0.7 mL/min/1.73 m² decrease every year. In addition, eGFR increase 0.35 mL/min/1.73 m² per standard deviation increase in blood glucose when uric acid (UA) exceed the RIs.

UA was an important factor affecting eGFR. For healthy elderly in China, albumin's limits were lower than the national RIs, and LLs of eGFR were nearly 60 mL/min/1.73 m². Using national RIs for healthy elderly may be overly stringent.