Clinical Utility of
Rheumatologic Tests:
A Guide to Interpretation
Sheetal Desai MD MSEd
Questions for you…
• 1. What is the most likely diagnosis
of a patient with a positive ANA?
• 2. What is the most common cause
of an elevated ESR >100?
• 3. A preferred screening lab test has
a high sensitivity or high specificity?
• 4. Which of the following lab tests is
most specific? ESR or CRP
Common Misperceptions
• Positive result = Disease
• These tests are free, so order as
many as you want
• “money grows on
• trees”
Rheumatology Lab Tests
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Anti-CCP
ANCA
CRP
anti-Smith
ANA
dsDNA
RF
- 1998
- 1982
- 1970s
- 1966
- 1958
- 1950s
- 1948
Rheumatology Lab Tests
• Are relatively young
• Have varied sensitivity and
specificity
• Little value as a screening test
• Blind ordering can lead to diagnostic
confusion
Clinical Scenario: Case 1
• 68 year old patient presents to the ER with
fevers, chills and general malaise for one week.
• PMH: DM, HTN
• Meds: Metformin, Januvia, Norvasc, Lisinopril
• NKDA
• T 38.6 in ER, BP 110/60, HR 108
• PE: normal
• Labs: ESR 90, CRP 10mg/dl, WBC 10, Hg 12,
Plt 450,000, Cr 1.1, AST 30, ALT 28
• Ddx?
Acute Phase Proteins
• Proteins that show an increase >25% with
inflammation
• Synthesized in the liver
• Group 1- increases by 50%: C3 and
ceruloplasmin
• Group 2- increases 2-4 fold: fibrinogen,
haptoglobin, alpha 1 antitrypsin, alpha 1
chemotrypsin, alpha 1 glycoprotein
• Group 3- increases by several hundred
fold: CRP, serum amyloid A
Erythrocyte Sedimentation
Rate (ESR)
What exactly is it???
• Indirect measure of acute phase
protein fibrinogen
• Measured by the Westergren
method
• Vertical column 200-300mm long
• ESR = the distance the RBC travel
in one hour
What is a normal ESR???
• At UCI
0-20 is normal
• However ESR increases with age
and is increased in women
• For Men:
• For Women:
age/2
(age + 10)/2
Factors that Increase ESR
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Inflammatory disease
Infections
Malignancy
Increase in globulin proteins
End Stage Renal Disease
Extensive Tissue Necrosis
Pregnancy
Age
Factors that Decrease ESR
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Elevated plasma viscosity
Increased RBC’s- Polycythemia
Abnormal RBC shape- Sickle Cell
Hepatic Necrosis
Hypofibrinoginemia
Congestive Heart Failure
Extreme Leukocytosis
Trichinosis
Etiology of ESR >100
• #1 Infection
• #2 Malignancy
• #3 Rheumatologic
How to Use ESR
• Not very sensitive or specific
• Use as diagnostic criterion only for
Temporal Arteritis (TA) and PMR
• Useful in monitoring PMR, TA, RA
• Can be useful for monitoring disease
course and treatment response
• Extreme elevations in the ESR rarely
occur without evidence of serious disease
C Reactive Protein (CRP)
• What does the C stand for?
• C-polysaccharide from the
pneumococcus cell walls
• Acute phase protein- Group 3
• Exclusively produced by
hepatocytes
• Direct measure of inflammation
C Reactive Protein (CRP)
Normal Levels
<1
Moderate elevation
1-10
• See in most of the rheumatic
conditions- RA, SLE, Sjogren’s
Marked elevation
>10
• See in serious bacterial infections,
severe RA, Vasculitis, PMR
C Reactive Protein (CRP)
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Levels rise within hours of stimulus
Peaks within 2-3 days
Half life 8 hours
With effective treatment of the
underlying cause, levels can
normalize within 24-48 hours
CRP
vs.
• Rises quickly
• Falls quickly
• Direct marker of
inflammation
• Narrow range of
results
• High sensitivity
• High specificity
• High reproducibility
• NOT affected by
factors (age, gender,
anemia, RBC shape,
plasma proteins)
ESR
• Rises slowly
• Falls slowly
• Indirect marker of
inflammation
• Wide range of
results
• Mod sensitivity
• Mod specificity
• Mod reproducibility
• Affected by many
factors
Clinical Scenario: Case 1
• 68 year old patient presents to the ER with
fevers, chills and general malaise for one week.
• PMH: DM, HTN
• Meds: Metformin, Januvia, Norvasc, Lisinopril
• NKDA
• T 38.6 in ER, BP 110/60, HR 108
• PE: normal
• Labs: ESR 90, CRP 10mg/dl, WBC 10, Hg 12,
Plt 450,000, Cr 1.1, AST 30, ALT 28
• Ddx? Ur Cx and Blood cx Gram neg rods
Clinical Scenario: Case 2
• 42 year old caucasian female, otherwise
healthy, comes to clinic complaining of
fatigue. She complains of fatigue, poor
sleep habits and aches and pains over
the past year. Her joints have been
bothering her, especially her hands.
There is a discomfort and stiffness that
comes and goes, and usually involves
one hand at a time. She states that at
times her hands have been mildly swollen
and have limited her function.
Clinical Scenario
• Vitals T 99.2, BP 116/80, P 90 R 16
98%RA
• PE is unremarkable
• HEENT: WNL, no rash
• CV: RRR, no murmurs
• Pulm: CTA bilaterally
• Abd: benign, no organomegaly
• Ext: no edema, FROM of all joints, no
appreciable joint swelling in wrist, MCP,
PIP, DIP joints. No deformities. No rash
Clinical Scenario
Lab Tests:
• CBC: WBC 6.3, Hg 12.7, Plt 266
• Electrolytes: Na 138, K 4.2, Cr 0.7
• TSH 3.8 (normal 0.3-4.7)
• RF: negative
• ANA: positive, titer 1:80
ANA
What exactly are they?
• Antibodies that bind to various
antigens in the nucleus of a cell
How is it measured?
• Indirect Immunofluorescence
Antinuclear antibodies
Indirect Immunofluorescence Assay
1. Take patient serum and add it cells
2. If there are antibodies they will bind
3. Add a fluorochrome tag
4. View under a fluorescent
microscope
5. If it lights up in then positive 1:40
6. Dilute sample and repeat, 1:80,
1:160, 1:320, 1:640, 1:1280, etc
Antinuclear Antibodies
Antinuclear Antibodies
Staining Patterns
• Observer dependent
• Not sensitive
• Not specific
• Only LOOSELY associated with
certain disease states
Antinuclear Antibodies
What does the staining pattern mean?
• Homogenous
SLE
• Rim
SLE
• Speckled
Sjogren’s, MCTD
• Diffuse
nonspecific
• Nucleolar
Scleroderma
• Anti-centromere CREST
Antinuclear Antibodies
Positive ANA
• What disease states do you see it?
ANA associated Diseases
Rheumatic
Conditions
Rheumatic
Conditions
Auto- Immune Misc
Lupus
Polymyositis
Grave’s
Aging
Drug-induced
Lupus
Dermatomyositis
Primary
Biliary
Cirrhosis
Primary
Pulmonary
Hypertension
Scleroderma
RA
Hashimoto
Thyroiditis
Sjogren’s
Vasculitis
Autoimmune
Hepatitis
MCTD
ANA with age
• For every year after age 50,
percentage of ANA positivity
increases 1%/year
• For example
• Age 50
1%
• Age 55
5%
• Age 60
10%
Rheumatic Causes of
Positive ANA
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100%
99%
97%
96%
93%
80%
40%
Drug Induced Lupus
Lupus
Scleroderma
Sjogren’s
MCTD
Myositis
RA
ANA in Lupus
• Sensitivity 93-99% in SLE
• Sensitivity 95-100% in drug induced
Lupus
• Specificity is not great
• Higher the titre, higher the specificity
1:40- 30% normal population
1:160- seen in 5% of the population
Clinical Indications -ANA
• ANA is NOT a good screening test given its low
specificity
• Presence of ANA does NOT mandate the
presence of rheumatologic illness
• A negative ANA is more useful and makes Lupus
very unlikely
• ANA titers correlate poorly with disease activity
so serial measurements are not recommended
• A positive ANA with anti-centromere pattern is
very specific for limited scleroderma
Clinical Scenario: Case 2
• 42 year old caucasian female, otherwise
healthy, comes to clinic complaining of
fatigue. She complains of fatigue, poor
sleep habits and aches and pains over
the past year. Her joints have been
bothering her, especially her hands.
There is a discomfort and stiffness that
comes and goes, and usually involves
one hand at a time. She states that at
times her hands have been mildly swollen
and have limited her function.
Clinical Scenario
• Vitals T 99.2, BP 116/80, P 90 R 16
98%RA
• PE is unremarkable
• HEENT: WNL, no rash
• CV: RRR, no murmurs
• Pulm: CTA bilaterally
• Abd: benign, no organomegaly
• Ext: no edema, FROM of all joints, no
appreciable joint swelling in wrist, MCP,
PIP, DIP joints. No deformities. No rash
Clinical Scenario
Lab Tests:
• CBC: WBC 6.3, Hg 12.7, Plt 266
• Electrolytes: Na 138, K 4.2, Cr 0.7
• TSH 3.8 (normal 0.3-4.7)
• RF: negative
• ANA: positive, titer 1:80
• Anti TPO ab positive
Further testing of +ANA
• This can be done to determine the
exact nuclear target antigen
• Some of these antibodies are
specific for a particular disease
• Include dsDNA, Smith, RO/SSA,
La/SSB, U1RNP, Scl-70, centromere
Anti ds-DNA
• Specificity for SLE 97%
• Present in about 60% of pt with SLE
• Titers correlate with disease activity
in SLE
• Elevation correlates with Lupus
nephritis
• Seen in drug induced lupus
Anti- Smith
• Very specific for SLE >95%
• See in only 20-30% of patients
• No evidence that it is useful to follow
for disease activity in SLE
• Important diagnostic marker for SLE
Anti-Ro or SSA
• See in 70-97% of pt with Sjogren’s
• See in 40% of SLE - associated with
a photosensitive skin rash,
lymphopenia, and Interstitial lung
disease
• In pregnant patients, associated with
neonatal lupus and congenital heart
block
Anti-La or SSB
• Usually see along with anti-Ro/SSA
• Can see isolated activity in primary
biliary cirrhosis and autoimmune
hepatitis
Anti U1RNP
• A defining features for MCTD
• Very sensitive for MCTD, but not
specific, so use to rule out disease
• Also found in 30-40% of pt with SLE
Anti-histone Antibodies
• Seen in drug-induced lupus
• Sensitivity of 100%
• Not very specific, can see in 60-80%
Lupus
• Drugs commonly implicated:
hydralazine
INH
procainamide, penacillamine
quinidine
Anti Scl-70
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Also known as anti-topoisomerase 1
Very specific for diffuse scleroderma
Specificity is greater than 95%
Sensitivity is low, range 22-40%
Higher levels associated with greater
disease activity
• Presence correlates with a higher
risk of Interstitial Lung Disease
Anti-centromere ab
• Usually associated with
scleroderma, specifically CREST
• Also see it in SLE, Raynaud’s
• Sensitivity for Scleroderma ranges
from 30-60%
• Specificity for Scleroderma is high,
greater than 95%
Clinical Scenario: Case 3
• 69 year old male at the VA, has known
Hepatitis C. He comes into clinic
complaining of generalized aches and
pains in his joints. His left knee, right
hand and right shoulder have been
bothering him for a couple of months, and
in the morning are stiff for 15 minutes. A
Rheumatoid Factor is checked and this
returns positive.
Rheumatoid Factor (RF)
What is it?
• Autoantibody directed against the Fc
portion of IgG, can be IgM or IgA
RF positivity
• In what disease states do you see
it?
RF positive disease states
Rheumatic
Conditions
RA
Infections
SLE
MCTD
Sjogren’s
Syndrome
Systemic
Sclerosis
Cryoglobuli
nemia
TB
Leprosy
Syphilis
Sarcoidosis Leukemia
Viral
infections
Parasitic
Disease
Asbestosis
SBE
Pulmonary
Disease
Silicosis
IPF
Misc
Aging
Colon
Cancer
CirrhosisHep C/PBC
Sarcoidosis
Nonrheumatic RF+ Diseases
RF Positivity and Aging
• Frequency of a positive RF
increases with age
• Age 20-60:
• Age 60-70:
• Age>70:
2-4%
5%
10-25%
Rheumatoid Arthritis
RA
100 patients
RF +
At diagnosis
60 patients
Initially RF-, becomes RF+
during course of disease
20 patients
RF –
Seronegative RF
20 patients
Rheumatoid Factor in RA
• Sensitivity for RA: 80%
• Note that up to 40% of patients with
RA may be seronegative early on
• Specificity for RA: 80-95%
• Higher the titer or value of RF,
higher the specificity for RA
Clinical Indications for RF
• Little value as a screening test for RA
• A positive RF does NOT equate with RA
• In those patients with RA, a +RF usually
predicts more aggressive erosive disease
• Higher RF titers = higher specificity =
higher positive predictive value for RA
• Serial measurements are not indicated,
and do not correspond with disease
activity
Clinical Scenario
• 69 year old male at the VA, has known
Hepatitis C. Comes into clinic
complaining of generalized aches and
pains in his joints. His left knee, right
hand and right shoulder have been
bothering him for a couple of months, and
in the morning is stiff for 15 minutes. A
Rheumatoid Factor is checked and this
returns positive.
• Anti CCP is negative.
Anti- CCP
What are they?
• Antibodies to cyclic citrullinated peptide
• Antibodies that target citrullinated proteins
• Citrulline = a modified arginine amino acid
• May be one of the major autoantigens
driving the local immune response
Anti- CCP
• Sensitivity 50-75%
• Specificity greater than 90-95%
• Found in low frequency in other rheumatic
diseases
• May be detected in patients with early RA
• May predate the clinical development of
RA by several years
• Predictor of more erosive disease
Anti- CCP- Indications for
Clinical Use
• A disease-specific autoantibody that
is very useful for the diagnosis of RA
• Just as sensitive, and even more
specific than RF
• May predict eventual development of
RA when found in undifferentiated
arthritis
• A marker of erosive disease
ANCAs
What are they???
• Anti-neutrophil cytoplasmic
antibodies
How are they measured?
• Two step procedure
ANCAs
Step 1- Indirect Immunofluorescence Assay
1. Take patient serum and add it cells
2. If there are antibodies they will bind
3. Add a fluorochrome tag
4. View under a fluorescent microscope
5. If it lights up in the cytoplasm, then it is
Cytoplasmic-ANCA (cANCA) positive
6. If is lights up around the nucleus, then it
is Perinuclear-ANCA (pANCA) positive
7. Sensitive but not specific
Cytoplasmic-ANCA
Perinuclear-ANCA
ANCAs
Step 2- Enzyme Immunoassay
• Helps determine the specific antigen that
the antibody is binding to
• Two most common are Proteinase 3
(PR3) and Myeloperoxidase (MPO)
• Not observer dependent
• High specificity
• High positive predictive value
Cytoplasmic-ANCA
• More specific for vasculitis
• c-ANCA is associated with
proteinase 3 (PR3)
• Sensitivity reaches 90% in active
generalized Wegener’s
• Thus absence of ANCA does not
rule out Wegener’s
p-ANCA Disease States
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Microscopic Polyangiitis
Churg Strauss Syndrome
Pauciimmune Glomerulonephritis
Goodpasteur’s
Drug-Induced Vasculitis
Ulcerative Colitis
Crohn’s Colitis
Primary Sclerosing Cholangitis
Endocarditis
Malaria
Perinuclear-ANCA
• Less specific for vasculitis
• It is associated with
Myeloperoxidase (MPO)
• Helpful in differentiating polyarteritis
nodosa from microscopic polyangiitis
Clinical Indications for
ANCA testing
• Do not use it as a screening test
• Using the pr3 and MPO increases
the positive predictive value
• Controversy regarding following
ANCAs to monitor disease activity
HLA-B27
• Human Leukocyte Antigen B-27
• 95% sensitivity for Ankylosing
Spondylitis
• 80% sensitivity for Reactive Arthritis
• Low specificity
• Background prevalence of 6-10% in
caucasian populations
Rheumatologic Testing
• These labs are NOT useful as screening
test
• A positive test may or may not be
associated with the disease
• Selective ordering in patient with a high
pretest probability
•
• Ordering “Rheum Panel” is not
recommended
From Cleveland Clinic
• The diagnosis of rheumatologic diseases
is based on clinical information, blood and
imaging tests, and in some cases on
histology. Blood tests are useful in
confirming clinically suspected diagnosis
and monitoring the disease activity. The
tests should be used as adjuncts to a
comprehensive history and physical
examination.
What labs would you
order?
• 1. A patient with known lupus
admitted for flare of lupus nephritis
What labs would you
order?
• 2. A patient with inflammatory
arthritis involving PIPs, MCPs,
wrists, knees admitted for a flare
Differential Diagnosis?
• 3. 58 year old patient with fevers and
an ESR 99 and CRP of 10mg/dl