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The clinical diagnosis criteria and staging of diabetic kidney disease (DKD)

Can Diabetes Cause Kidney Disease

Along with accurate diagnosis, are of significant importance for rational drug use, delaying the progression of diabetic kidney disease, and preventing complications. The “Guidelines for the Diagnosis and Treatment of Diabetic Kidney Disease in Traditional Chinese and Western Medicine” provide detailed descriptions of clinical diagnostic recommendations and staging for DKD.

Clinical Diagnostic Recommendations for DKD

Exclusion of Non-Diabetic Kidney Diseases

The guidelines from the American Diabetes Association (ADA) in 2022, the Kidney Disease Improving Global Outcomes (KDIGO) organization in 2020, and the Asia-Pacific Society of Nephrology (APSN) in 2020 all assert that Diabetic Kidney Disease (DKD) refers to the occurrence of proteinuria and/or renal function decline in diabetic patients, with the exclusion of kidney damage caused by other underlying reasons.

In actual clinical diagnoses of DKD patients, a subset frequently presents with coexisting non-diabetic kidney diseases (NDKD). This may include scenarios where diabetes or DKD coexists with conditions like IgA nephropathy, membranous nephropathy, lupus nephritis, hepatitis B-related nephritis, vasculitis-related kidney injury, and even renal amyloidosis.

A meta-analysis incorporating 48 studies, involving 4,876 cases of kidney biopsies in DKD patients, revealed a non-diabetic kidney disease (NDKD) occurrence rate of approximately 36.9%. The occurrence rate of diabetic nephropathy (DN) combined with non-diabetic kidney disease (NDKD) was about 19.7%. Consequently, the guidelines recommend that before diagnosing DKD in type 2 diabetes patients, a comprehensive assessment, incorporating medical history, clinical manifestations, relevant laboratory tests, especially serum immunology, and imaging examinations, should be conducted to rule out non-diabetic kidney diseases (NDKD). Only after excluding NDKD can a diagnosis of DKD be confirmed.

Measurement of Urinary Albumin/Creatinine Ratio (UACR) and eGFR

Internationally, guidelines from organizations such as the American Diabetes Association (ADA) in 2022, the Kidney Disease Outcomes Quality Initiative (KDOQI) in 2007, the 2021 Clinical Diagnosis and Treatment Guidelines for Diabetic Kidney Disease, and the 2021 edition of the Chinese Guidelines for the Prevention and Treatment of Diabetic Kidney Disease recommend the repetition of UACR and eGFR measurements three times within a 3-6 month period. A clinical diagnosis of Diabetic Kidney Disease (DKD) is considered when, during these repeated measurements, UACR increases (>30mg/g) and/or eGFR falls below 60mL/min/1.73m² on two or more occasions. However, it is important to note that factors such as intense physical activity, infection, fever, congestive heart failure, etc., can cause transient proteinuria.

Taking into account domestic and international guidelines, after excluding factors causing transient proteinuria, a diagnosis of DKD can be established if, during the 3-6 month period with three repeated measurements, UACR increases (>30mg/g) and/or eGFR is consistently below 60mL/min/1.73m² on two or more occasions.

In clinical practice, some DKD patients may not meet the diagnostic criteria based on urine tests, but their eGFR is below 60mL/min/1.73m². The 2021 Clinical Diagnosis and Treatment Guidelines for Diabetic Kidney Disease, the Chinese Guidelines for the Prevention and Treatment of Diabetic Kidney Disease (2021 edition), and the 2022 ADA guidelines suggest that after excluding factors such as infection, obstructive kidney disease, medications, malignant hypertension, and other causes of acute kidney injury, a diagnosis of normoalbuminuric diabetic kidney disease (NADKD) can be made if, during the 3-6 month period with three repeated measurements, urine tests are normal but eGFR remains below 60mL/min/1.73m² on two or more occasions.

In a 2021 meta-analysis of 31 studies (including 18 cross-sectional studies, 11 cohort studies, and 2 case-control studies), the overall prevalence of normoalbuminuric diabetic kidney disease (NADKD) in patients with type 2 diabetes and chronic kidney disease (CKD) was 45.6%. Within the DKD patient population, the prevalence of NADKD was 24.7%. A long-term follow-up study also found that regardless of proteinuria, diabetic patients with CKD stage 3 or later could experience varying degrees of further decline in kidney function after 10 years.

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Clinical Stages of DKD

Clinical Stages of Type 1 Diabetic Kidney Disease (T1DKD)

In 1983, Danish scholar Mogensen proposed a clinical staging method for Type 1 Diabetic Kidney Disease (T1DKD), which is outlined as follows:

Stage I: Hyperfiltration stage, characterized by increased glomerular filtration.

Stage II: Normoalbuminuric stage, where albuminuria is within normal range.

Stage III: Early DKD stage, marked by a gradual increase in urinary albumin excretion to a range of 20-200μg/min.

Stage IV: Clinical DKD stage, defined by urinary albumin excretion exceeding 200μg/min or proteinuria surpassing 500mg/day, accompanied by a continuous decline in glomerular filtration rate (GFR).

Stage V: End-stage renal failure, where GFR is less than 10mL/min.

The natural history of Type 1 Diabetic Kidney Disease (T1DKD) is relatively well-established, and both domestic and international recommendations endorse the adoption of this method for clinical staging of patients with Type 1 Diabetic Kidney Disease (T1DKD).

Clinical Staging of Type 2 Diabetic Kidney Disease (T2DKD)

There is currently no unified understanding of the clinical staging for Type 2 Diabetic Kidney Disease (T2DKD). While some perspectives suggest that the Mogensen staging may also be applicable to T2DKD, the condition in T2DKD patients is often more insidious, making early detection challenging. Additionally, some patients may already exhibit proteinuria or other complications at the time of DKD diagnosis, possibly entering Mogensen Stage III. In comparison to Type 1 Diabetic Kidney Disease, T2DKD patients tend to be older at the onset, exhibit greater heterogeneity in renal pathology, and show more diverse patterns in urinary albumin excretion rates. Therefore, the Mogensen staging method is not as suitable for the clinical staging of T2DKD.

Some scholars have suggested a classification for Type 2 Diabetic Kidney Disease (T2DKD) into three stages:

Early Stage (Implicit or Microalbuminuria Stage): Characterized by subtle or microalbuminuria.

Intermediate Stage (Persistent Proteinuria Stage): Marked by sustained proteinuria.

Late Stage (Renal Failure Stage): Representing advanced kidney failure.

While this staging classification may assist in the management of diabetic kidney disease, it falls short in reflecting the actual level of renal function.

The clinical staging of Diabetic Kidney Disease (DKD) is recommended to be assessed using the G/A classification method, as advocated by the 2012 Kidney Disease: Improving Global Outcomes (KDIGO) Clinical Practice Guidelines for Diabetes and Chronic Kidney Disease (CKD), the consensus of experts from the Endocrinology Branch of the Chinese Medical Association, and the 2021 Clinical Diagnosis and Treatment Guidelines for Diabetic Kidney Disease in China, developed by the Kidney Disease Branch of the Chinese Medical Association.

In this classification:

G represents eGFR levels (glomerular filtration rate) and is divided into G1 to G5 categories:

G1: eGFR ≥ 90 mL/min/1.73m²

G2: eGFR 60-89 mL/min/1.73m²

G3: eGFR 30-59 mL/min/1.73m²

G4: eGFR 15-29 mL/min/1.73m²

G5: eGFR < 15 mL/min/1.73m²

A represents albuminuria levels and is divided into A1 to A3 categories:

A1: UACR < 30mg/g

A2: UACR 30-300mg/g

A3: UACR > 300mg/g

For example, if a patient is clinically diagnosed with DKD in G3A3 stage, it indicates that the patient has CKD in stage 3, with proteinuria exceeding 300mg/g.

Currently, both domestic and international nephrology and endocrinology specialists consider the G/A staging method to be more precise and practical compared to the traditional Mogensen staging. This method not only aids in the assessment of the functional and damage extent of DKD but also helps predict the risk of patients progressing to end-stage kidney disease. Furthermore, it facilitates the development of effective management and prevention measures for DKD in clinical practice.

However, it’s important to note that the G/A staging method has a relatively narrow range for proteinuria quantification (UACR < 30mg/g to >300mg/g). Nephrologists often encounter DKD patients with urine protein levels exceeding 3000mg/g. Therefore, we believe that the G/A staging method is more suitable for early and intermediate-stage DKD patients, while further discussion is needed on how to stage patients with significant proteinuria in conjunction with renal function.

References:糖尿病肾脏疾病中西医结合诊疗指南

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