Initial Testing for CKD: Confirmation, Etiology, Risk, and Complications
Test all at-risk individuals with both serum creatinine (to calculate eGFR) and urine albumin measurement—these two tests together confirm CKD, stage disease severity, and stratify cardiovascular and progression risk. 1
Core Diagnostic Tests
The 2024 KDIGO guidelines establish a clear testing framework:
Primary Tests (Required for All Suspected CKD)
- Serum creatinine → calculate estimated GFR (eGFR)
- Urine albumin-to-creatinine ratio (ACR)
- Urinalysis (to detect hematuria, cellular casts, other abnormalities)
These three tests accomplish multiple objectives simultaneously: they confirm CKD presence, enable staging, assess progression risk, and guide treatment decisions 1. The combination of eGFR and albuminuria provides both diagnostic confirmation and prognostic stratification for cardiovascular disease, CKD progression, and mortality risk 2.
Blood Pressure Measurement
Measure blood pressure at every visit, as hypertension is both a cause and complication of CKD, and BP control is nephroprotective 3, 4.
Establishing Etiology
Once CKD is confirmed, determine the underlying cause through:
History-Based Assessment
- Diabetes mellitus status (most common cause)
- Hypertension history and control
- Cardiovascular disease history
- Family history of kidney disease (polycystic kidney disease, hereditary nephritis)
- Medication exposure (NSAIDs, lithium, calcineurin inhibitors)
- Systemic disease symptoms (lupus, vasculitis)
Targeted Additional Testing Based on Clinical Presentation
High-yield glomerulonephritis testing when any of these present 5:
- Abnormal urine sediment (RBC casts, dysmorphic RBCs)
- 3+ or greater hematuria on dipstick
- Proteinuria >500 mg/g
High-yield paraprotein testing when any of these present 5:
- History of monoclonal disease
- High CKD progression risk
- Hypercalcemia
- Hemoglobin <10.6 g/dL
Renal ultrasound indicated for:
- Prior history of hydronephrosis or renal artery stenosis
- Suspected obstruction
- Asymmetric kidney disease
- Rapid GFR decline
Risk Stratification
The eGFR and albuminuria levels directly determine:
- Progression risk to kidney failure
- Cardiovascular disease risk (CKD is a CVD equivalent)
- Mortality risk
- Timing of nephrology referral 1
Detecting Treatable Complications
Once eGFR falls below 60 mL/min/1.73m² (Stage 3 or higher), assess for:
Metabolic Complications
- Hemoglobin (anemia screening)
- Calcium and phosphorus (mineral bone disorder)
- Parathyroid hormone (PTH) (secondary hyperparathyroidism)
- Bicarbonate (metabolic acidosis)
- Potassium (hyperkalemia risk)
These complications should be assessed and treated in primary care—do not delay until nephrology referral 6.
Additional Cardiovascular Risk Assessment
- Lipid panel (aggressive management warranted given high CVD risk)
- Hemoglobin A1c if diabetic (tight glycemic control slows progression)
Confirmatory Testing
Critical caveat: If initial testing shows abnormal creatinine/eGFR or albuminuria, obtain confirmatory testing before diagnosing CKD 1. CKD requires persistence of abnormalities for at least 3 months to distinguish from acute kidney injury or transient proteinuria 6, 2.
Nephrology Referral Triggers
Refer when 2:
- eGFR <30 mL/min/1.73m²
- Urine ACR >300 mg/g (or protein-to-creatinine ratio >500 mg/g)
- Rapid loss of kidney function
- Uncertain etiology requiring specialized evaluation
The algorithmic approach prioritizes early detection through simple, widely available tests (creatinine, urine albumin, urinalysis) that simultaneously confirm disease, stage severity, and identify those needing intervention—maximizing the opportunity to implement disease-modifying therapies like SGLT2 inhibitors that dramatically improve outcomes 7.