Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (532 page)

   Laboratory Findings

   Marked proteinuria; nephrotic syndrome is found in many patients.

   Microscopic hematuria may be present.

   Autoantibodies against phospholipase-A2 receptor (PLA2R-Ab), mostly of the IgG4 class, can be found in 70% of patients with primary membranous GN and levels correlate with the clinical course and proteinuria.

   Definitive diagnosis is by renal biopsy showing diagnostic findings by light, immunofluorescence, and electron microscopy.

Suggested Reading

Floege J. Primary glomerulonephritis: a review of important recent discoveries.
Kidney Res Clin Pract.
2013;32(3):103–110.

GLOMERULONEPHRITIS, POSTINFECTIOUS

   Definition

   Postinfectious GN (PIGN) occurs after infection, usually with a nephritogenic strain of group A β-hemolytic
Streptococcus
(poststreptococcal GN [PSGN]).

   It is the most common glomerular disorder in children between 5 and 15 years.

   Pathogenesis is thought to be related to deposits of immune complexes in the glomerular basement membrane causing glomerular damage. Only 1–2% of cases progress to chronic GN.

   Laboratory Findings

   Evidence of infection with group A β-hemolytic
Streptococcus
by throat culture.

   
Serologic findings
: Anti-streptolysin O (ASO) is the most common laboratory test to confirm recent streptococcal infection. ASO titers remain elevated for several months in 50–80% of patients. Anti- DNase B is anther serologic test to confirm a previous group A streptococcal infection.

   
Urinalysis: