Conclusions: High age- based uncorrected mGFR showed the most consistent associations reflective of hyperfiltration.

However, high age- based uncorrected mGFR has limited clinical utility because it does not distinguish between hyperfiltration and high nephron number.

A high age-height-gender- based uncorrected mGFR definition performed almost as well but had a weaker association with nephron number and did not associate with male gender.