In Reply

Letters to the Editor regarding the article The Early Diagnosis and Treatment of Chronic Renal Insufficiency by Dr. med. Kai-Michael Hahn and Prof. Dr. med. Frank Strutz in issue 13/2024

We thank our correspondents for their important comments regarding the age-related physiological decline in eGFR of up to 1 mL/min/year from age 40, albeit with large variations between individuals. The problem of the KDIGO classification for chronic kidney disease by values of the glomerular filtration rate (GFR) is something that nephrologists such as ourselves have long been aware of and may indeed lead to excess diagnoses of renal insufficiency (1). An age-adapted CKD definition is therefore desirable and has actually been suggested numerous times. Age dependent thresholds for an eGFR of 75 mL/min for persons younger than 40, 60 mL/min for 40–64 year olds, and 45 mL/min for persons aged 65 and older have been applied (2). An agreement and implementation of an age-adjusted definition of renal insufficiency in the KDIGO heatmap is important but still requires a final consensus. The topic was extensively discussed in the KDIGO consensus conference, but the current decision was made against an age adjustment. So until further notice it is still up to nephrologists to point out to general practitioners the shortcomings of the international classification, to educate GPs about the age-related physiological decline of GFR, and to comment on the eGFR in patients’ medical reports (for example, in a 90 year old patient: eGFR 32 mL/min would be formally categorized as CKD 3b but corresponds to an age-adapted normal renal function, so that this patient should not be referred to a nephrologist—at least if the patient is not albuminuric). To enable a diagnosis of kidney disease in general practice, however, in addition to an eGFR according to CKD-EPI <60 mL/min persisting for more than three months, the urine-albumin-creatinine ratio (UACR) or dysmorphic erythrocyturia should be determined as criteria for renal injury—which is what we wanted to point out in our article (3).

DOI: 10.3238/arztebl.m2024.0162

Dr. med. Kai-Michael Hahn

Nephrologische Praxis, Dortmund

Prof. Dr. med. Frank Strutz

Nierenzentrum Wiesbaden Rheumatologie, DKD Helios Klinik Wiesbaden

Conflict of interest statement

K-MH received lecture fees from Astra Zeneca, Boehringer Ingelheim, and Bayer.

References

1. Liu P, Quinn RR, Lam NN, et al.: Accounting for age in the definition of chronic kidney disease. JAMA Intern Med 2021; 181: 1359–66

2. Delanaye P, Jager KJ, Bökenkamp A, et al.: CKD: a call for an age—adapted definition. J Am Soc Nephrol 2019; 30: 1785–1805

3. Hahn KM, Strutz F: The early diagnosis and treatment of chronic renal insufficiency. Dtsch Arztebl Int 2024; 121: 428–35