Appropriate Serologic Testing Appropriate Serologic Testing

to Evaluate Rheumatic to Evaluate Rheumatic

ComplaintsComplaints

Kathleen M Thomas DOKathleen M Thomas DOCommunity RheumatologyCommunity Rheumatology

Community Physician NetworkCommunity Physician Network

Noblesville, IndianaNoblesville, Indiana

April 26, 2012April 26, 2012

Objectives Objectives

�� Describe lab tests most useful in the Describe lab tests most useful in the evaluation of common rheumatic diseasesevaluation of common rheumatic diseases

�� Recognize the serologic associations of Recognize the serologic associations of rheumatic diseasesrheumatic diseases

�� Apply sensitivity, specificity, likelihood Apply sensitivity, specificity, likelihood ratio (LR) and positive predictive value to ratio (LR) and positive predictive value to laboratory testing in clinical practicelaboratory testing in clinical practice

Case study #1Case study #1

�� 28 28 yy--oo female with 6 months of female with 6 months of HAsHAs, , fatigue and fatigue and arthralgiasarthralgias. She hurts all . She hurts all day, Advil, Tylenol provide no relief. day, Advil, Tylenol provide no relief. Occasional oral ulcers around Occasional oral ulcers around menses. Going through divorce and menses. Going through divorce and worried about her kidsworried about her kids

��On exam muscle and joints, including On exam muscle and joints, including hands and feet, are tender, she is hands and feet, are tender, she is weepyweepy

Case study #1Case study #1

�� What do you suspect?What do you suspect?–– LupusLupus

–– RARA

–– FibromyalgiaFibromyalgia

–– Depression/anxietyDepression/anxiety

�� What would you order?What would you order?–– ANA, RF, ESR, uric acidANA, RF, ESR, uric acid

–– Sleep studySleep study

–– Vitamin D, TSH, hepatitis panel, CKVitamin D, TSH, hepatitis panel, CK

Objective 1Objective 1

��Describe lab tests most useful in the Describe lab tests most useful in the

evaluation of common rheumatic evaluation of common rheumatic

diseasesdiseases

Initial Approach When Faced with Diffuse Initial Approach When Faced with Diffuse

Rheumatic Disease PresentationRheumatic Disease Presentation

�� Is it arthritis (in the joints) or not Is it arthritis (in the joints) or not (bursitis, fibromyalgia, etc)(bursitis, fibromyalgia, etc)–– Answer by H&PAnswer by H&P

�� Is it inflammatory or not?Is it inflammatory or not?–– Answer by H&PAnswer by H&P

–– Labs: ESR, CRP, CBCLabs: ESR, CRP, CBC

�� If arthritis, is it one of the common If arthritis, is it one of the common inflammatory conditions?inflammatory conditions?–– Answer by H&PAnswer by H&P

–– Labs: RF, CCP, ANA panelLabs: RF, CCP, ANA panel

Diagnostic Laboratory Evaluation of Diagnostic Laboratory Evaluation of

Possible Inflammatory ArthritisPossible Inflammatory Arthritis

�� Inflammatory markersInflammatory markers

–– ESR and/or CRPESR and/or CRP

�� For diagnosis/prognosis: RF and CCPFor diagnosis/prognosis: RF and CCP

��Consider ANA panelConsider ANA panel

–– Patients may be Patients may be seronegativeseronegative early in early in

disease, and even have normal disease, and even have normal

ESR/CRP, but a +ANA may heighten ESR/CRP, but a +ANA may heighten

suspicionsuspicion

Rheumatoid FactorRheumatoid Factor

�� RF is an autoantibody directed against RF is an autoantibody directed against IgGIgG

Rheumatoid FactorRheumatoid Factor

�� Present in 70Present in 70--80% of RA patients 80% of RA patients vsvs

about 5% of normal populationabout 5% of normal population

��Also present in other rheumatic Also present in other rheumatic

diseases and chronic diseasediseases and chronic disease

�� Prognostic value: Prognostic value: high levels high levels

associated with more severe joint associated with more severe joint

disease and extradisease and extra--articulararticular diseasedisease

Rheumatoid FactorRheumatoid Factor

�� Assists in diagnosisAssists in diagnosis

–– In a patient with suggestive findings In a patient with suggestive findings

(symmetric (symmetric polyarthritispolyarthritis), presence increases ), presence increases

the certainty of diagnosis, if other causes the certainty of diagnosis, if other causes

excludedexcluded

�� Assists in prognosisAssists in prognosis

–– High titer increases the progression to erosive High titer increases the progression to erosive

arthritisarthritis

�� Assists in treatment decisionsAssists in treatment decisions

–– Warrants early DMARD useWarrants early DMARD use

Clinical associations of RFClinical associations of RF

�� Rheumatoid arthritis (75Rheumatoid arthritis (75--80%)80%)

�� Other rheumatic diseaseOther rheumatic disease–– SjogrenSjogren’’ss syndrome (~90%)syndrome (~90%)

–– SLE (15SLE (15--20%)20%)

–– SarcoidosisSarcoidosis (~15%)(~15%)

–– Parvovirus Parvovirus arthropathyarthropathy (~15%, transient)(~15%, transient)

–– Mixed Mixed cryoglobulinemiacryoglobulinemia (95%)(95%)

�� Chronic infectionsChronic infections–– Chronic Chronic HepHep CC

–– OsteomyelitisOsteomyelitis

–– Bacterial Bacterial endocarditisendocarditis

�� Monoclonal Monoclonal IgMIgM paraproteinsparaproteins

�� Normal aging (present at low titer)Normal aging (present at low titer)

Frequency of +RF in Normal PopulationFrequency of +RF in Normal Population

by Ageby Age

1010--25%25%>70 yrs>70 yrs

5%5%6060--70 yrs70 yrs

22--4%4%2020--60 yrs60 yrs

Frequency of Frequency of

+RF+RF

AGEAGE

RF as RF as ““screeningscreening””

�� RARA–– Prevalence of RA ~1.2% in USPrevalence of RA ~1.2% in US

–– +RF 80%+RF 80%

�� HCVHCV–– Prevalence ~1Prevalence ~1--2% in US2% in US

–– RF+ rate 40RF+ rate 40--70%70%

�� Given positive RF in US population, risk of Given positive RF in US population, risk of HCV about the same as RAHCV about the same as RA

�� Consider HCV arthritis in RF+ patient with Consider HCV arthritis in RF+ patient with nonnon--erosive disease or erosive disease or arthralgiasarthralgias

Cyclic Cyclic CitrullinatedCitrullinated Peptide Peptide

antibodyantibody

��Also called Also called ACPAsACPAs

��CitrullinationCitrullination is a postis a post--translational translational

modification of modification of argininearginine

�� Peptides after Peptides after citrullinationcitrullination have have

increased affinity for MHCII binding increased affinity for MHCII binding

groove of HLA DRB1 0401 allelegroove of HLA DRB1 0401 allele

��AntiAnti--CCP antibodies locally produced CCP antibodies locally produced

by plasma cells in by plasma cells in synoviumsynovium

Cyclic Cyclic CitrullinatedCitrullinated Peptide antibodyPeptide antibody

��Similar sensitivity as RF, Similar sensitivity as RF, greatergreater

specificityspecificity

–– Less common with Less common with SjogrensSjogrens or SLEor SLE

––Not seen in HCV or other chronic Not seen in HCV or other chronic

infections or PMRinfections or PMR

��Often present Often present earlyearly, and predictive of , and predictive of

severe, erosive diseasesevere, erosive disease

��Can be discordant with RFCan be discordant with RF

RF and CCPRF and CCP

78%78%74%74%RFRF

97%97%77%77%AntiAnti--CCPCCP

SpecificitySpecificitySensitivitySensitivity

2010 Classification Criteria2010 Classification Criteria

�� More emphasis on clinical presentation, shift More emphasis on clinical presentation, shift

away from older criteria like nodules and away from older criteria like nodules and

radiographic damageradiographic damage

2010 ACR/EULAR

Classification Criteria for RAJOINT DISTRIBUTION (0JOINT DISTRIBUTION (0--5)5)

1 large joint1 large joint 00

22--10 large joints 10 large joints 11

11--3 small joints (large joints not counted)3 small joints (large joints not counted) 22

44--10 small joints (large joints not counted)10 small joints (large joints not counted) 33

>10 joints (at least one small joint)>10 joints (at least one small joint) 55

SEROLOGY (0SEROLOGY (0--3)3)

Negative RF Negative RF ANDAND negative ACPAnegative ACPA 00

Low positive RF Low positive RF OROR low positive ACPAlow positive ACPA 22

High positive RF High positive RF OROR high positive ACPAhigh positive ACPA 33

SYMPTOM DURATION (0SYMPTOM DURATION (0--1)1)

<6 weeks<6 weeks 00

≥≥6 weeks6 weeks 11

ACUTE PHASE REACTANTS (0ACUTE PHASE REACTANTS (0--1)1)

Normal CRP Normal CRP ANDAND normal ESRnormal ESR 00

Abnormal CRP Abnormal CRP OROR abnormal ESRabnormal ESR 11

≥6 = definite RA

What if the score is <6?

Patient might fulfill the criteria…

� Prospectively over time

(cumulatively)

���� Retrospectively if data on all

four domains have been

adequately recorded in the past

Acute Phase ProteinsAcute Phase Proteins

�� Proteins whose plasma Proteins whose plasma concentrations change by at least concentrations change by at least 25% during inflammatory states25% during inflammatory states

�� Those that increase are called Those that increase are called positive phase reactants, e.g. CRP, positive phase reactants, e.g. CRP, haptoglobinhaptoglobin, , ferritinferritin

��Negative reactants decrease with Negative reactants decrease with inflammation, e.g. albumin, inflammation, e.g. albumin, transferrintransferrin

Acute Phase ReactantsAcute Phase Reactants

�� Lack specificity, but can be useful in Lack specificity, but can be useful in

reflecting the presence and intensity reflecting the presence and intensity

of inflammatory processof inflammatory process

��Most commonly used ESR and CRPMost commonly used ESR and CRP

Case # 2Case # 2

�� 76 76 yoyo female awoke with stiffness in her female awoke with stiffness in her neck and shoulders, trouble climbing out neck and shoulders, trouble climbing out of bed; persisted for weeksof bed; persisted for weeks

�� Fatigue, anorexia, pain awakens her at Fatigue, anorexia, pain awakens her at night, feels weak, no swollen joints or night, feels weak, no swollen joints or vision changesvision changes

�� One exam, normal temporal arteries, no One exam, normal temporal arteries, no scalp tenderness. She moves slowly, scalp tenderness. She moves slowly, temp 100.1, givetemp 100.1, give--way weakness of way weakness of proximal muscles due to painproximal muscles due to pain

�� ESR 92 = ESR 92 = PMRPMR

ESRESR

��A measure of the distance in A measure of the distance in millimeters that millimeters that RBCsRBCs fall in a tube fall in a tube over an hourover an hour

��An An indirectindirect measurement of measurement of alterations in acutealterations in acute--phase reactantsphase reactants

��Results can be affected by anemiaResults can be affected by anemia

��Changes slowly with change in Changes slowly with change in conditioncondition

��Normal values higher for womenNormal values higher for women

ESRESR

��Markedly elevated (>100mm/hr)Markedly elevated (>100mm/hr)–– InfectionInfection

––MalignancyMalignancy

–– VasculitisVasculitis (CTD(CTD--related, GCA)related, GCA)

��Markedly lowMarkedly low–– AfibrinogenemiaAfibrinogenemia

–– AgammaglobulinemiaAgammaglobulinemia

–– Extreme Extreme polycythemiapolycythemia ((HctHct>65%)>65%)

–– Increased plasma Increased plasma vicosityvicosity

ESRESR

�� It has been suggested that patients It has been suggested that patients

with PMR presenting with lower ESR with PMR presenting with lower ESR

may require lower doses of steroids may require lower doses of steroids

and shorter duration of treatmentand shorter duration of treatment

�� Patients with GCA and lower ESR at Patients with GCA and lower ESR at

higher risk for visual complicationshigher risk for visual complications

CRPCRP

��AcuteAcute--phase reactant produced in phase reactant produced in

response to ILresponse to IL--6 and other cytokines6 and other cytokines

�� Elevation occurs within 4 hours of Elevation occurs within 4 hours of

injury and peaks in 24injury and peaks in 24--72 hours72 hours

��Able to activate the classic Able to activate the classic

complement cascadecomplement cascade

ESR ESR vsvs CRPCRP

�� CRPCRP

–– Better correlates with RA and Better correlates with RA and seronegativeseronegative

spondyloarthritisspondyloarthritis disease activitydisease activity

�� ESRESR

–– Better correlates with SLE activityBetter correlates with SLE activity

�� Discrepancies found with some frequencyDiscrepancies found with some frequency

–– Probably due to differences in production of Probably due to differences in production of

specific cytokines or their modulators in specific cytokines or their modulators in

different diseasesdifferent diseases

ESR and CRPESR and CRP

�� Measurement of any acute phase reactant Measurement of any acute phase reactant

must take into account how the results must take into account how the results

will affect management will affect management

–– H&P generally more reliable reflection of H&P generally more reliable reflection of

disease activitydisease activity

�� Knowing which acute phase reactant Knowing which acute phase reactant

historically correlates with the patienthistorically correlates with the patient’’s s

disease helps chose which to follow over disease helps chose which to follow over

timetime

Case # 3Case # 3

�� 57 y o with acute 57 y o with acute

onset of toe and onset of toe and

ankle painankle pain

�� HTN, DM IIHTN, DM II

�� No traumaNo trauma

�� Low grade feverLow grade fever

�� What do you What do you

order?order?

Mono/Mono/pauciarthritispauciarthritis

�� The Eye of the NeedleThe Eye of the Needle–– Rule out Rule out infection,trauma,hemarthrosisinfection,trauma,hemarthrosis

–– Confirm crystalsConfirm crystals�� MSU MSU –– goutgout

�� CPPD CPPD –– pseudogoutpseudogout

�� Apatite Apatite –– pseudogoutpseudogout, crystals not , crystals not birefringentbirefringent, not , not seen on polarizing microscopeseen on polarizing microscope

�� LabsLabs–– Uric acidUric acid

–– Inflammatory markersInflammatory markers

–– Coagulation panelCoagulation panel

Serum uric acidSerum uric acid

��Males postMales post--puberty mean puberty mean urateurate 5.25.2

––ULN ~ 7mg/dlULN ~ 7mg/dl

––Men with Men with sUAsUA>9.0, 22% develop gout >9.0, 22% develop gout

after 5 yearsafter 5 years

�� PrePre--menopausal women mean 4.0menopausal women mean 4.0

–– Estrogens have a Estrogens have a uricosuricuricosuric effecteffect

�� PostPost--menopausal mean 4.7menopausal mean 4.7

––ULN ~ 6mg/dlULN ~ 6mg/dl

Uric acidUric acid

�� Do not treat asymptomatic Do not treat asymptomatic hyperuricemiahyperuricemia–– 43 million have 43 million have hyperuricemiahyperuricemia, 8 million with gout, 8 million with gout

�� During gout flare, During gout flare, urateurate can be high, normal or can be high, normal or lowlow–– Best time to check baseline is 2 weeks after flare has Best time to check baseline is 2 weeks after flare has resolvedresolved

�� 90% gout patients are 90% gout patients are underexcretorsunderexcretors–– 24 hour urine for 24 hour urine for urateurate and Cr excretion on regular and Cr excretion on regular purinepurine dietdiet

–– UrateUrate >800mg, overproducer; <800mg is >800mg, overproducer; <800mg is underexcretorunderexcretor

–– Spot urine Spot urine urateurate not nearly as accuratenot nearly as accurate

What if crystal exam is negative?What if crystal exam is negative?

��Repeat synovial fluid analysis Repeat synovial fluid analysis

improves sensitivityimproves sensitivity

�� EULAR does allow for presumptive EULAR does allow for presumptive

diagnosisdiagnosis

Case # 4Case # 4

�� 52 y o female 52 y o female

complains of complains of

fatigue, trouble fatigue, trouble

climbing stairs, climbing stairs,

getting dressed but getting dressed but

no painno pain

�� Rash noted on Rash noted on

exam, strength 4/5 exam, strength 4/5

proximal musclesproximal muscles

Idiopathic Inflammatory Idiopathic Inflammatory MyopathiesMyopathiesPolymyositis/DermatomyositisPolymyositis/Dermatomyositis

�� Nonspecific abnormalitiesNonspecific abnormalities

–– CK, CK, aldolasealdolase, AST, ALT, ESR, LDH, AST, ALT, ESR, LDH

–– Elevations of CK can be due to macroElevations of CK can be due to macro--CKCK

�� MyositisMyositis--associated and associated and myositismyositis--specific specific

autoantibodiesautoantibodies

�� Mimics/Mimics/DDxDDx

–– TSH, serum and urine TSH, serum and urine myoglobinmyoglobin, , VitVit D, drug D, drug

screen, HIVscreen, HIV

–– In In myositismyositis vsvs rhabdomyolysisrhabdomyolysis, CK rarely , CK rarely

above 50 x ULNabove 50 x ULN

MyositisMyositis--associated absassociated abs

��ANA (50ANA (50--80%)80%)

��AntiAnti--RNP RNP abab (MCTD/OCTD)(MCTD/OCTD)

��AntiAnti--PMPM--SclScl abab (PM(PM--scleroderma)scleroderma)

��AntiAnti--Ku Ku abab (PM(PM--scleroderma)scleroderma)

MyositisMyositis--specific absspecific abs

ClassicClassic

DMDM

55--10%10%AntiAnti--MiMi--22

Severe Severe

ResistantResistant

PMPM

<5%<5%AntiAnti--SRPSRP

AntisynthetaseAntisynthetase

SyndromeSyndrome

2020--50%50%AntisynthetaseAntisynthetase

e.g. antie.g. anti--JoJo--11

Clinical Clinical

AssociationAssociation

Prevalence Prevalence

DM/PMDM/PM

Autoantibody Autoantibody

Objective #2Objective #2

��Recognize the serologic associations Recognize the serologic associations

of rheumatic diseasesof rheumatic diseases

Case # 5Case # 5

�� 34 34 yy--oo presents presents

with rash after with rash after

cruise to Caribbeancruise to Caribbean

�� AcheyAchey joints, low joints, low

grade fevers, grade fevers,

fatigue, weight lossfatigue, weight loss

�� What do you What do you

order?order?

ANAANA

��ANA panelANA panel

��ANA 95ANA 95--100% sensitive in SLE, but 100% sensitive in SLE, but

far less specificfar less specific

��AutoantibodiesAutoantibodies are hallmark of SLE: are hallmark of SLE:

some diagnostic criteria, some useful some diagnostic criteria, some useful

for prognosis/markers of disease for prognosis/markers of disease

activityactivity

ANAANA

�� Presence of a high titer (>1:640) Presence of a high titer (>1:640) increases suspicion of an autoimmune increases suspicion of an autoimmune disease, but is not diagnosticdisease, but is not diagnostic

�� Titers can fluctuateTiters can fluctuate–– This is not reflective of disease activity, and it This is not reflective of disease activity, and it

is not indicated to follow seriallyis not indicated to follow serially

–– Titers that disappear are less clinically Titers that disappear are less clinically significantsignificant

�� Low titers common in general population Low titers common in general population and in firstand in first--degree relatives of patients degree relatives of patients with ANAwith ANA--associated rheumatic diseaseassociated rheumatic disease

Sensitivity of ANA in Rheumatic Sensitivity of ANA in Rheumatic

DiseasesDiseases

��SLE (95SLE (95--100%)100%)

��Scleroderma (60Scleroderma (60--80%)80%)

��MCTD (100%)MCTD (100%)

��RA (50%)RA (50%)

��SjogrenSjogren’’ss (40(40--70%)70%)

��Discoid lupus (15%)Discoid lupus (15%)

��DrugDrug--induced lupus (100%)induced lupus (100%)

NonNon--rheumatic diseases rheumatic diseases

associated with +ANAassociated with +ANA

��HashimotoHashimoto’’s s thyroiditisthyroiditis (46% (46%

sensitivity)sensitivity)

��GravesGraves’’ disease (50%)disease (50%)

��Autoimmune hepatitis (100%)Autoimmune hepatitis (100%)

�� Primary autoimmune Primary autoimmune cholangitischolangitis

(100%)(100%)

�� Primary pulmonary hypertension Primary pulmonary hypertension

(40%)(40%)

SLE and Autoantibody SubsetsSLE and Autoantibody Subsets

ENA 1ENA 1

��SmithSmith

–– A diagnostic criteria and highly specificA diagnostic criteria and highly specific

–– Sensitivity 20Sensitivity 20--30%30%

��RNPRNP

––Defining feature of MCTDDefining feature of MCTD

Autoantibody SubsetsAutoantibody Subsets

ENA 2ENA 2�� Ro/SSARo/SSA

–– Part of diagnostic criteria for Part of diagnostic criteria for SjogrenSjogren’’ss

�� High titer associated with High titer associated with extraglandularextraglandular featuresfeatures

–– ANAANA--negative SLEnegative SLE

–– Neonatal lupus and CHBNeonatal lupus and CHB

�� Mother antiMother anti--Ro+, risk of fetus with CHB 2Ro+, risk of fetus with CHB 2--5%5%

–– SubacuteSubacute cutaneouscutaneous lupus, lupus, cutaneouscutaneous vasculitisvasculitis, ILD and , ILD and photosensitive dermatitis (normal population)photosensitive dermatitis (normal population)

�� La/SSBLa/SSB–– Part of diagnostic criteria for Part of diagnostic criteria for SjogrenSjogren’’ss

–– 15% of SLE patients but rare in other systemic 15% of SLE patients but rare in other systemic rheumatic diseasesrheumatic diseases

–– Isolated SSB seen in some patients with PBC and AIHIsolated SSB seen in some patients with PBC and AIH

SLE and Autoantibody SubsetsSLE and Autoantibody Subsets

�� dsDNAdsDNA

–– A diagnostic criteriaA diagnostic criteria

––Highly specific ~95%Highly specific ~95%

��Sensitivity ~80%Sensitivity ~80%

––Marker of disease activity (renal) Marker of disease activity (renal)

especially with low complement; especially with low complement;

elevations often precede flares elevations often precede flares

AutoantibodiesAutoantibodies in Systemic in Systemic

LupusLupus

�� Department of Department of Defense Serum Defense Serum Repository; Repository; evaluated 130 evaluated 130 controls prior to controls prior to SLE diagnosisSLE diagnosis

�� 115/130 115/130 (88%)present (88%)present before diagnosis before diagnosis (up to 9.4 years, (up to 9.4 years, mean 3.3)mean 3.3)

�� ANA 78%ANA 78%

�� dsDNAdsDNA 55%55%

�� Progression of Progression of

development:development:

–– ANA, Ro/La, APL absANA, Ro/La, APL abs

–– Later Later dsDNAdsDNA then then

SmSm/RNP/RNP

Arbuckle, et al. (2003). Development of autoantibodies before the clinical onset of systemic lupus erythematousus. NEJM, 34 1526-1533.

AntiAnti--CentromereCentromere antibody (ACA)antibody (ACA)

��Highly specific for scleroderma ~98%Highly specific for scleroderma ~98%

�� Found almost exclusively in limited Found almost exclusively in limited systemic sclerosis (CREST) (57%)systemic sclerosis (CREST) (57%)––CCalcinosisalcinosis

––RRaynaudsaynauds

––EEsophageal sophageal dysmotilitydysmotility

––SSclerodatylyclerodatyly

––TTelangiectasiaselangiectasias

AntiAnti--SCLSCL--70 antibodies70 antibodies

(topoisomerase(topoisomerase--1)1)

��Highly specific for scleroderma ~95%Highly specific for scleroderma ~95%

�� Tightly affiliated with diffuse Tightly affiliated with diffuse

systemic sclerosissystemic sclerosis

–– Associated with high risk of ILDAssociated with high risk of ILD

AntiAnti--histonehistone antibodiesantibodies

�� Present in 95% of DIL (drugPresent in 95% of DIL (drug--induced induced

lupus) patientslupus) patients

�� ProcainamideProcainamide, , HydralazineHydralazine, , IsoniazidIsoniazid

��Also present in up to 80% of SLE ptsAlso present in up to 80% of SLE pts

Positive ANAPositive ANA

High probability of autoimmunerheumatic disease

Identify specificantigen

Search forevidence of other disease or organinvolvement

Ancillary tests e.g.Complement,

Coombs

Positive ANAPositive ANA

Low probabilityof autoimmune

rheumatic disease

Low titer or transient titer:Reassure patient

High titer orpersistent titer:

Search foralternative dx

High titer or persistent titer:Follow patient

ANAANA

��A hallmark of rheumatic diseaseA hallmark of rheumatic disease

�� For diagnosis of SLE, sensitivity of For diagnosis of SLE, sensitivity of

~95% and specificity of 57%~95% and specificity of 57%

�� Primary utility diagnostically is the Primary utility diagnostically is the

NPV for SLE if ANA is negativeNPV for SLE if ANA is negative

��May support the diagnosis of other May support the diagnosis of other

rheumatic disease but does not rule rheumatic disease but does not rule

in or out other specific diseasesin or out other specific diseases

Case # 6Case # 6

�� 60 60 yoyo male hospitalized with male hospitalized with

pneumonia,dehydrationpneumonia,dehydration/nausea from /nausea from

oral antibioticsoral antibiotics

��Cr 1.1 Cr 1.1 HbHb 12 12 pltplt 120 WBC 12 120 WBC 12

cANCAcANCA 1:1601:160

��Does this patient have Does this patient have

GranulomatosisGranulomatosis with with PolyangiiitisPolyangiiitis

((WegenersWegeners)?)?

AntiAnti--NeutrophilNeutrophil CytoplasmicCytoplasmic

Antibody (ANCA)Antibody (ANCA)�� Two patterns:Two patterns:

–– cc--ANCA = diffuse granular staining throughout ANCA = diffuse granular staining throughout cytoplasmcytoplasm�� Antigen recognized is usually a PMN granule Antigen recognized is usually a PMN granule constituent proteinaseconstituent proteinase--3 (Pr3 (Pr--3)3)

�� Found primarily in Found primarily in GranulomatosisGranulomatosis with with PolyangiitisPolyangiitis((WegenersWegeners))

–– pp--ANCA = ANCA = perinuclearperinuclear staining of cytoplasmstaining of cytoplasm�� Many antigens (Many antigens (elastaseelastase, , lysozymelysozyme, , lactoferrinlactoferrin) ) but but

most common and important is PMN granule most common and important is PMN granule constitutentconstitutent myeloperoxidasemyeloperoxidase (MPO)(MPO)

�� NonNon--MPO MPO pANCAspANCAs seen with nonseen with non--rheumatic diseases rheumatic diseases (IBD, HIV, drug(IBD, HIV, drug--induced ANCA e.g.); recognized as induced ANCA e.g.); recognized as atypical atypical ANCAsANCAs

Sensitivity of cSensitivity of c--ANCA for ANCA for

GranulomatosisGranulomatosis with with PolyangiitisPolyangiitis

35%35%65%65%Limited WGLimited WG

65%65%95%95%Classic, multiClassic, multi--

system WGsystem WG

InactiveInactive

(treated)(treated)

DiseaseDisease

Active Active

DiseaseDisease

Case # 6Case # 6

��No history renal No history renal dzdz, sinusitis, , sinusitis,

hemoptysishemoptysis

��No prior med use, only No prior med use, only LevaquinLevaquin

��CXR RLL infiltrate, sinus films CXR RLL infiltrate, sinus films

negativenegative

�� Patient is unlikely to have Patient is unlikely to have

GranulomatosisGranulomatosis with with PolyangiitisPolyangiitis

because of because of low PPV of this testlow PPV of this test

ANCAsANCAs

�� The predictive value depends upon The predictive value depends upon

clinical presentationclinical presentation

��Negative ANCA does not exclude the Negative ANCA does not exclude the

diagnosis of AAVdiagnosis of AAV

Objective 3Objective 3

��Apply sensitivity, specificity, Apply sensitivity, specificity,

likelihood ratio and positive likelihood ratio and positive

predictive value to laboratory testing predictive value to laboratory testing

in clinical practicein clinical practice

Sensitivity and SpecificitySensitivity and Specificity

�� Sensitivity = True Sensitivity = True

Positives/Total with Positives/Total with

DiseaseDisease

�� TP/(TP+FN)TP/(TP+FN)

�� Specificity = True Specificity = True

Negatives/Total Negatives/Total

without Diseasewithout Disease

�� TN/(TN+FP)TN/(TN+FP)

True True

Neg.Neg.

(TN)(TN)

False False

PositivePositive

(FP)(FP)

Subject Subject

W/oW/o

DxDx

False False

Neg.Neg.

(FN)(FN)

TrueTrue

PositivePositive

(TP)(TP)

SubjectSubject

With With

DxDx

NegativeNegative

Test Test

ResultResult

Positive Positive

Test Test

ResultResult

Prevalence of SLE in USAPrevalence of SLE in USA

�� 2008 reported to be 100 per 100,000 2008 reported to be 100 per 100,000

adult womenadult women

��Prevalence of 0.1%Prevalence of 0.1%

��SLE in men 1/10SLE in men 1/10thth

��Does a +ANA=SLE?Does a +ANA=SLE?

Does +ANA = SLE? NODoes +ANA = SLE? NO

1,000,01,000,0

0000999,000999,00010001000

~949,000~949,0005050ANA ANA --

~50,000~50,000950950ANA +ANA +

SLESLE

NoNo

SLESLE

YesYes

If ANA 95% sensitive and 95% specific

+ANA post-test probability = 950/50,000 = 1/50 =2%

Pretest probability in random population = prevalence = 0.1%

What if ANA only 80% Specific?What if ANA only 80% Specific?

1,000,01,000,0

0000999,000999,00010001000

799,250799,250~799,200~799,2005050ANA ANA --

200,750200,750~199,800~199,800950950ANA +ANA +

Totals Totals SLESLE

NoNo

SLESLE

Yes Yes

+ANA post-test probability = 950/200,750 = 0.5%

ANA 95% sensitive and 80% specific

Pretest probability in random population = prevalence = 0.1%

Likelihood RatioLikelihood Ratio

�� Positive LRPositive LR

–– True positive rate/True positive rate/

false positive ratefalse positive rate

–– TP/FPTP/FP

�� Negative LRNegative LR

–– False neg. rate/False neg. rate/

true neg. ratetrue neg. rate

–– FN/TNFN/TN

Likelihood RatioLikelihood Ratio

�� Positive LRPositive LR–– Higher is betterHigher is better

–– LR+>5 considered good testLR+>5 considered good test

�� Negative LRNegative LR–– Lower is betterLower is better

–– LRLR--<0.2 considered good test<0.2 considered good test

�� LR+ or LRLR+ or LR-- close to 1.0: test not close to 1.0: test not predictivepredictive

�� LR multiplied by preLR multiplied by pre--test odds = posttest odds = post--test oddstest odds

LR with Low PreLR with Low Pre--test Probabilitytest Probability

�� ANA 1:40 threshold, 95% sensitivity and ANA 1:40 threshold, 95% sensitivity and specificity for given labspecificity for given lab–– LR+ = 95%/5% = 19LR+ = 95%/5% = 19

–– LRLR-- =5%/95% = 0.053=5%/95% = 0.053

�� Patient with estimated prePatient with estimated pre--test probability test probability of SLE of 1% (0.01)of SLE of 1% (0.01)

�� If ANA negative at 1:40, then postIf ANA negative at 1:40, then post--test test odds ~ 0.01x0.05 = 0.0005 (1:2000)odds ~ 0.01x0.05 = 0.0005 (1:2000)

�� If ANA positive at 1:40, then postIf ANA positive at 1:40, then post--test test odds ~ 0.01x19 = 0.19 (1:5) odds still odds ~ 0.01x19 = 0.19 (1:5) odds still strongly against having SLEstrongly against having SLE

LR with High PreLR with High Pre--test Probabilitytest Probability

�� ANA 1:40 threshold, 95% sensitivity and ANA 1:40 threshold, 95% sensitivity and specificity for given labspecificity for given lab

–– LR+ = 95%/5% = 19LR+ = 95%/5% = 19

–– LRLR-- =5%/95% = 0.053=5%/95% = 0.053

�� Patient with estimated prePatient with estimated pre--test probability test probability of SLE 50% (odds 1:1 or 1.0)of SLE 50% (odds 1:1 or 1.0)

�� If ANA is negative at 1:40, then postIf ANA is negative at 1:40, then post--test test odds ~ 1.0 x 0.5 =1:19odds ~ 1.0 x 0.5 =1:19

�� If ANA is positive at 1:40, then postIf ANA is positive at 1:40, then post--test test odds ~ 1 x 19 = odds ~ 1 x 19 = 1919 = 19:1 odds, strongly = 19:1 odds, strongly in favor of SLEin favor of SLE

Positive Predictive ValuePositive Predictive Value

��How many of test positive patients How many of test positive patients

truly have the diseasetruly have the disease

––TP/TP+FPTP/TP+FP

��Dependent on the prevalence of the Dependent on the prevalence of the

disease in the population being disease in the population being

examined (pretest probability of examined (pretest probability of

disease)disease)

Positive Predictive ValuePositive Predictive Value

PPV= (sensitivity)(prevalence)

(sensitivity)(prevalence) + (1-specificity)(1-prevalence)

Case # 6 Case # 6

�� The PPV of cThe PPV of c--ANCA is low because:ANCA is low because:

–– cANCAcANCA specificity is only 25%specificity is only 25%

–– cANCAcANCA sensitivity is only 40%sensitivity is only 40%

–– Low Low prevalanceprevalance of diseaseof disease

–– The negative likelihood ratio is highThe negative likelihood ratio is high

Case # 6Case # 6

��Does he have Does he have GranulomatosisGranulomatosis with with

PolyangiitisPolyangiitis??

��NONO

��WHY?WHY?

–– Low prevalence of diseaseLow prevalence of disease

–– 3 per 100,000 in US (0.00003%)3 per 100,000 in US (0.00003%)

Conclusions Conclusions

�� Lab tests can be supportive of the Lab tests can be supportive of the

diagnosis and useful to monitor diagnosis and useful to monitor

disease activity, disease activity, but are rarely but are rarely

diagnosticdiagnostic

�� Lab test must be interpreted in the Lab test must be interpreted in the

context of clinical presentation, and context of clinical presentation, and

understanding of sensitivity, understanding of sensitivity,

specificity, prevalence of diseasespecificity, prevalence of disease

Case # 1Case # 1

�� 28 28 yy--oo female, tired, female, tired, HAsHAs, hurts , hurts

alloverallover

��ANA 1:160ANA 1:160

��What does she have?What does she have?

�� FIBROMYALGIAFIBROMYALGIA

References References

��ACR online Advanced Rheumatology ACR online Advanced Rheumatology

CourseCourse

�� Practical RheumatologyPractical Rheumatology. 3. 3rdrd edition, edition,

2004, pp 572004, pp 57--72.72.

��Rheumatology SecretsRheumatology Secrets. 2. 2ndnd edition, edition,

Sterling G West MD, editor. 2002, pp Sterling G West MD, editor. 2002, pp

5252--62.62.

Clinical PearlsClinical Pearls

�� Upper limit of ESR for men age/2 but for Upper limit of ESR for men age/2 but for women (age + 10)/2women (age + 10)/2

�� High RF and CCP+ is highly specific for RA High RF and CCP+ is highly specific for RA and portends a worse prognosisand portends a worse prognosis

�� High RF and negative CCP: think High RF and negative CCP: think HepCHepC

�� The negative predictive value of an ANA is The negative predictive value of an ANA is high, but the PPV is lowhigh, but the PPV is low

�� Gout does not occur in premenopausal Gout does not occur in premenopausal womenwomen

�� DonDon’’t order a lab test unless it will change t order a lab test unless it will change your management planyour management plan