Anti-Neutrophil Cytoplasmic Antibodies(ANCA)
Ted BrownCP Case ConferenceFebruary 24, 2012
ANCA
Antibodies against neutrophil cytoplasmic antigens
Most common targeted antigens are myeloperoxidase (MPO) and proteinase 3 (PR3)
Prevalent among adults in 50s and 60s, M=F
We perform 2 assays:
1.Indirect immunofluorescence assay: normal human neutrophils (sensitive)2.Enzyme-linked immunosorbent assay: specific antigen (specific)
When is ANCA testing ordered?
Clinical suspicion of systemic autoimmune vasculitis
Symptoms nonspecific in early disease (fever, fatigue, aches) to more diffuse in later disease (proteinuria, cough, rash/granuloma, runny nose, peripheral neuropathy, pulmonary hemorrhage and hemoptysis)
Integrate clinical and laboratory info
ANCA, ANA, complement, cryoglobulins, hepatitis B and C, rheumatoid factor, azotemia, hematuria, proteinuria, recent drug history
Indirect Immunofluorescence
Patient sera on ethanol fixed PMNs
Indirect Immunofluorescence
Patient sera on ethanol fixed PMNs
Indirect Immunofluorescence
Patient sera on formalin fixed PMNs
ELISA
If indirect immunofluorescence microscopy positive, perform ELISA
Determine amount of antibody present: Titer determined by serial dilutions
PR3 and MPO antibodies
Diseases with ANCA
C-ANCA and PR3: Wegener’s (90% in active, generalized granulomatous and polyangiitis disease; 60-70% in no active disease)
P-ANCA and MPO: Microscopic polyangitis (70%), Churg –Strauss (50%), drugs
ANCA-positivity also seen in other diseases, including gastrointestinal disorders
•60-80% with ulcerative colitis and related disorder primary sclerosing cholangitis
•<30% in Chron’s disease
Patient Case
48 year old female with known leukocytoclastic vasculitis and ulcerative colitis
Recent use of cocaine
Increased arthralgias
No history of ANCA testing
Cocaine and ANCA vasculitis
~70% of cocaine bought illicitly in US contaminated with levamisole
Levamisole-contaiminated cocaine associated with ANCA vasculitis
Clinical symptoms: arthralgias, skin lesions, fever.
Clinical Applications of ANCA testing
Positive test really a true positive?
+ Immunofluorescence and ELISA= PPV increased to 88%
Negative test a true negative?
Clinical presentation key
Need for a tissue biopsy?
Controversial: reasonable attempts should be made to obtain histologic proof due to long-term treatment commitment with toxic medications.
Use of titers?
Do not use as sole parameter to guide therapy.