Role of Laboratory Test in the. Diagnosis of Rheumatoid Arthritis. Kusworini
Handono. Medical Faculty, Brawijaya University. Malang ...
Role of Laboratory Test in the Diagnosis of Rheumatoid Arthritis
Kusworini Handono Medical Faculty, Brawijaya University Malang
Rheumatoid Arthritis • Systemic rheumatic autoimmune • Progressive and irreversible joints destruction • May have potentially devastating consequences • Average lifetime earnings loss = 50% • 40%-85% of RA patients will be unable to work within 8-10 years of disease onset • Early diagnosis and aggressive management can lead to successful control and remission
Epidemiology • Prevalence: 0.8% of the population • Affects all races, prevalence increases with age (incidence of RA is > 6x in 60-64 yo ♀ compared to 18-29 yo ♀) • Onset is most frequent during the 4th and 5th decades of life (80% at 35 – 50 yo) • ♀ : ♂ = 3 : 1 (sex differences diminish in the older age group)
Etiology The cause of RA remains unknown • Genetic predisposition : HLA-DR1, HLA-DR4 • Environmental • Smoking • Infectious agents : mycoplasma, EBV, CMV, parvovirus, rubella virus • Hormonal • Immunologic
Pathogenesis of Rheumatoid Arthritis Rheumatoid Factors, anti-CCP
B cell
Immune complexes
Complement
T cell
IFN- & Neutrophil
Antigenpresenting cells
other cytokines
Macrophage Mast cell
B cell or macrophage Pannus
Synoviocytes
TNF
Chondrocytes
IL-1 Osteoclast
Articular cartilage
Production of collagenase and other neutral proteases
Adapted from Arend WP, Dayer JM. Arthritis Rheum. 1990;33:305–15
Bone
Pathophysiology Healthy joint
Rheumatoid joint
Femur
T cells B cells
Capsule Cartilage Plasma cell
Synovial membrane
IL-6 TNF- IL-1
Synovial villi
Synoviocytes
Tibia
Angiogenesis
Pannus Eroded bone
1. Choy E and Panayi G. N Eng J Med 2001;344:907-916
Neutrophils
Radiographic features Characteristic pattern: • Small joints involvment : PIP, MCP, wrist • Juxtaarticular osteopenia • Loss of articular cartilage and bone erosions
Factors Suggesting Poor Prognosis • • • • • •
>20 swollen joints High RF titer Elevated anti-CCPs Elevated ESR Elevated CRP Late implementation of treatment
• Joint erosions • Presence of rheumatoid nodules • Socioeconomic characteristics • Smoking • Poor functional status
Laboratory Diagnostic • No laboratory tests are specific for diagnosing RA • Rheumatoid factors • Sensitivity 60 - 90 %, Specificity 50 - 60 % • The presence of rheumatoid factor is not specific for RA • RF is found in 5% of healthy persons • Number of conditions besides RA are associated with the presence of RF
Laboratory Diagnostic • Antibodies to CP • Similar sensitivity and a better specificity for RA than RF • Can be found in ± 1.5% of normal individuals • A useful test to confirm a diagnosis of RA and to estimate prognosis • CBC • ESR • Acute-phase reactant : CRP
1987 revised ACR criteria for classification of rheumatoid arthritis (RA) 1. Morning stiffness in and around joints lasting at least 1 hour before maximal improvement; 2. Soft tissue swelling (arthritis) of 3 or more joint areas observed by a physician; 3. Swelling (arthritis) of the proximal interphalangeal, metacarpophalangeal or wrist joints; 4. Symmetric swelling (arthritis) 5. Rheumatoid nodules 6. The presence of rheumatoid factor (RF) 7. Radiographic erosions and/or periarticular osteopenia in hand and/or wrist joints
• •
Criteria 1 through 4 must have been present for at least 6 weeks. Rheumatoid arthritis is defined by the presence of 4 or more criteria, and no further qualifications (classic, definite, or probable) or list of exclusions are required. In addition, a “classification tree” schema is presented which performs equally as well as the traditional (4 of 7) format. The new criteria demonstrated 91–94% sensitivity and 89% specificity for RA when compared with non-RA rheumatic disease control subjects. Arnett FC et al, Arthritis Rheum 31:315-324,1988
Classification criteria for RA (score-based algorithm: add score of categories A-D; a score of ≥ 6/10 is needed for classification of a patient as having definite RA)
A. B. C. D.
Joint involvement Serology Acute phase reactants Duration of symptoms
Aletaha et al. Arthritis & Rheumatism.2010;62:2569-81
A.Joint involvement
Score
1 large joint
0
2-10 large joints
1
1-3 small joints (with or without involvement of large joints)
2
4-10 small joint (with or without involvement of large joints)
3
>10 joints (at least 1 small joint)
5
B.Serology (at least 1 test result is needed for classification)
Negative RF and negative ACPA
0
Low positive RF or low positive ACPA
2
High positive RF or high positive ACPA
3
C.Acute Phase Reactants (at least 1 test result is needed for classification)
Normal CRP and normal ESR
0
Abnormal CRP or abnormal ESR
1
D.Duration of symptoms < 6 weeks
0
≥ 6 weeks
1 Aletaha et al. Arthritis & Rheumatism.2010;62:2569-81
Marker of Inflammation : Acute Phase Reactan • Erythrocyte Sedimentation Rate / ESR OR • C - Reactive Protein / CRP
Erythrocyte Sedimentation Rate (ESR) • ESR is the rate at which red blood cells precipitate in a period of 1 hr. • Test based on : inflammatory and necrotic processes cause an alteration in blood proteins aggregation of RBCs • Recent method automatic
Erythrocyte Sedimentation Rate (ESR) • Reference values : Men : 0-15 mm/h Women : 0-20 mm/h Child : 0-10 mm/h • Indonesian Reference value : ??? • ACR/EULAR 2010 criteria : Normal : score 0 Abnormal : score 1
C-reactive protein (CRP) • CRP is a protein found in the blood in response to inflammation (an acute-phase protein) • Produced by the liver and adipocytes • Increment is due to a rise of TNFα, IL-6, which is produced predominantly by macrophages as well as adipocytes.
CRP is an annular pentameric disc in shape.
C-reactive protein (CRP) • Reference value : < 0.3 mg/dl • Indonesian Reference value : ??? • ACR/EULAR 2010 criteria : Normal : score 0 Abnormal : score 1
Serology Markers • Rheumatoid Factor / RF
OR • Anti Citrullinated Protein Antibody / ACPA
Rheumatoid Factor • Autoantibodies reactive with epitopes in the Fc portion of IgG • IgM, IgG and IgA isotype • The RF assay : Aglutination, nephelometry, ELISA, ICT • In the general population, a test sensitivity is 60- 90% and specificity of 50-60%
IgM Rheumatoid Factor
Other causes of RF positivity l
Other connective tissue diseases
l
Viral infections
l
Leprosy
l
Leishmaniasis
l
Subacute bacterial endocarditis
l
Tuberculosis
l
Liver diseases
l
Sarcoidosis
l
Mixed essential cryoglobulinemia
Akill M, Amos RS, BMJ 310:587–590, 1995
Rheumatoid Factor • Reference value : 1 : 20 or 23 u/mL
• Indonesian reference value : ???? • ACR/EULAR 2010 criteria Negative : less than or equal to the ULN score 0 Low positive : higher than ULN but < 3 x ULN score 2 High positve : higher than 3 x ULN score 3 • If the RF value only in -/+, a positive result should be scored as low positive.
Promising biomarkers for RA : ACPAs (Anti-Citrullinated Protein-Antibodies) • • • • • • • • • • • •
Anti – PF (Perinuclear Factor) Anti - Keratin Anti - Fillagrin Anti - citrullinated Fibrin/Fibrinogen Anti - citrullinated alpha enolase Anti - CCP 1 Anti - CCP 2 Anti - CCP 3 Anti - CCP 3.1 Anti - CCP 3.2 Anti - Vimentin (Anti-Sa) Anti - MCV (Mutated Citrullinated Vimentin)
Anti Cyclic Citrullinated Peptide Antibodies
(anti-CCP) • Antibodies reactive with citrullinated fillagrin epitopes
• Useful in detecting patient with early RA (sensitivity 50-70%, specificity 95-98%) • Detection assay : ELISA, ICT • 1 st generation CCP : Ag pure cit fillagrin (sen 60 – 70 %, spec 85 %) • 2 nd generation CCP : Ag synthetic (spec 96 %) • 3 rd generation CCP : Ag ?? (spec 98%)
Reference Value (Quanta Lite) • Negative
: 20 U
• Weak Positive
: 20 – 39 U
• Moderate Positive
: 40 – 59 U
• Strong Positive
: 60 U
• Indonesian Reference Value ??? 30
ACR/EULAR 2010 : ACPA • Negative : less than or equal to the ULN score 0 • Low positive : higher than ULN but < 3 x ULN score 2 • High positve : higher than 3 x ULN score 3
Detection of Anti Citrunillated Protein Antibody (ACPA) using anti-CCP2 and anti-CCP3 in patients with Rheumatoid Arthritis in Saiful Anwar Hospital (Kusworini Handono et al, 2010) • 59 RA patients (ACR 1987), 83.1% women, age 50.13 ± 11.0 yo, dur of symptom 8.5 ± 6.6 mo, joints involvement 5.6 ± 2.2 • ACPA detection using anti-CCP2 and anti-CCP3 (Quanta Lite) • Result : - No difference level of anti-CCP2 and anti-CCP3 in RA patients (148.06 vs 185.01 U/ml ; p ACR/EULAR 2010 criteria based on 4 domain : joint involvement, serology (RF and ACPA), acute phase reactans (ESR and CRP) and duration of symptoms • Measurement of ACPA : anti-CCP or anti-Vimentin have a good sensitivity and specifisity
