How can a primary care physician recognize immunoglobulin A (IgA) nephropathy and what interventions can be performed in primary care?

Recognition and Management of IgA Nephropathy in Primary Care

Primary care physicians should suspect IgA nephropathy in any adult with persistent microscopic hematuria combined with proteinuria ≥0.5 g/day, and refer immediately for nephrology evaluation and kidney biopsy, as this is the only definitive diagnostic test 1.

Clinical Recognition: Key Presentations to Identify

High-Suspicion Clinical Scenarios

IgAN presents in several distinct patterns that should trigger immediate consideration:

• Synpharyngitic hematuria (30% of cases): Visible blood in urine occurring within 1-2 days of upper respiratory or gastrointestinal infection—this is highly characteristic of IgAN 2
• Incidental detection (60% of cases): Asymptomatic microscopic hematuria or proteinuria discovered on routine urinalysis 2
• Nephritic syndrome: Combination of hematuria, proteinuria, hypertension, and declining kidney function
• Nephrotic syndrome (<5%): Heavy proteinuria with edema and hypoalbuminemia 2
• Rapidly progressive glomerulonephritis (<5%): Acute kidney injury with active urinary sediment 2

Essential Urinalysis Findings

Look specifically for:

• Dysmorphic red blood cells (acanthocytes) on microscopy
• Red blood cell casts—these indicate glomerular bleeding and are pathognomonic for glomerulonephritis 3
• Persistent microscopic hematuria with proteinuria

Critical pitfall: Do not dismiss persistent microscopic hematuria as benign, especially when combined with any degree of proteinuria. The 2025 KDIGO guidelines now advocate for more liberal kidney biopsy policies, recommending biopsy consideration in all adults with proteinuria ≥0.5 g/day when IgAN is suspected 1.

Initial Workup in Primary Care

Immediate Laboratory Assessment

When IgAN is suspected, order:

1. Quantify proteinuria: 24-hour urine collection or spot urine protein-to-creatinine ratio (PCR)
2. Serum creatinine and eGFR: Assess baseline kidney function 3
3. Urinalysis with microscopy: Specifically request evaluation for dysmorphic RBCs and casts
4. Blood pressure measurement: Hypertension is common and prognostically important

Exclude Secondary Causes

Before referral, screen for conditions that can cause secondary IgA deposition:

• Autoimmune diseases: ANA, complement levels (C3, C4) to exclude lupus nephritis
• Chronic infections: Hepatitis B and C, HIV serology 1
• Inflammatory bowel disease: Clinical history
• Cirrhosis: Liver function tests
• Celiac disease: If clinically indicated 2, 4

Important note: There are no validated serum or urine biomarkers for diagnosing IgAN—kidney biopsy remains the gold standard 1.

What Primary Care Can Initiate Before Nephrology Referral

Immediate Interventions (Start These Now)

While awaiting nephrology consultation, primary care physicians can and should initiate:

1. Blood Pressure Control

• Target: <120/70 mmHg (this is the new, more aggressive target from 2025 guidelines) 2
• Start with ACE inhibitor or ARB for dual benefit of BP control and proteinuria reduction
• Titrate to maximum tolerated dose

2. Lifestyle Modifications

• Dietary sodium restriction to <2 g/day (<90 mmol/day) 3, 2
• Smoking cessation: Mandatory—smoking accelerates progression
• Weight control and regular exercise 2
• Avoid NSAIDs—these worsen kidney function

3. RAS Blockade

• Initiate ACE inhibitor or ARB regardless of blood pressure if proteinuria is present
• This is foundational supportive care that should not be delayed 5, 6

What NOT to Do in Primary Care

Do not initiate immunosuppressive therapy (corticosteroids, targeted-release budesonide, or other immunomodulators)—these require nephrology expertise for appropriate patient selection, dosing, and monitoring of serious adverse effects 1, 4.

Urgent Nephrology Referral Criteria

Refer immediately (within days to weeks) for:

• Any proteinuria ≥0.5 g/day with suspected IgAN for kidney biopsy consideration 1
• Rapidly declining kidney function (rising creatinine)
• Nephrotic-range proteinuria (>3.5 g/day)
• Acute kidney injury with active urinary sediment
• Visible hematuria with proteinuria or declining kidney function

The 2025 KDIGO guidelines emphasize early diagnosis and prompt treatment, noting that lower proteinuria thresholds now warrant biopsy because even modest proteinuria (0.5-1.0 g/day) carries significant lifetime risk of kidney failure 1.

Prognosis Communication

Inform patients that:

• Up to 50% develop kidney failure within 10 years without appropriate treatment 2
• IgAN is the most common immune-mediated glomerular disease worldwide
• New targeted therapies are now available that can significantly alter disease trajectory
• Early detection and treatment are critical for preventing progression

Long-term Primary Care Role

After nephrology establishes diagnosis and treatment plan:

• Monitor proteinuria regularly: Treatment goal is now <0.5 g/day, ideally <0.3 g/day 1
• Track kidney function: eGFR should decline <1 mL/min/year with effective treatment 1
• Maintain BP control: Continue aggressive BP management
• Reinforce lifestyle modifications: Ongoing support for sodium restriction, weight management
• Monitor for treatment complications: If patient is on immunosuppression, watch for infections and metabolic effects
• Coordinate care: Regular communication with nephrology, especially if proteinuria increases or kidney function declines

The primary care physician's role is pivotal in early detection—recognizing the combination of hematuria and proteinuria, initiating basic supportive care, and ensuring timely nephrology referral for definitive diagnosis and specialized treatment 7.