This observational study investigates whether a single set of GFR and urine albumin-to-creatinine ratio (ACR) thresholds can accurately screen for rapid kidney function decline in different elderly groups.

Inclusion Criteria:

1. Age greater than 70 years;
2. GFR data measured at least twice (two years apart) and ACR data measured once (at baseline);
3. A clear record of the cause of the previous visit; from this, people diagnosed with kidney disease were selected, and kidney disease was defined as various primary nephritis, secondary nephropathy, acute kidney injury (AKI), chronic kidney disease, kidney tumors, or a diagnosis of proteinuria alone.
4. Signed informed consent form.

Exclusion Criteria:

1. People with missing baseline biochemical data;
2. Outliers in the population indicators, i.e., data deviating from the mean ± three times the standard deviation;
3. Data with significantly abnormal baseline renal function follow-up (abnormally elevated GFR by more than 10% within 2 years or abnormal ACR value as determined by consultation with a senior nephrologist).

kidney disease patient