Transcript Laboratory Tests in Rheumatology

Laboratory Tests in Rheumatology
• Aims of lab test:
• 1. Identification of pathological process in the body & evaluation of its
severity.
• 2. Support or negation of specific diagnosis.
• 3. Follow up of disease & complications.
• 4. Detection of adverse reactions of drug therapy.
• * Interpretation of lab tests should be done only in relation of certain
clinical context.
• Without the clinical picture most lab tests are useless.
Laboratory Tests in Rheumatology
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• Erythrocyte Sedimentation Rate ESR
The most practical indicator to acute phase response.
Not every inflammation is accompanied by elevated ESR,
especially if mild or chronic.
Reflects mainly fibrinogen and immunoglobulins.
Roles:
1. Indicator to organic disease (nonspecific).
2. Monitoring disease activity.
3. Monitoring response to therapy.
Values: men- age/2; women- (age+10)/2.
Laboratory Tests in Rheumatology
• C-reactive protein
– Biological ligands: phosphocholine, phospholipids,
histone
– Activation of classic complement pathway
– Interaction with immunocytes by binding to Fc
gamma receptor
– Sensitive marker of inflammation
Laboratory Tests in Rheumatology
Laboratory Tests in Rheumatology
•Immunological Tests
• a. Protein electrophoresis.
•. Identification of monoclonal Ab: MM, lymphoproliferative,
cryoglobulins, rheumatic disease.
•. Elevated g-globulins.
• b. Complement.
•. Immune complexes disease: SLE, SBE, severe RA.
•. Monitoring lupus nephritis.
• C deficiency.
• c. Autoantibodies
•. Intracellular: nuclear components (ANA), cytoplasmic.
•. Membranals.
•. Extracellular
Laboratory Tests in Rheumatology
Laboratory Tests in Rheumatology
Laboratory Tests in Rheumatology
• Anti-cyclic citrullinated peptide antibodies
– Directed against citrulline residues formed in post
translational modifications of arginine
– Highly specific (98%)
– Moderately sensitive (68%)
– Marker of prognosis or of disease severity
Laboratory Tests in Rheumatology
• Conditions associated with ANA
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Systemic lupus erythematosus
Systemic sclerosis
Sjogren syndrome
Rheumatoid arthritis
Polymyositis
Chronic active hepatitis
Drug induced lupus
Diabetes
Normal
95%
90%
80%
60%
40%
100%
100%
25%
8%
Laboratory Tests in Rheumatology
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Anti-DNA
SLE.
. Marker for disease activity.
. In correlation with kidney damage.
• Anti- Histone
• 95% 0f patients with drug lupus (procainamide, quinidine,
hydralazine, phenitoin)
•  fever, arthritis, respiratory symptoms.
• Anti- Sm
• Specific for SLE.  Sensitivity (30%).
Laboratory Tests in Rheumatology
• Anti- RNP
• Specific to U1 RNA.
• Specific to MCTD (100%).
• Anti- Centromere
• 80-90% of cases with limited scleroderma.
• Anti- Scl-70
• Scl-70 = DNA topoisomerase I, an intracellular enzyme
involved in the initial uncoiling of DNA.
• Specific to diffuse scleroderma.  Sensitivity (10-20%).
Laboratory Tests in Rheumatology
• Anti-ssA
• SsA shows homology to calreticulin- Ca binding intracellular
protein.
– . SLE.
– . Neonatal lupus.
– . Sjogren syn. especially + extra-articular manifestations.
– . Subacute cutaneous lupus.
• Anti-ssB
• ssB =RNA binding protein.
– . Sjogren syn.
– . SLE.
Laboratory Tests in Rheumatology
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Anti-neutrophil cytoplasmic Abs
Abs against cytoplasmic Ags in PMN>> Monocytes.
2 principal forms:
1.C-ANCA. Cytoplasmic granular staining. Anti-proteinase 3.
Specific to Wegener’s granulomatosis.
In active disease up to 90%. In remission 30%.
Possible marker for disease activity.
2. P-ANCA. Perinuclear staining. Anti-myeloperoxidase.
Non specific marker of necrotizing vasculitis:
– . Churg-Strauss.
– . MPA.
– . GN.
Laboratory Tests in Rheumatology
Laboratory Tests in Rheumatology
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HLA •
B-27: 90% of AS patients. 8% normal population.
DR-4: 67% of white population with RA. 30 % of normals.
* Useless as routine test.
* Take B-27 when high clinical suspicion for AS + normal X film.
Laboratory Tests in Rheumatology
Synovial Fluid –
• Transudate of plasma enriched with high m.w. saccharides,
mostly hyaluronans.
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Indication for arthrocentesis:
.Monoarthritis (acute or chronic).
.Infection.
.Crystal induced arthropathy.
.Trauma + effusion.
Laboratory Tests in Rheumatology
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Color
Normal- yellow.
Hemarthrosis- orange, red.
Inflammatory arthropathy- white, cream.
• Clarity
• Normal- transparent.
• More particles and/or cells- opaque.
Laboratory Tests in Rheumatology
• Viscosity
• Normal- high.
• Inflammatory- enzymatic degradation  viscosity .
Laboratory Tests in Rheumatology
Laboratory Tests in Rheumatology
•No. Cells (cells/mm)
•Normal < 200
•Non-inflammatory arthropathy < 2000
•Inflammatory arthropathy> 200050,000
•Arthropathy with cells> 25,000:
– .Septic arthritis.
– .Crystal induced arthropathy.
– .Reactive arhtritis.
– .RA.
 Inflammatory arthropathy/ Intra-articular hemorrhage  6080% PMN.
 Non-inflammatory arthropathy Mononuclears,
synoviocytes.
Laboratory Tests in Rheumatology
Crystals •
• Mono-sodium-urate Monohydrate Gout.
• Ca-pyrophosphate Dihydrate Chondrocalcinosis,
Pseudogout.
• Culture
Laboratory Tests in Rheumatology