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.