OSCE — IgA Nephropathy

Station instructions (to candidate)

A 24-year-old man presents to the outpatient department with two episodes of painless, tea-coloured urine over the past month, each lasting two days and occurring one to two days after a sore throat. He has no past medical history. Examine and manage.

Vital signs: BP 146/92 mmHg, pulse 78/min, afebrile, no oedema.

Examiner checklist (assess each — done / partial / not done)

History (2 min)

• Elicits the timing of haematuria relative to the sore throat (synpharyngitic — within 1 to 2 days)
• Asks about number of episodes, visible clots, flank pain, frothy urine, oedema
• Past history: recent infections, sore throat, skin infection, drug/NSAID use
• Family history of renal disease, deafness (Alport), haematuria

Examination (2 min)

• Fluid status and blood pressure (hypertension is a marker and treatment target)
• Looks for oedema, signs of volume overload (JVP, basal crackles)
• Screens for secondary causes / mimics: stigmata of chronic liver disease, purpura (IgA vasculitis), rash and arthritis (lupus)
• Cardiovascular and abdominal examination (flank tenderness)

Investigations (2 min)

• Urinalysis: dysmorphic red cells and red-cell casts (glomerular haematuria), proteinuria
• Quantifies proteinuria: spot urine protein-to-creatinine ratio
• Bloods: serum creatinine and eGFR, albumin, serum IgA, complement C3 and C4 (normal in IgA nephropathy)
• Serology to exclude mimics: ANA, anti-dsDNA, ANCA, anti-GBM, ASO titre, hepatitis B/C and HIV
• States the indication for renal biopsy (proteinuria over 0.5 to 1 g/day, rising creatinine, hypertension or atypical features)

Diagnosis (1 min)

• States IgA nephropathy (Berger disease) — commonest primary GN; synpharyngitic haematuria, normal complement
• Offers the differential and key discriminator: post-streptococcal GN (1 to 3 week latent period, low C3)

Management (2 min)

• Foundation: ACE inhibitor or ARB to reduce proteinuria (blood pressure under 130/80)
• Adds an SGLT2 inhibitor for proteinuric CKD (EMPA-KIDNEY)
• High-risk / persistent proteinuria: targeted-release budesonide and selective steroids (TESTING/STOP-IgAN); RPGN -> cyclophosphamide plus glucocorticoids
• Lifestyle: salt restriction, smoking cessation, weight management
• Recognises red flags: rising proteinuria, hypertension, falling GFR (escalate); crescents on biopsy (urgent immunosuppression)

Key questions to ask the candidate

1. What is the significance of haematuria within one day of a sore throat? — Synpharyngitic, classic for IgA nephropathy; contrast with post-streptococcal GN (1 to 3 week latent period).
2. What would you expect the serum complement to be? — Normal in IgA nephropathy (low C3 in post-strep GN and lupus).
3. What does the biopsy show, and what is the MEST-C score? — Dominant mesangial IgA on immunofluorescence; MEST-C (Mesangial, Endocapillary, Segmental sclerosis, Tubular atrophy/interstitial fibrosis, Crescents); T lesion is the strongest predictor of progression.
4. What is the foundation of treatment? — ACE inhibitor/ARB plus an SGLT2 inhibitor to reduce proteinuria; blood pressure under 130/80.

Common errors to flag

• Confusing IgA nephropathy with post-streptococcal GN on timing.
• Forgetting the ACE inhibitor/ARB (the antiproteinuric backbone) and the SGLT2 inhibitor.
• Over-using immunosuppression (ignoring TESTING infection risk and the STOP-IgAN negative result).
• Missing a rapidly progressive (crescentic) course that needs urgent cyclophosphamide plus glucocorticoids.
• Failing to biopsy when proteinuria rises above 0.5 to 1 g/day.