Rheumatology Labs:
Alphabet soup?
Pediatric Rheumatology
Red Team Resident
Teaching Series
What are all those letters?
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ESR
ANA
CRP
dsDNA
ENA
RNP
Smith
SS-a/SS-b
Cardiolipin
Jo-1
CPK
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p-ANCA/ c-ANCA
RF
C3/C4
CH50
Histone
Centromere
Scl-70
VDRL/RPR
DRVVT
Beta 2 glycoprotein 1
LDH
Aldolase
Background
• Rheumatology spans a group of diseases that have
auto-immune components
• Proposed mechanisms to auto-immunity including
cross reactive antigens, molecular mimicry, and
autoantibody amplification
• We can identify auto-antibodies and therefore
characterize clinical diseases
• However, presence of auto-antibodies does not
always predict disease
Diagnostic vs. Evaluative Tests
• Need to distinguish to determine which test
is appropriate
• Diagnostic tests accurately distinguish a
group of patients with a specific disease
from a non-disease group
• Evaluative tests monitor disease activity
over time
Erythrocyte Sedimentation
Rate (ESR)
• Mainly used as a disease activity indicator
• Method: Westergren method (most common) which
measures the rate of settling of RBCs in anticoagulated
whole blood
• Nonspecific test of inflammation
• Elevated in infection, IBD, cancer, pregnancy, trauma, and
stress
• Due to metabolic changes in liver causing increased
plasma proteins
• Can be falsely low in conditions that don’t let RBCs
undergo rouleaux formation (sickle cell anemia, Hereditary
Spherocytosis, CHF, polycythemia)
Anti-nuclear Antibodies (ANA)
• Immunoglobulins directed against structures
within the cell ( i.e. DNA, ribonuclear
proteins, histones, and centromere)
• Titer issue important; pattern not important
• Found in a variety of autoimmune diseases
such as SLE, MCTD, JRA, scleroderma,
Sjogren’s syndrome in high titres (>1:320)
• Almost always present in SLE (95-98%)
Anti-nuclear Antibodies (ANA)
• Low titres (<= 1:160) found in:
– Infections (EBV, CMV, Hepatitis B, bacterial
endocarditis, HIV)
– Drugs (hydralazine, INH, dilantin, tegretol, ETX, PCN,
and sulfas)
– Neoplasias (lymphoma)
• It is sensitive but not that specific
• Approximately 10% of the population has a
positive low titer ANA and can be asymptomatic
• As one ages, ANA titers increase (40% with low
positive ANA by age > 60 yrs)
Anti-nuclear Antibodies (ANA)
• ANAs do not correlate with disease activity
( i.e. diagnostic test)
• Consider using as a screening test in only
symptomatic patients (arthritis, rash,
serositis, proteinuria)
• Must measure ANAs in patients with JIA
(esp. oligoarticular) to assess risk of uveitis
Anti-nuclear Antibodies (ANA)
• Positive ANA is not in itself diagnostic and
should only be viewed as a clue for possible
underlying autoimmune processes. One
must use other means (PE, hx, other labs) to
make diagnosis
• If the ANA is positive, it is helpful to
further identify which antigen is being
recognized by the ANA (ANA subtype)
ANA Subtype: Double Stranded
DNA (anti-dsDNA)
• In higher titers, highly specific for SLE
• Seen in >80% of SLE patients at some time during
their course
• Associated with the presence of active lupus
nephritis
• Can detect flare up before clinically significant
• Check anti-dsDNA levels if you suspect SLE in a
child with positive ANA
ANA Subtype: Anti-Extractable
Nuclear Antibodies (anti-ENA)
• anti-Smith (Sm) and anti-ribonucleoprotein
(RNP)
• Both are directed against RNA proteins and
are readily soluble in neutral buffers
• Anti-RNP is specific for MCTD (high titer)
• Anti-Sm ab is highly specific for SLE
– 10-20% in Caucasians, 30% in Asians, 40% in
African Americans
– One of the lupus criteria
ANA Subtype:
Anti Ro/SS-A and Anti La/SS-b
• Two sets of names assigned by two different
groups; first seen in Sjogren’s patients and then
seen in SLE patients
• Anti Ro/SS-A antibodies seen in:
– 5-15% of normals
– 50% of Sjogren’s patients
– 30% of SLE patients (many have negative ANA or
subacute cutaneous lupus)
– Correlates with active nephritis and cytopenias
– Crosses the placenta and is associated with neonatal
SLE and heart block
ANA Subtype:
Anti Ro/SS-A and Anti La/SS-b
• Anti La/SS-B antibodies seen in:
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5% of normals
15-85% of Sjogren’s patients
10-15% of SLE patients
Also associated with neonatal SLE but do not
see the cardiac manifestations
ANA Subtype: Anticentromere
and Anti-Scl-70 Antibodies
• Anticentromere Antibodies seen in limited
cutaneous systemic sclerosis (CREST)
• Anti-Scl-70 Antibodies (also known as antitopoisomerase I) are assoicated with
increased risk of pulmonary fibrosis in both
limited and diffuse cutaneous systemic
sclerosis
ANA Subtype: Anti-histone
antibodies
• Anti-histone antibodies are found in 95% of
patients with drug-induced lupus syndrome
• Seen with:
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Procainamide
Quinidine
Hydralazine
Phenytoin or other anti-epileptics
Antineutrophil Cytoplasmic
Antibodies (ANCA)
• Associated with vasculitides
• Used as diagnostic test and possibly an evaluative
test (still questionable)
• 2 main staining categories: c-ANCA and p-ANCA:
– Cytoplasmic ANCA (c-ANCA) – coarse granular
staining of the cytoplasm. The main antigen is
proteinase-3 (PR3)
– Perinuclear ANCA (p-ANCA) – staining of the
nucleus and perinuclear area leaving cytoplasm clear.
Main antigen is myloperoxidase (MPO).
ANCA
• c-ANCA seen in 90% of Wegener’s
granulomatosis
• p-ANCA is associated with microscopic PAN,
Churg-Strauss, and Ulcerative Colitis
• Consider vasculitis (ANCA) if patient has:
– Fever of unknown origin
– Palpable purpura, vasculitis urticaria, or dermal
necrosis
– Mononeuritis multiplex
– Unexplained arthritis, myositis, or serositis
– Unexplained pulmonary, CV, or renal disease
– Abnormal lab: ESR or CRP, WBC or eosinophils,
low complements
Rheumatoid Factor (RF)
• Uncommon in children
• Should NOT be used as a screening test for
rheumatic disease in children
• Only indication is for polyarticular JIA patients to
classify and offer prognostic information
• Low titers seen in healthy children (<5%),
infections (viral, SBE), malignancy, SLE
• High titers seen in JIA (<20%) and predictive of
erosive joint disease (follows adult RA course
more) and MCTD
HLA-B27
• One of the histocompatibility genes
important in transplantation
• Associated with seronegative
spondyloarthropathies:
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ankylosing spondylitis (AS) (up to 90%)
IBD (25-50%)
psoriatic arthritis (<25%)
reactive arthritis (50-75%)
• Less than 20% patients with HLA-B27
develop AS
Complements
• Used to document complement consumption and
diagnose rare complement deficiencies
• CH50 (overall complement level) is decreased in
SLE, MCTD, and immune complex vasculitis
• Most common congenital complement deficiency
is C2
• Low C3 and C4 levels seen in active lupus
• Complement levels help follow disease activity
and response to treatment in SLE
• Considered an evaluative test and diagnostic test
Antiphospholipid Antibodies
(aPL antibodies)
• Group of heterogeneous antibodies against a
variety of phospholipids (cardiolipin, phosphatidic
acid, phosphatidyl-serine) and phospholipid
binding plasma proteins (beta 2 GP-1,
prothrombin, Factor X, protein C/S)
• Associated with syndrome of coagulopathy,
thrombocytopenia, recurrent spontaneous
abortions, livedo reticularis, migraines, TTP,
chorea, myelitis, and avascular necrosis of bone
• Can occur with SLE (30-40%)
Antiphospholipid Antibodies:
Screening
1. Positive anti-cardiolipin antibodies (aCL)
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IgG – associated with thrombosis
IgM – associated with thrombocytopenia only
2. Positive lupus anticoagulant: misnomer; antibody
on the phospholipid of the prothrombin activator
complex that causes in vitro anticoagulation (elevated
aPTT and positive DRVVT) but in vivo paradoxical
thrombosis
3. Dilute Russell Viper Venom Test (DRVVT)
4. β2glycoprotein-1 IgG and IgM
What tests should be ordered?
• A 3 year old girl with a two month history
of a swollen and painful knee and eye
findings
What tests should be ordered?
• A 15 year old girl with multiple joint pains
and joint swelling
What tests should be ordered?
• A 8 yo boy with persistent fevers,
intermittent rashes, and joint pain
Juvenile Idiopathic Arthritis
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CBC-D
ESR
ANA
If polyarticular course, add RF
If older onset with sacroiliac tenderness and
tendon insertion site tenderness, add HLAB27
• If systemic course, add LFTs and coags
(PT/PTT/d-dimers/fibrinogen)
What tests should be ordered?
• A 13 year old Hispanic girl with a facial
rash, joint pain, mouth sores, fatigue, and
blood in her urine
Systemic Lupus Erythematosus
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CBC-D
ESR
ANA
dsDNA
C3/C4 levels
Urinalysis and Urine protein/creatinine ratio
Antiphospholipid Antibodies (Anticardiolipin ab, PTT, DRVVT, and LAC,
B2glycoprotein)
What tests should be ordered?
• A 6 year old boy with muscle weakness, leg
pains, and rash over his eyelids and on his
elbows
Dermatomyositis
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CBC-D
ESR
ANA
CPK
Aldolase
LDH
AST/ALT
What tests should be ordered?
• A 10 year old boy with difficulty
swallowing, facial rash, joint pain, and
shortness of breath, muscle pain
Mixed Connective Tissue Disease
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CBC-D
ESR
ANA
ENA (anti-RNP and anti-Sm)
Consider Pulmonary Function Tests, ECHO,
Swallowing studies
What tests should be ordered?
• A 13 year old girl with recurrent sinusitis,
rash, cough, joint pain, and hematuria
Vasculitis
(Wegener’s Granulomatosis)
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BUN/Cre
ANCA
ESR
CBC-D
Urinalysis, Uprot/cr
vWAg
(PFTs, Sinus and Chest CT)
What tests should be ordered?
• A 17 year old woman with tightening of her
skin, tapering of her fingertips, and cold
blue hands and feet
Scleroderma
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ANA
Anti-Scl 70 antibody
Anti-centromere antibody
Antiphospholipid antibody