When can Chronic Kidney Disease (CKD) be diagnosed?

When Can Chronic Kidney Disease Be Diagnosed?

CKD is diagnosed when abnormalities in kidney structure or function persist for at least 3 months, confirmed by either eGFR <60 mL/min/1.73 m², albuminuria (ACR ≥30 mg/g), or other markers of kidney damage present on two separate measurements at least 3 months apart. 1, 2

Diagnostic Criteria

CKD requires persistence of abnormalities for ≥3 months with any of the following 1, 2:

• eGFR <60 mL/min/1.73 m² on two separate occasions at least 3 months apart 1, 2
• Albuminuria (ACR ≥30 mg/g) confirmed on two measurements at least 3 months apart 1, 2
• Other markers of kidney damage including urine sediment abnormalities, structural abnormalities on imaging, histological abnormalities, or history of kidney transplantation, present for ≥3 months 2

Why the 3-Month Requirement Matters

The 3-month persistence requirement is critical because measurements can vary significantly within individuals over time due to temporary factors 1. A single abnormal test overestimates CKD prevalence by approximately 25% compared to using two confirmatory tests 3. This prevents misdiagnosis from transient causes such as:

• Volume depletion 1
• Acute illness 4
• Medication effects 4
• Laboratory variability 3

Screening Approach by Population

For Patients with Type 2 Diabetes

Screen immediately at diagnosis with both spot urine ACR and eGFR, then annually thereafter 1. CKD may already be present at the time of type 2 diabetes diagnosis, unlike type 1 diabetes where screening begins 5 years after diagnosis 1, 2.

For Patients with Type 1 Diabetes

Screen annually starting 5 years after diagnosis with both spot urine ACR and eGFR 1.

For All Adults ≥60 Years or with Hypertension/Cardiovascular Disease

Screen with both eGFR and urine ACR at baseline, as these populations have substantially elevated CKD risk 1, 4.

Laboratory Testing Requirements

Initial Assessment

Measure both of the following simultaneously 1, 2:

• Serum creatinine with eGFR calculation using the CKD-EPI equation (2021 version without race term) 1, 2
• Spot urine albumin-to-creatinine ratio (ACR) in a random urine sample 1

Confirmatory Testing

If either test is abnormal, repeat both measurements after at least 3 months to confirm persistence 1, 2. Review all available historical laboratory data to establish chronicity 2.

Special Consideration for Borderline eGFR

For patients with eGFR 45-59 mL/min/1.73 m² without albuminuria or other markers of kidney damage, consider measuring serum cystatin C to confirm CKD diagnosis 1. Two-thirds of patients with creatinine-based eGFR <60 mL/min/1.73 m² will have cystatin C-based eGFR <60 mL/min/1.73 m², and these patients have markedly elevated risks for death, cardiovascular disease, and end-stage renal disease 1.

Common Diagnostic Pitfalls to Avoid

Don't Rely on Serum Creatinine Alone

Even a "normal" serum creatinine of 100 μmol/L can correspond to eGFR as low as 40 mL/min/1.73 m² in elderly females, meaning 46.5% of patients with creatinine 100 μmol/L have stage 3 CKD when using MDRD eGFR 5. Always calculate eGFR rather than relying on creatinine values 1, 2.

Don't Diagnose from a Single Measurement

Using only one screening test overestimates CKD prevalence by approximately 25% regardless of which equation is used 3. Always confirm with a second measurement at least 3 months later 1, 2, 3.

Don't Assume Normal Kidney Size Excludes CKD

Normal-sized kidneys on imaging do not exclude CKD, particularly in diabetic nephropathy, minimal change disease, or early focal segmental glomerulosclerosis 6, 2. Diagnosis is based on laboratory parameters, not imaging 6, 2.

Don't Use Albumin Concentration Without Creatinine Correction

Measuring spot urine albumin alone without simultaneously measuring urine creatinine is inadequate 1. Always use the albumin-to-creatinine ratio (ACR) in a random spot urine sample 1.

Clinical Context for Diagnosis

Diabetic Kidney Disease

Typically develops after 10 years in type 1 diabetes but may be present at diagnosis of type 2 diabetes 1, 6. The classic presentation includes long-standing diabetes duration, retinopathy, and albuminuria, but reduced eGFR without albuminuria is increasingly common in both type 1 and type 2 diabetes 1, 6.

When to Suspect Alternative Causes

Consider kidney biopsy or nephrology referral for uncertainty about etiology when 1:

• CKD presents without typical diabetic pattern (e.g., no retinopathy, rapid progression, active urine sediment) 1
• Rapidly progressing kidney disease 1
• Up to 30% of patients with presumed diabetic kidney disease have other causes on biopsy 6

Post-Diagnosis Actions

Once CKD is diagnosed with confirmed persistence ≥3 months 1, 2:

• Initiate evidence-based treatments immediately including SGLT2 inhibitors, ACE inhibitors/ARBs for albuminuria, and blood pressure optimization 1
• Monitor at least annually with repeat eGFR and ACR measurements 1, 2
• Refer to nephrology if eGFR <30 mL/min/1.73 m², continuously increasing albuminuria, continuously decreasing eGFR, or uncertainty about etiology 1, 6