Kidney age - chronological age difference (KCD) score provides an age-adapted measure of kidney function

Has the time come for age-adapted glomerular filtration rate criteria to define chronic kidney disease: how soon is now?

PURPOSE OF REVIEW

The conventional definition of chronic kidney disease (CKD) primarily relies on the identification of albuminuria or a decline in estimated glomerular filtration rate (eGFR). For many years, a straightforward eGFR threshold of <60 ml/min/1.73 m 2 has been widely adopted as the standard for defining CKD. Nonetheless, this criterion fails to consider the natural aging process of the kidney, and this oversight may affect the accurate diagnosis of kidney disease particularly at the extremes of age.

RECENT FINDINGS

The fixed eGFR threshold of <60 ml/min/1.73 m 2 for defining CKD misses crucial opportunities for risk prevention. Studies have revealed that the eGFR threshold at which the risks for adverse long-term health outcomes such as mortality, cardiovascular events, and kidney failure begin to rise varies substantially by age. Specifically, this threshold is lower for the elderly and higher for young adults. Consequently, this results in the over-diagnosis of kidney disease in the elderly and the under-diagnosis of kidney disease in young adults.

SUMMARY

To address these limitations of the current CKD definition, we discuss a number of proposed age-adapted eGFR criteria and weigh their pros and cons against the current, simple, and universally accepted approach.

Prediction of cardiovascular death and non-fatal cardiovascular events by the Kidney age-Chronological age Difference (KCD) score in men and women of different ages in a community-based cohort

OBJECTIVE

We examined the utility of the Kidney age-Chronological age Difference (KCD) score, an age-adapted measure of kidney function, to identify increased cardiovascular (CV) death or non-fatal CV event risk in participants of the Australian Diabetes, Obesity, and Lifestyle Study (AusDiab), a community-based cohort aged 23-95 years.

DESIGN

Cohort study.

SETTING

Community.

PARTICIPANTS

11205 randomly selected participants from urban and nonurban areas across Australia.

OUTCOME MEASURES

Mortality status and underlying and contributory causes of death obtained from the Australian National Death Index, and non-fatal CV events from adjudicated hospital records. The association of CV death or non-fatal CV event risk with KCD score was examined using penalised spline curve analysis.

RESULTS

Of 11 180 participants with serum creatinine measurement at baseline and 5-year outcome data, there were 308 CV deaths or non-fatal CV events after 5 years. Penalised spline curve analysis showed similar progressive increase in CV death or non-fatal CV event risk with increasing KCD score in men and women, and participants aged <50 years to ≥80 years. Receiver operating characteristic curve analysis showed optimal discrimination at a KCD score ≥20 years (KCD20) for all participants. Among 148 participants aged<70 years with CV death or non-fatal CV event, KCD20 identified 24 (16%) participants, whereas estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m² identified 8 (5%) participants (p=0.0001), with specificities of 95% and 99%, respectively (p<0.0001).

CONCLUSION

KCD20 predicted CV death or non-fatal CV event risk similarly in men and women of different ages in this population-based cohort. The higher sensitivity for prediction of CV death or non-fatal CV event risk in participants aged <70 years by KCD20 than by eGFR <60 mL/min/1.73 m² offers opportunity for earlier renoprotective therapy in individuals with eGFR-associated increased CV death or non-fatal CV event risk.

Anemia is a risk factor for rapid eGFR decline in type 2 diabetes

OBJECTIVE

To investigate the association between anemia and progression of diabetic kidney disease (DKD) in type 2 diabetes.

METHODS

This was a retrospective study. A total of 2570 in-patients with type 2 diabetes hospitalized in Jinan branch of Huashan hospital from January 2013 to October 2017 were included, among whom 526 patients were hospitalized ≥ 2 times with a median follow-up period of 2.75 years. Annual rate of eGFR decline was calculated in patients with multiple admissions. A rate of eGFR decline exceeding -5 ml/min per 1.73 m² per year was defined as rapid eGFR decline. The prevalence of DKD and clinical characteristics were compared between anemia and non-anemia patients. Correlation analysis was conducted between anemia and clinical parameters. Comparison of clinical features were carried out between rapid eGFR decline and slow eGFR decline groups. The risk factors for rapid DKD progression were analyzed using logistic regression analysis.

RESULTS

The prevalence of anemia was 28.2% among the 2570 diabetic patients, while in patients with DKD, the incidence of anemia was 37.8%. Patients with anemia had greater prevalence of DKD, higher levels of urinary albumin-to-creatinine ratio (UACR), serum creatinine, BUN, urine α1-MG, urine β2-MG, urine NAG/Cr, hsCRP, Cystatin C, homocysteine and lower eGFR, as compared to the patients without anemia. Anemia was correlated with age, UACR, eGFR, urinary NAG/Cr, hsCRP and diabetic retinopathy (DR). Logistic regression analysis of 526 patients with type 2 diabetes during the follow-up period showed that anemia was an independent risk factor for rapid eGFR decline.

CONCLUSION

Anemia is associated with worse renal function and is an independent risk factor for rapid eGFR decline in type 2 diabetes.