Laboratory Testing in Rheumatology: Take the
High Value RoadWilliam E Davis, MD, FACP
Markers of inflammation◦ ESR◦ CRP
Rheumatoid factor and anti-CCP antibodies Anti-nuclear antibodies
Acute phase response◦ Cytokine production◦ Hepatic plasma proteins
↑ 25% CRP SAA Complement Ceruloplasmin Haptoglobin Fibrinogen
◦ Negative acute phase proteins albumin, prealbumin,
transferrin
Transcription factors◦ Signal transducer
and activator of transcription 3 (STAT3)
◦ Janus activated kinase (JAK)
◦ Nuclear factor κB
Inflammation
Edmund Biernacki
Robert Sanno Fåhræus
Electrostatic charges prevent rouleaux formation and sedimentation
Plasma proteins and fibrinogen ↑
Microcytosis, polycythemia ↓ Pregnancy, ESRD ↑ Normal M <15mm, F < 20 mm Elderly M = age/2 Elderly F = age/2+10
ESR: Erythrocyte Sedimentation Rate
Simple Inexpensive Strong evidence base
ESR: Advantages
Binds C-polysaccharide of streptococcus Normal <1mg/dL (<10mg/L) Binds apoptotic cells, Fcγ receptors,
activates complement >1000 fold increase in acute phase
◦ Peak 2-3 days◦ T ½ = 19h
Persistently elevated in RA, tuberculosis, malignancy
> 15 mg/dL in bacterial infection
C-Reactive Protein
Advantages◦ Modest cost◦ Automated nephelometry◦ Serum test◦ Evidence data base solid
Limitations◦ Obese, elderly, ethnicity
CRP
75 y/o caucasian male presents with new onset temporal headache x 2 weeks.
PMH: HTN, on ACE inhibitor Normal vital signs and physical examination ESR/CRP?
47 y/o female with 10 year hx rheumatoid arthritis, on MTX and tnf-inhibitor (etanercept), presents with hx acute shaking chill, cough with brick red sputum, fever, physical examination and CXR c/w RML pneumonia
ESR/CRP?
1. Evaluate the extent or severity of inflammation
2. Monitor disease activity over time and with treatment
3. Assess prognosis
Utility of ESR / CRP
Sheep cell agglutination test IgM antibodies that recognize Fc of IgG Normal: <15 I.U./L 1% young healthy, up to 5% elderly Present in RA, Sjogren’s syndrome, HCV-
cryoglobulinemia Prognostic
Rheumatoid Factor
ΥΥΥΥΥΥΥ
Anti-perinuclear factor (APF) Anti-keratin antibodies (AKA) Citrullinated filaggrin Cyclic citrullinated peptide (CCP)
Anti-Cyclic Citrullinated Peptide (CCP) Antibodies
Sensitivity 82.9% Specificity 93-94%
Predicts development of RA in early arthritis Associated with severe, destructive disease
◦ Radiographic progression◦ Total joint prosthesis◦ Disability
May precede development of RA by years◦ 30-60% CCP+ up to 6 years before dx
Anti-CCP
48 y/o male with symmetric polyarthralgia progressive x 3-4 years
Hx HTN PE: No joint swelling or deformity Lab: normal CBC, mild increase AST, ALT
<2x normal RF + 55 IU CCP negative ?
RF and Anti-CCP
48 y/o male with symmetric polyarthralgia progressive x 3-4 years
Hx HTN PE: No joint swelling or deformity Lab: normal CBC, mild increase AST, ALT
<2x normal RF + 55 IU CCP negative HCV – chronic HCV associated with RF and
arthralgia
RF and Anti-CCP
32 y/o female with symmetric polyarthralgia for 6 weeks; sx controlled with NSAID
PMHx: negative except G2P2 PE: Slight joint swelling and tenderness
MCP’s, wrists, ankles & MTP’s Lab: normal CBC, CMP, slightly elevated ESR
30, CRP 2 mg/dL RF + 55 IU CCP >100 U/ml ?
RF and Anti-CCP
1948 LE Cell 1957 FANA test
Anti-nuclear antibodiesΥ ΥΥ ΥΥΥΥΥFIT
C
Υ ΥΥ Υ
Chromatin associated antigens◦ DNA (dsDNA, ssDNA)◦ Histone ◦ Kinetochore (centromere)
Ribonucleoproteins (snRNP)◦ Sm◦ U1 RNP◦ Anti-Ro/SSA and Anti-La/SSB
Ribosomal P protein Nucleolar antigens
◦ Kenetochore ◦ Topoisomerase◦ RNA polymerase
PM-Scl-75 and PM-Scl-100 components of exoribonuclease Aminoacyl-tRNA sythetases (Jo-1)
Anti-nuclear antibodies
Fluorescent ANA test◦ Technician reads pattern and titer
Expensive Subjective (1:160 or 1:320?)
Substrate◦ Rodent liver or kidney◦ Human cultured cell lines, e.g. Hep-2
ELISA for specific antigen specificity◦ +ANA → ELISA testing
Titer Positive?1:401:801:1601:3201:6401:12801:2560>1:5120
Coat beads or microtiter plates with multiple antigens
Incubate patient plasma; measure reactivity Any reactivity - positive
-SSA/Ro-dsDNA-Sm
RNP-SSB/La-
Histone-
31 y/o female presents with pericarditis She reports intermittent joint swelling and
pain, photosensitive dermatitis WBC 3500, platelets 110,000
ANA 95% sensitive Anti-Sm specific Anti-dsDNA specific and high levels predict
renal disease
Systemic Lupus Erythematosus
65 y/o F presents with several weeks inflammatory arthritis of hands.
PMH: HTN, CHF, multiple med’s PE: swollen MCP joints Lab: normal except WBC 4000, Platelets 125,000 ANA: 1:320, homogenous
◦ Negative DNA, Sm, SSA/Ro, SSB/La Rheumatologist Rx’s hydroxychloroquine Internist discontinues hydralazine Anti-histone antibody positive
Drug induced SLE
58 y/o female has symmetric joint swelling without deformity; she has dry eyes and dry mouth and swollen parotid glands
Lab normal except hypergammaglobulinemia
RF 150 IU CCP negative ANA 1:1280 Anti-Sm, Anti-DNA neg Anti-SSA, anti-SSB positive
Sjogren’s Syndrome
32 y/o female complains of fatigue, dyspnea, joint pain, and Raynaud’s phenomenon x 6 months
PE normal except Raynaud’s Lab normal except ANA + 1:1280, nucleolar
Anti-topoisomerase (Scl70): diffuse systemic sclerosis Anti-centromere : CREST syndrome
◦ Pulmonary vascular hypertension
Raynaud’s with negative ANA: 7% risk of rheumatic disease
Raynaud’s with positive ANA: 19-30% risk of rheumatic disease
62 yo male with joint pain, Raynaud’s, and symptoms of proximal muscle weakness
CPK 2000 +ANA
40-80% PM/DM patients have +ANA Anti-Jo-1 associated with “anti-synthetase
syndrome” and interstitial lung disease
Inflammatory muscle disease
Myositis Raynaud’s, arthritis, puffy fingers Lupus or scleroderma overlap “MCTD” Anti-RNP, Anti-PM-Scl
Overlap syndromes
Negative ANA: lupus unlikely Positive ANA not helpful (%+):
◦ Discoid lupus (5-25)◦ Fibromyalgia (15-25)◦ Rheumatoid arthritis (30-50)◦ Relatives of patients (5-25)◦ Multiple sclerosis (25)◦ Thyroid disease (30-50)◦ Silicone breast implants (15-25)
Symptomatic patient with Positive ANA: look for specificity◦ Lupus: DNA and Sm specific
Anti-DNA prognostic and an activity marker Histone may indicate drug induced SSA, SSB correlate with neonatal damage
◦ Sjogren’s syndrome: SSA, SSB◦ Systemic sclerosis (SSc): 97% +ANA
Centromere: limited sclerosis and pulmonary hypertension (CREST) Topoisomerase/Scl70: diffuse disease with poor prognosis
◦ Inflammatory myositis: 40-80% + ANA, most specifics negative Anti-Jo-1 : poor prognosis and risk of pulmonary hypertension RNP , PM-Scl : associated with overlap syndromes (SLE, SSc)
Raynaud’s: ANA useful for prognosis
Summary
ESR/CRP◦ Identify extent or severity of inflammatory disease◦ Monitor disease activity (RA)◦ Assess prognosis in early arthritis
RF/CCP◦ Use anti-CCP test to improve the specificity for RA◦ +RF and +CCP predict worse prognosis
ANA◦ Very sensitive test for SLE but technically challenging◦ ANA specificities should be guided by clinical signs of
autoimmune disease◦ Prevalence of ANA specificities may be very low
Summary