Phenotype

• Microscopic Polyangiitis aka MPA
  • No granulomas, no asthma
• Wegener’s Granulomatosis aka GPA
  • Granulomas, no Asthma
• Churg-Strauss Syndrome
  • Eosinophilia (~10%), Asthma, Granulomas

O’Shaughnessy MM et al, JASN 2017, 12:614-623

Serotype

C-ANCA & P-ANCA

The P/C-ANCA are performed by indirect immunofluorescence on ethanol fixed slides – as they represent the pattern of neutrophil staining. They are reported semi-quantitatively as reciprocal of titres 1:40 = 40 , 1:160 = 160, etc

Re SNP/QML: All private labs perform P/C-ANCA using this same protocol but use different brands of ethanol fixed slides, and likely have different levels of experience of distinguishing typical P/C-ANCA patterns form the atypical P/C-ANCA patterns (distinguishing atypical from typical is very important for disease correlation)

• C-ANCA is typically a diffuse fine granular labeling of the cytoplasm that is accentuated between the nuclear lobes
• P-ANCA yields a finely rimmed, homogeneous fluorescence staining of the perinuclear cytoplasm. Labeling of the perinuclear cytoplasm by p-ANCA is actually an artefact of ethanol fixation, which causes a redistribution of the positively charged cytoplasmic granular proteins to collapse onto the surface of the negatively charged nucleus.

Anti-MPO or Anti-PR3

• MPO/PR3-ANCA are measured quantitatively by automated immunoassay OR Luminex/Bead assay OR ELISA – hence the results are reported as arbitrary manufacturer-specific units.

• Enzyme-linked immunosorbent assay (ELISA): will confirm an antigenic target of the ANCA

• Unclear the best diagnostic path – some groups advocate using ELISA exclusively , others feels ELISAS are not yet suitable for screening due to the higher false neg rate (~40% in this study case)

• None of the major lab in QLD use ELISA anymore (I can’t comment for 4cyte pathology or medlabs).

• QML previously used a Luminex/bead assay but now use the same automated immunoassay (PHADIA/FEIA) as SNP

• MN use the BIOflash automated immunoassay, which appears to be more sensitive than the PHADIA/FEIA, and also has a wider dynamic range (up to >700 vs >~300 for phadia), but is prone to more low positive results (hence the comments below regarding caution with its use for diagnosis in the absence of P/C-ANCA positivity)

• The value of combining P/C and MPO/PR3-ANCA results is critical as MPO/PR3-ANCA do occur in many non-AAV conditions, in particular IBD (atypical P and/or atypical C-ANCA, and frequently also PR3-ANCA positive), drug-related ANCA (esp PTU, hydralazine, but also allopurinol – usually MPO-ANCA positive (but sometime BOTH MPO and PR3-ANCA positive ASSOCIATED with atypical P (but can be P-ANCA).

• Many countries now just report MPO/PR3-ANCA and no longer perform P/C-ANCA, hence lose the value of correlation with P/C patterns (which significantly improves the PPV of a positive ANCA result for AAV)

Phenotypes

• C-ANCA are primarily present in sera from patients with Wegener’s granulomatosis and mainly recognize proteinase 3.
• P-ANCA are frequently detected in patients with microscopic polyangiitis and most often react with myeloperoxidase.

False Positives are common

• ANCA in ulcerative colitis (UC; 60–87%), primary sclerosing cholangitis (PSC; 60–92%), autoimmune hepatitis (AIH; 50–96%) and, to a lesser extent, Crohn’s disease (CD; 5–25%)
• No cytoplasmic target yet identified in these GI cases - various proposed names atypical p-ANCA’, ‘a-ANCA’ or ‘x-ANCA’. There is likely a perinuclear target here, so perhaps atypical p-ANCA’, ‘a-ANCA’ or ’perinuclear antineutrophil nuclear antibodies (p-ANNA)

Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5628710/

Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5628710/( adapted)

• Notes:
  • 90% sensitive i.e. 10% of clinical phenotypes will be ANCA negative.
  • Skin biopsies are useless, nonspecific leukocytoclastic.
  • Be alert for overlap with both antiGBM and immune complex disease e.g MN, LN, IGAN – always test for ANCA and antiGBM together
  • Consider the predilection for elderly but don’t miss the rare young ones.
  • Dual positive MPO and PR3 – rare, consider drug induced e.g. Hydralazine.
  • PR3 OR higher in Men, tend to be younger, higher eGFR
  • OR of being PR3 increases from South to North i.e with decreasing UV radiation

Immune complex

• Anti GBM
  • In situ immune complex formation
  • Linear IF staining
  • Highly restricted to small vessels
  • Never causes arteritis – i.e. if you see arteritis in anti GBM disease its probably coexisting ANCA vasculitis.
• IGA Vasculitis
  • Systemic - IgA Dominant vessel wall deposits
  • anti IgA1 may be relevant in future
• Cryoglobulinaemic
  • Cryoglobulins in blood and vessel
  • Hypocomplementic
  • High Rh factors can support
  • Skin, gloms and peripheral nerves classic
• Anti c1q (hypocomplementaemia urticarial vasculitis)
  • Hypocomplementic
  • Circulating anti C1q antibodies
  • GN resembles lupus nephritis
  • GN, uveitis and episcleritis are common

Variable: Cogans, Bechet’s

Single organ: Cutaneous small vessel vasculitis, primary CNS

Systemic disease : Rh, Lupus, Sarcoid

Misc

• HBV – range of presentations – from PAN to Small vessel ANCA like
• Drugs – dual positive classic

Infectious

• Bacterial
• Rickettsial (e.g. Rocky Mountain Spotted Fever – Dog tick, derm vasculitis, If+)
• Viral
• Fungal

ANCA & anti GBM dual positive

• ~5% of all AAV cases are also GBM positive.
• 32% of GBM are ANCA +
• Renal Outcomes and survival more similar to Anti GBM - bad outcomes
• severe AKI typically
• 50% have Alveolar haemorrhage
• 30% of other manifestations e.g. ear, nose ,throat, joints.
• 72% MPO, 20% PR3.
• triple positive very rare - 2.9% of recent case series of dual positives.
• Always check both simultaneously! Dont try to be clever, just do it.

Review: Autoimmun Rev 2021

ANCA in Infective Endocaritis

ANCA positivity does not exclude infection in as cause of AKI in IE

• 18–43% of infective endocarditis (IE) patients are ANCA-positive, most often cytoplasmic ANCA/anti-PR3.
  
• Clinical features, renal involvement, and serology can mimic ANCA-associated vasculitis (AAV).
  
• Maintain suspicion for underlying infection even with positive ANCA, especially if blood cultures are pending or renal function is worsening.

Interesting phenotype in case series - not typical AAV

• 79% Males, 89% consistutional, 64% new murmer(Low! - and only 79% had vegetations, but 89% had an organism)
• differentiation from AAV: 44% splenomegaly, 38% cutaneous
• 38% Cryos, 68% hypocomplementaemia, 72% AKI, 82% haematurioa, 59% thrombocytopaenia.
• TITRES: Median increase was 4.5 times the upper reference limit with 50% of titres falling between 2.6 and 8.5 times the upper reference limit, and 40% of cases having titers below 4 times the upper reference limit

Antibiotics are the therapeutic cornerstone; use immunosuppression cautiously

• All patients received antibiotics; 39% also received immunosuppressants (often due to suspected vasculitis).
  
• Many ANCA-associated symptoms resolved or stabilised with antibiotics alone.
  
• ANCA titres became negative in 69% during follow-up; no persistent AAV developed.

The Almighty Biopsy

• 51% crescentic, 18% proliferative.
• immune complexes in 59%!! while showing pauci-immune glomerulonephritis in 37%.
• does that mean it was all infection related, or could it be superimposed?
• I suggest very cautious approach to immunosupression, usually best to watch-and-wait as long as possible

Review: Clinical Rheumatol. 2022

Induction

Glucocorticoids & Ritux/cylophos

• Cylcophos: RPGN, aggressive disease (pulmonary, neuro), Cr >354

  • CYCLOPS: IV=PO for remission, 50% less exposure, less leukopaenia, more relapse

• Ritux: PR3 (RAVE, OR 2.11 for remission), children, frail older, sparing steroids, fertility concerns, bladder cancer. RAVE excluded severe AKI >350.

• Combo: RITUXIVAS – 375mg/m2 weekly *4, CTX pulse 15mg/kg with ritux#1 nd #3 == 6/12 CTX & AZA

• PEX: MEPEX ( Cr>500 ARR 6%), Consider for Cr >300 (ARR 4.6%), requiring HD, pulmonary haemorrhage, GBM overlap. PEXIVAS didn’t show benefit in eGFR <50 or pul haem (and increased infections), meta-analysis suggests might still be worth it.

  Nonsevere disease only:

• MMF: MYCYC non life threatening, no RPGN, induction=CTX, much higher PR3 relapse.

• MTX: non Renal disease, but high relapse

• AVACOPAN: ADVOCATE – non serious disease as pred alternative. Less SE, maybe a little better for albuminuria. Maybe.

Never forget

• Pre induction check: TB (quantiferon gold), HIV, HBV, HCV, Strongloides
• TMP-SMX for PJP
• IgG levels baseline and 6monthly with ritux.48% will get hypogammaglobulinaemia by 6 months
• Read the CTX protocol ( hold the MMF, fertility, bladder CA risk etc)

Dose

Avacopan

Start within first month, 30mg bd for 12 months, wean pred to zero by 4-6 weeks. Monitor LFTs closely, derangments not uncommon. Note cyp4a interactions (NB azoles). vanishing bile duct reported. Consider staggering the initiation of other hepatotoxic meds such as valgan and cotrim to allow accurate assessment.

Maintanence

Remission: (BVAS=0, stable or improved eGFR, may have persistent urine changes)

Duration: 18 months – 4 years. Options: Ritux vs Aza (MMF) & pred wean

Ritux

• MAINRITSAN (vs aza – less major relapses, not minor) – 500mg*2 at remission, and 500mg at month 6, 12, 18.
• RITZAZREM (relapse, vs aza less major and minor) – 1g post induction, and month 4,8,12,16.
• Can dose as fixed or by CD19 cells ( same relapse rates, lower overall doses)

Aza

• 1.5-2mg/kg/day at remission for 1 year, then drop by 25mg every 3 months.
• 1.5-2mg/kg/day for 18-24 months, then drop 1mg/kg/day for 4 years, then taper 25mg every 3 months. Pred 5-7.5 for 2 years then drop 1mg/2 months.
• AZA-ANCA: 2 vs 4 years – relapse of 48 vs 24%
• MMF if intolerant. ( 1g bd for 2 years)

If still on HD at 3 months – consider discontinuation if no manifestations

PEXIVAS taper ( as effective as high dose, less SE):

Source: KDIGO24

Post remission rising in ANCA

Per Stegeman on the ASN forums:

• In general a significant rise in ANCA titer, either PR3 or MPO, over a period of 3-6 months is associated with a risk of relapse of around 60% in the 6-12 months following the ANCA rise.
• The other 40% will not have a relapse of disease over a period of 1-2 years.
• What a significant rise in ANCA is, is totally dependent on the test used (indirect immune fluorescent tests usually at least a fourfold rise (2 titer steps); ELISA based methods 75-100% increase and 2-3 times the upper limit of normal (so changes in the very low positive range usually mean not much) and should be analyzed for the test you are using to quantify ANCA levels.
• In our experience a continuous slow rise in ANCA (so less than a significant rise in 3-6 months or over a longer period) does not have much prognostic value above the baseline risk of ~10-20% annual risk of relapse associated with persistent positive PR3-ANCA in the first 5 years after diagnosis and initial treatment (for MPO-ANCA the risk seems lower probably more around 5-10%)

So I would advise not to treat an isoloated (significant!) rise in ANCA titer unless you want to minimize the risk of relapse to the absolute minimum (because you fear the consequences of the relapse for the patient, which seems not be the case for this particular patient (given the bothersome but not lifethreatening manifestations of her disease and the fact that most relapses copy the initial presentation and it is unusual (unfortunately not impossible) to have more extensive/severe disease manifestations during relapse as compared to the previous presentations).