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Autoantibody Profiles: SLE, RA, Vasculitis — MRCP Part 1

TL;DR:

Autoantibody questions are high-yield and predictable in MRCP Part 1. Examiners repeatedly test recognition of disease-specific antibodies, their prognostic value, and classic pitfalls. This article distils the key autoantibody profiles in systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and vasculitis, with an exam-style case and a practical revision checklist.


Why this topic matters for MRCP Part 1

Autoantibodies bridge immunology, rheumatology, nephrology, and respiratory medicine—core MRCP territory. Unlike vague symptom questions, these are pattern-recognition marks. If you can match antibody → disease → organ involvement, you score quickly.

Authoritative guidance on MRCP content and exam structure is published by the MRCP(UK) diploma board:https://www.mrcpuk.org/


Scope: what the exam actually tests

MRCP Part 1 focuses on:

  1. Disease-defining antibodies

  2. Antibodies predicting severity or organ involvement

  3. Differentiation between similar conditions

  4. Common false assumptions (deliberate traps)

You are not expected to memorise rare research antibodies.


High-yield autoantibody profiles (exam table)

Condition

Key autoantibodies

What examiners want you to know

SLE

ANA, anti-dsDNA, anti-Smith

dsDNA correlates with disease activity; anti-Smith is highly specific

Antiphospholipid syndrome

Lupus anticoagulant, anticardiolipin

Thrombosis + prolonged APTT paradox

Rheumatoid arthritis

RF, anti-CCP

Anti-CCP predicts severe, erosive disease

Granulomatosis with polyangiitis (GPA)

c-ANCA (PR3)

ENT + lung + kidney involvement

Microscopic polyangiitis (MPA)

p-ANCA (MPO)

Pulmonary-renal syndrome

Eosinophilic granulomatosis with polyangiitis (EGPA)

p-ANCA (±)

Asthma + eosinophilia

Exam pearl: Anti-dsDNA levels rise during SLE flares, especially with lupus nephritis.

The 5 most tested subtopics

1) ANA ≠ lupus

  • ANA is sensitive, not specific

  • Up to 20% of healthy people may have low-titre ANA

  • Diagnosis requires clinical features + specific antibodies

2) Anti-dsDNA and renal disease in SLE

  • Strong association with lupus nephritis

  • Levels correlate with disease activity

  • Often tested alongside low complement (C3, C4)

3) Anti-CCP vs rheumatoid factor

  • RF: sensitive, but non-specific (seen in infections, elderly)

  • Anti-CCP: highly specific and prognostic

4) ANCA patterns matter

  • c-ANCA (PR3) → GPA

  • p-ANCA (MPO) → MPA

Trap: Assuming p-ANCA always equals EGPA.

5) Antiphospholipid antibodies cause clotting

  • Lupus anticoagulant prolongs APTT in vitro

  • Causes thrombosis in vivo


MRCP Part 1 candidate revising autoantibodies in immunology and rheumatology

Mini-case (MRCP style)

A 30-year-old woman presents with photosensitive rash, arthralgia, and new-onset proteinuria. Blood tests show low C3 and C4.

Which antibody is most likely to rise during disease flare?

A. Anti-SmithB. ANAC. Anti-dsDNAD. Anti-CCPE. Rheumatoid factor

Correct answer: C — Anti-dsDNA

Explanation: Anti-dsDNA correlates with disease activity and lupus nephritis. ANA is useful for screening, not monitoring.


Common pitfalls (examiner favourites)

  • Treating ANA positivity as diagnostic of SLE

  • Confusing RF specificity with anti-CCP

  • Forgetting dsDNA tracks lupus activity

  • Mixing up p-ANCA–associated diseases

  • Missing antiphospholipid syndrome in young stroke patients


Practical study-tip checklist

  • ☐ Learn one antibody per disease first, then layer details

  • ☐ Link antibodies to organ systems (kidney, lung, joints)

  • ☐ Practise with vignettes, not isolated facts

  • ☐ Re-test tables every 7 days (spaced repetition)

  • ☐ Use NICE and MRCP(UK)-aligned sources only


FAQs

Is ANA always positive in SLE?

No. ANA is highly sensitive but not universal, and it lacks specificity.

Which antibody predicts severe rheumatoid arthritis?

Anti-CCP is most predictive of aggressive, erosive disease.

Does p-ANCA always mean vasculitis?

No. p-ANCA can be seen in inflammatory bowel disease and other conditions.

Which antibody best tracks lupus activity?

Anti-dsDNA correlates best with disease flares and nephritis.


Ready to start?

Ready to turn autoantibody recognition into guaranteed MRCP Part 1 marks?

👉 Practise exam-level questions now with the Crack Medicine MRCP QBank:https://crackmedicine.com/qbank/

👉 Test yourself under real exam conditions using full-length mock tests:https://crackmedicine.com/mock-tests/

👉 Reinforce concepts fast with clinician-led MRCP video lectures:https://crackmedicine.com/lectures/


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