Tests
1st tests to order
urinalysis
Test
Proteinuria will result in dipstick positive for protein.
Result
positive for protein; bland sediment, lipid droplets occasionally
urine protein to creatinine ratio
Test
Spot urine test may be performed initially. This may be followed by a 24-hour urine collection in uncertain cases.
Result
>3.5 is consistent with nephrotic syndrome
serum BUN
Test
Abnormal suggests renal dysfunction and will help guide treatment.
Result
normal or elevated
serum creatinine
Test
Elevation suggests renal impairment. Value can be used to calculate the creatinine clearance.
Result
normal or elevated
creatinine clearance
Test
Calculated from the serum creatinine when age, sex, and ethnicity are taken into account. [ Glomerular Filtration Rate Estimate by the IDMS-Traceable MDRD Study Equation Opens in new window ]
Result
normal or decreased
serum albumin
Test
Hypoalbuminemia of <3 g/dL is consistent with nephrotic syndrome.
Result
usually low
lipid profile
Test
Hyperlipidemia is seen in nephrotic syndrome due to increased synthesis by the liver and urinary loss of lipid-regulating proteins.
Result
normal or elevated
Tests to consider
serum or plasma LFTs
Test
Abnormal may suggest underlying hepatitis B or C.
Result
elevated with hepatitis
hepatitis B and C serology
Test
Acute or chronic infection can be associated with MN.
Result
positive with hepatitis infection
antinuclear antibody, antidouble-stranded DNA
Test
High titers suggest underlying systemic lupus erythematosus (SLE).
Result
elevated in SLE
complement levels
Test
Typically C3, C4, CH50.
Result
low in SLE
anti-SS-B, anti-SS-A
Test
Sjogren syndrome may cause secondary MN.
Result
positive in Sjogren syndrome
anti-PLA2R autoantibodies
Test
A high proportion of patients with primary MN have circulating antibodies to M-type phospholipase A2 receptor (PLA2R), a transmembrane protein located on podocytes.[8][9]
PLA2R appears to be a major antigen in the pathogenesis of primary MN in humans.
A positive test for anti-PLA2R autoantibodies does not rule out secondary causes, such as hepatitis or lupus.
Result
positive test is suggestive of primary MN
anti-Thrombospondin type 1 domain–containing 7A (THSD7A) autoantibodies
Test
About 10% of patients with primary MN have antibodies circulating autoantibodies to THSD7A but not to PLA2R.[19]
Result
positive test is suggestive of primary MN
renal ultrasound with renal artery Doppler study
Test
Helps to exclude other pathologies and causes of renal dysfunction.
Specifically, ultrasound is useful to assess the size of the kidneys to rule out hydronephrosis; evaluate systolic arterial pressures to rule out renal artery stenosis; and evaluate resistive indices for microvascular disease.
Result
variable
renal biopsy
Test
Referral to specialist for consideration of renal biopsy. Definitive diagnosis based on biopsy findings; the most sensitive and specific test.
Light microscopy: diffuse thickening of glomerular basement membrane (GBM) throughout all glomeruli in absence of significant hypercellularity.
Immunofluorescence microscopy: diffuse granular pattern of IgG, with C3 along GBM.
Electron microscopy: stage 1: light microscopy normal; small electron-dense subepithelial deposits with segmental distribution; focal foot process effacement is a constant. Stage 2: subepithelial electron-dense deposits with small GBM extensions (spikes); GBM spikes seen with silver staining (segments of GBM between dense deposits). Stage 3: dense deposits are incorporated in GBM; thickening of GBM detectable by light microscopy. Stage 4: markedly thickened GBM with initial electron-dense deposits now electron lucent.[21]
Result
characteristic changes with light, immunofluorescence, and electron microscopy
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