Rapidly Progressive Glomerulonephritis Workup

Updated: Jan 10, 2018
  • Author: James W Lohr, MD; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Workup

Laboratory Studies

The most important requirement in the diagnosis of ANCA-associated disease is a high index of suspicion. Rapid diagnosis is essential for organ preservation. Laboratory studies include the following:

  • Complete blood cell count (CBC) with differential: Results are most likely normal, but anemia may be present if the patient has renal failure or is bleeding from the GI tract. Eosinophilia of 13% or greater is suggestive of Churg-Strauss disease.

  • Serum electrolytes, BUN, creatinine, lactate dehydrogenase (LDH), creatine phosphokinase (CPK), and liver function tests: The most common abnormality is an increased serum creatinine level. However, the level can be normal at presentation. Tissue enzyme (ie, LDH, CPK) levels may be elevated if the amount of inflammation is significant enough to result in myalgias.

  • Urinalysis with microscopy: Proteinuria is almost always present but is rarely greater than 2-3 g in 24 hours. Microscopic hematuria is invariably present and may be the only clue to renal disease at presentation. The presence of red cell casts indicates glomerular inflammation and is a very helpful clue.

  • Erythrocyte sedimentation rate: Although a nonspecific finding, the rate is usually elevated with active disease.

  • C-reactive protein: levels are elevated and correspond with disease activity.

  • Antinuclear antibody (ANA) titer: The ANA titer result is not positive in patients with ANCA-associated disease. A high ANA titer should direct the diagnosis toward systemic lupus erythematosus.

  • ANCA with ELISA subtyping: More than 80% of patients with microscopic polyangiitis are ANCA-positive, and most of these demonstrate pANCA with MPO specificity. Of patients with granulomatosis with polyangiitis, 90% are ANCA-positive and most have cANCA with PR3 specificity, especially in pulmonary involvement. However, ANCA type and specificity is not pathognomonic for each of these clinical syndromes because some patients with granulomatosis with polyangiitisare pANCA-positive and some patients with microscopic polyangiitis are cANCA-positive. Simon and colleagues investigated the presence of anti-pentraxin 3 (PTX3)- autoantibodies (aAbs) in the sera of antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) patients and found that anti-PTX3 aAbs were present in nearly 40% of patients studied including in patients without detectable MPO and PR3 ANCA. [5]

  • Cryoglobulins: The symptoms of cryoglobulinemia are very similar to those of ANCA-related disease. However, in persons with ANCA-related diseases, the cryoglobulin titer result should be negative.

  • Hepatitis profile: ANCA-associated disease is not associated with hepatitis. However, hepatitis B is associated with polyarteritis nodosa and hepatitis C is associated with mixed cryoglobulinemia.

  • Urine and serum protein electrophoresis: Perform this in any middle-aged or elderly person presenting with rapidly progressive glomerulonephritis to exclude the presence of light-chain disease or overt multiple myeloma as a cause of the clinical findings.

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Imaging Studies

See the list below:

  • A renal ultrasound should be done to rule out obstructive uropathy in any patient with acute renal failure.

  • In patients with rapidly progressive glomerulonephritis, a renal ultrasound is done to establish the presence of 2 functioning kidneys prior to a percutaneous renal biopsy.

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Procedures

See the list below:

  • Because the sensitivity and the specificity of ANCA testing for pauci-immune glomerulonephritis is only 80-90%, a renal biopsy is recommended to be performed on patients with rapidly progressive glomerulonephritis to establish a definite diagnosis and to determine the severity of the disease. The initiation of therapy should not be delayed for biopsy results to be obtained.

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Histologic Findings

Renal biopsy specimens show a diffuse, proliferative, necrotizing glomerulonephritis with crescent formation.

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