Rheumatologic Lab Tests

Transcription

1 Rheumatologic Lab Tests What the Practitioner Needs to Know Mary Nakamura M.D. 2008

2 Rheumatologic Lab Tests Are rarely diagnostic of any specific disease If you do not have in mind a rheumatologic disease before you order it, rarely is it helpful

3 The primary utility of rheumatologic lab tests is within the context of a clinical case to support or refute a clinical impression based on other factors

4 Why are Rheum Tests not diagnostic? What about ANCA? When should I order an ANA? What to do with Positive ANA? Should I use the anti-ccp test?

5 55 yo F in hospital with pneumonia Admitted with LLL pneumonia mild dehydration/nausea from oral Abx Asked to evaluate +canca 1:160 No hx sinusitis/hemoptysis/renal dz No hx medication use now on levofloxacin Doing well about to be D/C to home Labs unremarkable at time of D/C

6 55 yo F +ANCA Hct 37 plt 125 WBC 12 BUN/Cr 30/1.1 U/A neg Lytes, liver function unremarkable CXR LLL infiltrate Sinus films negative The patient is unlikely to have a dx of Wegener s granulomatosis given the low positive predictive value of the test

7 The positive predictive value of the test is low because: A. c-anca specificity is 25% for Wegener s B. c-anca sensitivity is 40% for Wegener s C. Low prevalence of disease D. The negative likelihood ratio is high

8 The positive predictive value of the test is low because: A. C-ANCA specificity is only 25% for Wegener s B. C-ANCA sensitivity is only 40% for Wegener s C. Low prevalence of disease D. The negative likelihood ratio is high

9 Be familiar with how lab tests have been determined to be useful sensitivity, specificity, positive and negative predictive value, positive and negative likelihood ratios

10 ANCA sensitivity ANCA are detectable in nearly all patients with active severe Wegener's granulomatosis 180 pt in multicentric prospective trial multiple ANCA tests IF, ELISA, capture ELISA 166 (92%) ANCA positive 96% with severe disease 83% with limited disease (1 of 5 ANCA negative) Finkielman JD et al Am J Med. 2007, 120:643

11 ELISAs for ANCA PR3 antibody= proteinase 3 antigen Most specific for Wegener s Myeloperoxidase Not generally seen in Wegener s Somewhat associated with other types of vasculitis but far less specific

12 Positive predictive value = how many of the test positive patients truly have the disease = True positive True positives + false positives dependent on the prevalence of the disease in the population being examined (pretest probability of disease)

13 Positive predictive value of canca 1. Wegener s pulm/renal syndrome 3. systemic vasculitis 4. rapidly progressive GN 5 5. Any GN 6. Any reason to be in hospital 6

14 In correct clinical setting, c-anca can be diagnostic but generally biopsy is still needed for diagnosis -remember morbidity of therapy Positive predictive value of ANCA Despite a sensitivity and specificity of 95%, the utility of the test is dependent on the population of patient being evaluated Wegener s is a rare disease

15 ANCAs causative of disease? Neutrophils exposed to inflammatory cytokines show some surface expression of serine proteinase and myeloperoxidase, the targets for ANCAs Adding ANCAs to cytokine-primed neutrophils causes them to generate oxygen radicals and release enzymes capable of damaging blood vessels.

16 ANCA does not track disease activity Prospective multicenter study ANCA levels are only weakly associated with disease activity ANCA levels should not be used to guide clinical therapy Finkielman JD et al 2007Ann Int Med 147:611

17 ANCA associated autoimmune diseases induced by antithyroid drugs: Induced by PTU and methimazole (ATD) two groups: 1) drug-induced WG or MPA which resembles idiopathic vasculitis Renal dz in 18.8% ATD-treated, 75% vasculitis Skin dz in 62.5% ATD-treated, 25% vasculitis 2) drug induced lupus like disease Of 16 ATD-treated pts with autoimmunity 4 ANCA vasculitis (three MPA and one WG) 12 lupus-like disease Arthritis Res Ther 2005, 7:R

18 74 yo M with ANA+ 1:320 Hx Afib On coumadin, amiodarone Hx of procainamide use in past Hx of chronic knee and back pain Labs, PE unremarkable

19 The following are true except: A) ANA is likely due to presence of antihistone antibodies B) His ANA will become negative after he is off procainamide for 2 years C) the patient does not have drug induced lupus D) there is no indication for ordering additional autoantibody tests

20 The following are true except: A) ANA is likely due to presence of antihistone antibodies B) His ANA will become negative after he is off procainamide for 2 years C) the patient does not have drug induced lupus D) there is no indication for ordering additional autoantibody tests

21 ANAs in Normals Healthy controls have positive ANA generally at low titers 1:40, commonly antihistone (homogeneous) Frequency and titers increase with age, particular in women (20-25% of persons >60) First degree relatives of pt with SLE but without disease have higher ANA titers often 1:160 or greater

22 +ANA in elderly 284 nonagenarians 12.3% ANA + compared with 2.8% middle-aged controls mortality data of this cohort collected after a 4-year follow-up. +ANA at age 90 did not have any effect on the rate of survival, or on the levels of serum markers of inflammation.

23 Homogeneous Speckled Anti-histone anti-u1rnp

24 Drug Induced ANAs + ANA are seen in >50% pts on Procainamide, 50% on hydralazine or chorpromazine, 25% on INH or methyldopa Only a small proportion of these pt develop clinical sx of lupus Clinical syndrome of drug induced lupus by definition subsides on discontinuation of the drug

25 Drug Induced ANAs +ANA test however will persist for months to many years after drug is discontinued Anti-histone antibodies are predominant specificity in drug induced lupus

26 ANA appearing before clinical SLE Department of Defense serum repository 130 pts with SLE 115/130 (88%) had +autoantibody test before dx(mean 3.3 yrs max 9.4 yrs) 78% +ANA all types auto ab seen Progression +ANA,antiRo, La, APL Ab antidsdna then antism,rnp Arbuckle et al NEJM 349:

27 ANA appearing before clinical SLE SLE Pts can develop a +ANA years before onset of clinical sx of disease Not all pt with a +ANA do go on to develop clinical sx of an autoimmune disease There is currently no way to distinguish who will or will not go on to SLE There is currently no treatment to prevent disease development

28 ANA Making sense of a +ANA test requires consideration of CLINICAL SETTING Titer Pattern Presence or absence of other autoantibodies

29 Approach to Determining the Cause of a +ANA Clinical status of patient is the most important factor Examine with attention to occult hepatic dz, pulmonary dx, chronic infection Check liver enzymes, CBC, U/A for unrecognized abnormalities Review meds Check family history for CTD

30 Approach to Determining the Cause of a +ANA If sx/hx point to systemic connective tissue dz consider additional autoab tests SLE-anti ds DNA, Sm Sjögrens- anti-ro, La Scleroderma-anti-Scl-70, RA- RF anti-centromere

31 45yo F with 8 yr hx of RA +RF, known erosive dz in hands by xray for past 5 years Maintained on MTX, prednisone, and etodolac until 3 months ago when started on etanercept biweekly, MTX D/C ed Pt had been doing well until the last 2 weeks when she developed a vasculitic rash on her left lower leg (away from injection site)

32 Therapy for this patient should include: A) Increase of prednisone dose B) Initiation of plaquenil for SLE/RA C) Discontinuation of etanercept D) Discontinuation of etodolac

33 Therapy for this patient should include: A) Increase of prednisone dose B) Initiation of plaquenil for SLE/RA C) Discontinuation of etanercept D) Discontinuation of etodolac

34 TNF blockade can induce autoantibodies Seen in RA, Crohn s, Spondyloarthropathy Infliximab: +ANA in ~64% RA and ~49% Crohn s pt +anti ds-dna 13% RA, ~21% Crohns pt Etanercept +ANA in 11%, +anti ds-dna 13% RA pt Clinical SLE rare with either drug

35 Drug Induced LE with TNF blockade sx similar to other drug induced LE: rash, cutaneous vasculitis, serositis, joint pain, fatigue unlike other DLE, anti-histone antibodies not a prominent feature unknown whether preexistance of +ANA or +anti-dsdna poses increased risk of drug induced disease

36 Which of the following is false? A) Presence of anti-ccp Abs correlates with the presence of the shared HLA Class II epitope in RA pts B) Citrulline is a post translational modification of arginine C) CCP3 tests are done by immunofluorescence D) Multiple citrullinated proteins are recognized by anti-citrullinated Abs

37 Which of the following is false? A) Presence of anti-ccp Abs correlates with the presence of the shared HLA Class II epitope in RA pts B) Citrulline is a post translational modification of arginine C) CCP3 tests are done by immunofluorescence D) Multiple citrullinated proteins are recognized by anti-citrullinated Abs

38 What is the deal about (anti-ccp) Anti-citrullinated peptide antibodies? Sensitive (40%-70%) and specific (92%-99%) for diagnosis of RA Old Ab associated with RA: antiperinuclear factor, anti-filaggrin are anti-ccp Abs

39 Anti-CCP Ab Ab presence significantly associated with presence of shared epitope (HLA DR4 haplotypes) and severe erosive disease in RA pts Can be present in early inflammatory arthritis-early marker for RA

40 What is citrullination? posttranslational modification of proteins containing arginine deiminated arginine=citrulline Enzyme responsible is PAD peptidyl arginine deiminase

41 Peptidyl arginine deiminase NH 2 C NH 2 + O C NH 2 NH NH CH 2 PAD CH 2 CH 2 CH 2 Ca ++ CH 2 CH 2 NH CH C NH CH C O O Arginine Citrulline

42 Why should I care about PAD? PAD transcription influenced by estrogenic compounds PAD4 produced in nucleus of granulocytes and monocytes PAD4 polymorphism reported associated with RA in a Japanese study Nature Genetics 34:

43 Could it be important? Anti-CCP antibodies locally produced by plasma cells in synovium?antigen in synovium peptides after citrullination have increased affinity for the MHCII peptide binding groove of HLA DRB allele suggests interaction between citrullinated peptides and the shared epitope could alter T cell activation May be induced by smoking a known risk factor for RA

44 Is anti-ccp really specific? Seen in HLA DR4+ pt with polyarticular onset JRA (RF+) Seen in Psoriatic Arthritis pt with HLA DRB1 shared epitope In both sets of pts correlated with erosive disease Rarely seen in SLE or Sjögren s

45 Anti-CCP Ab NOT found in PMR HCV associated arthropathy

46 CCP Ab Metaanalysis 37 studies re CCP 50 studies re RF Pooled sensitivity 67%, specificity 95%, positive likelihood ratio 12.46, negative likelihood ratio 0.36 Risk of radiographic progression greater with +anti-ccp than +RF More specific than RF and may be better predictor of erosive disease Nishimura K, et al Ann Intern Med. 2007;146:

47 Summary: Anti-citrullinated peptide antibodies compelling correlations with RA, genetic risks and disease severity standardized testing now available Better correlated with diagnosis of RA than RF particularly in early disease may be better predictor of disease severity than RF, particularly in RF negative patients

48 Anti-CCP Supportive of a diagnosis of RA Like presence of +RF in an RA pt, may be predictor of more severe disease Particularly useful in evaluation of the suspected RA pt with a negative RF Useful in Hepatitis C patient with RA like symptoms

49 Good Rules Don t order a rheumatologic lab test unless you have a specific rheumatologic disease in mind Rheumatologic Tests are useful to support your clinical diagnosis but are unlikely to make your diagnosis for you