How to interpret an estimated glomerular filtration rate (eGFR) in 2020?

Relevance of repeated analyses of albuminuria and glomerular filtration rate in African children with sickle cell anaemia

Glomerular hyperfiltration and albuminuria are frequent kidney abnormalities in children with sickle cell anaemia (SCA). However, little is known about their persistence in African SCA children. This prospective study included 600 steady-state SCA children aged 2-18 years from the Democratic Republic of Congo. Participants were genotyped for apolipoprotein L1 (APOL1) risk variants (RVs) and haem oxygenase-1 (HMOX1) GT-dinucleotide repeats. Kidney abnormalities were defined as albuminuria, hyperfiltration or decreased estimated creatinine-based glomerular filtration rate (eGFRcr). At baseline, 247/600 (41.2%) participants presented with kidney abnormalities: 82/592 (13.8%) with albuminuria, 184/587 (31.3%) with hyperfiltration and 15/587 (2.6%) with decreased eGFRcr. After a median follow-up of 5 months, repeated testing was performed in 180/247 (72.9%) available participants. Persistent hyperfiltration and persistent albuminuria (PA) were present in 29.2% (38/130) and 39.7% (23/58) respectively. eGFR normalized in all participants with a baseline decreased eGFRcr. Haemoglobinuria (p = 0.017) and male gender (p = 0.047) were significantly associated with PA and persistent hyperfiltration respectively. APOL1 RVs (G1G1/G2G2/G1G2) were borderline associated with PA (p = 0.075), while HMOX1 long repeat was not associated with any persistent kidney abnormality. This study reveals that a single screening can overestimate the rate of kidney abnormalities in children with SCA and could lead to overtreatment.

Association of impaired kidney function with dementia and brain pathologies: A community-based cohort study

INTRODUCTION

The relationship between impaired kidney function (KF), dementia, and brain pathologies remains unclear.

METHODS

A total of 1354 dementia- and kidney disease-free participants including 895 with normal and 459 with impaired KF were followed from 2002 until 2020 (median [interquartile range]: 5 [2-9]) to detect incident dementia. KF was assessed at baseline and categorized as normal or impaired. Over the follow-up, 453 participants died and underwent autopsies for neuropathological assessment.

RESULTS

Compared to those with normal KF, the hazard ratios (95% confidence intervals [CIs]) of those with impaired KF was 1.48 (1.15, 1.90)/1.44 (1.10, 1.88) for dementia/Alzheimer's dementia. Furthermore, impaired KF was related to a significantly higher burden of cerebral amyloid angiopathy (CAA; odds ratio = 1.96, 95% CI: 1.17, 3.30), but not to other brain pathologies.

DISCUSSION

Impaired KF is associated with an increased risk of dementia and Alzheimer's dementia. CAA may underlie, in part, this association.

HIGHLIGHTS

Impaired kidney function (KF) was associated with higher dementia and Alzheimer's dementia risk. Impaired KF anticipated dementia and Alzheimer's dementia onset by more than 1.5 years. Impaired KF was significantly related to a higher burden of cerebral amyloid angiopathy (CAA) but not to other brain pathologies.

Risk-based versus GFR threshold criteria for nephrology referral in chronic kidney disease

Chronic kidney disease (CKD) and kidney failure are global health problems associated with morbidity, mortality and healthcare costs, with unequal access to kidney replacement therapy between countries. The diversity of guidelines concerning referral from primary care to a specialist nephrologist determines different outcomes around the world among patients with CKD where several guidelines recommend referral when the glomerular filtration rate (GFR) is <30 mL/min/1.73 m2 regardless of age. Additionally, fixed non-age-adapted diagnostic criteria for CKD that do not distinguish correctly between normal kidney senescence and true kidney disease can lead to overdiagnosis of CKD in the elderly and underdiagnosis of CKD in young patients and contributes to the unfair referral of CKD patients to a kidney specialist. Non-age-adapted recommendations contribute to unnecessary referral in the very elderly with a mild disease where the risk of death consistently exceeds the risk of progression to kidney failure and ignore the possibility of effective interventions of a young patient with long life expectancy. The opportunity of mitigating CKD progression and cardiovascular complications in young patients with early stages of CKD is a task entrusted to primary care providers who are possibly unable to optimally accomplish guideline-directed medical therapy for this purpose. The shortage in the nephrology workforce has classically led to focused referral on advanced CKD stages preparing for kidney replacement, but the need for hasty referral to a nephrologist because of the urgent requirement for kidney replacement therapy in advanced CKD is still observed and changes are required to move toward reducing the kidney failure burden. The Kidney Failure Risk Equation (KFRE) is a novel tool that can guide wiser nephrology referrals and impact patients.

CKD prevalence based on real-world data: continuous age-dependent lower reference limits of eGFR with CKD-EPI, FAS and EKFC algorithms

Purpose

Several recent articles discuss the need for a definition of chronic kidney disease (CKD) that embarks age-dependency and its impact on the prevalence of CKD. The relevance is derived from the common knowledge that renal function declines with age. The aim of this study was to calculate age-dependent eGFR lower reference limits and to consider their impact on the prevalence of CKD.

Methods

A real-world data set from patients with inconspicuous urinalysis was used to establish two quantile regression models which were used to calculate continuous age-dependent lower reference limits of CKD–EPI, FAS and EKFC–eGFR based on either single eGFR determinations or eGFR values that are stable over a period of at least 3 months (± 10% eGFR). The derived lower reference limits were used to calculate the prevalence of CKD in a validation data set. Prevalence calculation was done once without and once with application of the chronicity criterion.

Results

Both models yielded age-dependent lower reference limits of eGFR that are comparable to previously published data. The model using patients with stable eGFR resulted in higher eGFR reference limits. By applying the chronicity criterion, a lower prevalence of CKD was calculated when compared to one-time eGFR measurements (CKD–EPI: 9.8% vs. 8.3%, FAS: 8.0% vs. 7.2%, EKFC: 9.0% vs. 7.1%).

Conclusion

The application of age-dependent lower reference intervals of eGFR together with the chronicity criterion result in a lower prevalence of CKD which supports the estimates of recently published work and the idea of introducing age-dependency into the definition of CKD.