Approach to the diagnosis of membranous nephropathy

MN: membranous nephropathy; HIV: human immunodeficiency virus; SFLC: serum free light chain; SPEP: serum protein electrophoresis; PLA2R: phospholipase A2 receptor; eGFR: estimated glomerular filtration rate; Ag: antigen; ANA: antinuclear antibodies; ELISA: enzyme-linked immunoabsorbant assay; IFA: immunofluorescence assay.

* MN should be suspected in all adult patients who present with features of the nephrotic syndrome, such as unexplained proteinuria and edema or weight gain.

¶ In patients at high risk for lung malignancy (eg, history of smoking or asbestos exposure), computed tomography of the chest should be performed.

Δ Commercial assays available for anti-PLA2R include an IFA and an ELISA. Assessment of seropositivity for anti-PLA2R can vary depending upon the specific assay used for its detection and quantitation and upon the cutoff value that defines a positive result. Refer to UpToDate content for more details on defining a positive serum anti-PLA2R antibody result.

◊ Evidence of secondary disease includes the following: positive testing for ANA and anti-dsDNA, hepatitis B or C, or HIV; low serum complement levels; abnormal SFLCs or SPEP; or radiographic findings consistent with sarcoidosis. Atypical features include red blood cell or white blood cell casts on examination of the urinary sediment.

§ If a kidney biopsy cannot be performed (due to patient preference, lack of availability, or contraindication to biopsy), serum anti-PLA2R antibody testing can be repeated in 3 to 4 months since some patients with an initially negative serum antibody test may have delayed seroconversion. If repeat serum anti-PLA2R testing is negative, a kidney biopsy should be performed, if possible.