Which laboratory finding supports a diagnosis of primary (idiopathic) membranous nephropathy rather than secondary membranous nephropathy?
- A Low serum complement C3
- B Serum anti-phospholipase A2 receptor antibody positivity ✓
- C Elevated antinuclear antibody titre
- D Positive hepatitis B surface antigen
Correct answer: B. Serum anti-phospholipase A2 receptor antibody positivity
Explanation
Anti-PLA2R antibodies are found in about 70 to 80 percent of patients with primary membranous nephropathy and are not present in secondary forms such as lupus-associated, hepatitis A-associated or drug-induced disease. Their detection therefore supports idiopathic disease and can spare a biopsy in typical presentations. Low C3 points to immune complex GN such as lupus, while ANA and HBsAg suggest secondary causes of membranous nephropathy.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.