AAAAA
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What is the screening test for Wegner granulomatosis?
A. C-ANCA
B. P-ANCA
C. PR3
D. C and A
E. C and B
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| abhi01
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C-ANCA
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| bozhenka
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D
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| AAAAA
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D
Do the PR3 first and then if positive go ahead to do the C-ANCA !
bravo !
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| babli
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Antineutrophilic cytoplasmic antibodies
Typically, ANCA are demonstrated by immunofluorescence testing of patient serum incubated with ethanol-fixed normal human neutrophils.
Two types of antibodies are identified. C-ANCA stain the cytoplasm diffusely and are directed against antigen serine proteinase.
Wegener granulomatosus (WG). Staining for antineutrophil cytoplasmic antibody (ANCA) by indirect immunofluorescence shows heavy cytoplasmic staining (C-ANCA), whereas nuclei are nonreactive
P-ANCA usually are directed against myeloperoxidase.
Wegener granulomatosus (WG). Perinuclear antineutrophil cytoplasmic antibody (P-ANCA) staining pattern by indirect immunofluorescence shows perinuclear staining, whereas cytoplasm is nonreactive.
Measurement of ANCA by immunoblotting techniques or enzyme-linked immunoassay is more accurate than immunofluorescence. Anti-MPO antibodies are particularly important because P-ANCA directed against non-MPO molecules such as elastase, lactoferrin, and others may occur in a variety of nonvasculitic disorders.
Almost all patients with active systemic WG have a positive ANCA, commonly directed against PR3. Approximately 80-95% of all ANCA found in patients with WG are C-ANCA/anti-PR3. Most of the remaining 5-20% are P-ANCA–positive with antibodies directed against MPO. The diagnostic accuracy of ANCA becomes greater in patients with the classic presentation, where C-ANCA has a 98% posttest probability of predicting WG.
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| AAAAA
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One of the best well known rheumatologist, Dr.Clement J. Michets Jr. Professor of Rheumatology, Mayo Clinic School of medicine, Rochester, Minnesota taught me about testing of WG.
I did not learnt that in any texts or internet !
Mayo clinic is the clinic for tx of WG ! mayo Clinic is also one of the first to make the diagnosis of WG !!
I learnt that from clinical experience !!!
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| AAAAA
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However, ANCA alone are insufficient for establishing or excluding a diagnosis of Wegener's granulomatosis because their sensitivity decreases in cases of limited or inactive Wegener's granulomatosis. Moreover, ANCA are associated with other diseases, such as microscopic polyangiitis; Churg-Strauss syndrome; rheumatic diseases, such as rheumatoid arthritis and lupus; gastrointestinal illnesses, such as ulcerative colitis and regional enteritis. They are also associated with drugs such as hydralazine or minocycline
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| Jinx
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Two lab tests that are fairly specific for WG are the ANCA test and the anti-PR3. Usually an anti-MPO is ordered with the anti-PR3.
The result of an ANCA is either positive or negative cANCA or pANCA or ambiguous.
These are IIF tests requiring a degree of human judgment in determining the reported test levels.
The anti-PR3 and the anti-MPO are related tests using the ELISA or capture ELISA techniques.
The ELISA tests less subject to errors in determining the level of the test results than is the ANCA test.
The latest ELISA is the "sandwich" ELISA.
Major advantages of this technique are that the antigen used to detect the test antigen does not need to be purified prior to use, and that these assay results are very specific.
One disadvantage is that not all antibodies can be used.
Monoclonal antibody combinations must be qualified as “matched pairs”, meaning that they can recognize separate epitopes on the antigen so they do not hinder each other’s binding.
The pANCA IIF test or the anti-MPO test, if positive may an indicator for a small percentage of WG patients.
It is a stronger indicator for some other types of autoimmune diseases e.g. microscopic polyarteritis (MPA), polyarteritis nodosa, etc..
ELISA tests for the anti-Proteinase-3 antibody (anti-PR-3) are somewhat more specific to WG than ANCA, and perhaps more sensitive also.
The anti-PR-3 test may be somewhat more reliable in determining disease activity level than is the cANCA test.
At least one study shows that for diagnosis of WG, both ANCA using IIF and anti-PR-3 using ELISA result in greater sensitivity than either test alone.
This finding is in some disagreement with a single 2003 study which showed that ELISA alone to be sufficient.
Medical consensus seems to be that both the IIF and ELISA tests should be ordered for diagnoses.
The combined result of the ANCA/anti-PR3 tests is 90+% accurate for serious cases of WG, but only about 30% or so for light cases.
The correlation between ANCA test results and WG activity is only about 30%, so it's not dependable in tracking WG activity after diagnosis.
A rise in cANCA/anti-PR-3 sometimes precedes a relapse, but sometimes the rise occurs later.
Not all medical labs do the ANCA and anti-PR3/anti-MPO tests so frequently they are 'send-out' tests to larger labs.
It is possible but unusual to have active WG and be negative in one or both tests (cANCA and anti-PR-3).
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| chemamr
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nice question, i didn't know that. 
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| cyra
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Thanks for posting this AAAA.
A couple of search results I pulled up after coming across this question use the terms PR3 and C-ANCA interchangeably.My question is that are they the same thing...perhaps PR3 is a pattern of C-ANCA that we see(somewhat like the rim/speckled patterns in the anti-DNA antiboides)?If not,how are the two different?
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