Download ppt - Laboratory Tests in Rheumatology Aims of lab test: 1. Identification of pathological process in the body & evaluation of its severity. 2. Support or negation

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.


• 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.


• 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



• Immunological Tests• a. Protein electrophoresis.

•. Identification of monoclonal Ab: MM, lymphoproliferative, cryoglobulins, rheumatic disease.•. Elevated -globulins.

• b. Complement.•. Immune complexes disease: SLE, SBE, severe RA.•. Monitoring lupus nephritis.• C deficiency.

• c. Autoantibodies•. Intracellular: nuclear components (ANA), cytoplasmic.•. Membranals.•. Extracellular




• 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


• Conditions associated with ANA– Systemic lupus erythematosus 95%– Systemic sclerosis 90%– Sjogren syndrome 80%– Rheumatoid arthritis 60%– Polymyositis 40%– Chronic active hepatitis 100%– Drug induced lupus 100%– Diabetes 25%– Normal 8%


• 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%).


• 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%).


• 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.


•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.



•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.


–Synovial Fluid

• Transudate of plasma enriched with high m.w. saccharides, mostly hyaluronans.

• Indication for arthrocentesis:

• .Monoarthritis (acute or chronic).

• .Infection.

• .Crystal induced arthropathy.

• .Trauma + effusion.


• Color

• Normal- yellow.

• Hemarthrosis- orange, red.

• Inflammatory arthropathy- white, cream.

• Clarity

• Normal- transparent.

• More particles and/or cells- opaque.


• Viscosity

• Normal- high.

• Inflammatory- enzymatic degradation viscosity .



•No. Cells (cells/mm)

•Normal < 200

•Non-inflammatory arthropathy < 2000•Inflammatory arthropathy> 200050,000

•Arthropathy with cells> 25,000:

– .Septic arthritis.

– .Crystal induced arthropathy.

– .Reactive arhtritis.

– .RA. Inflammatory arthropathy/ Intra-articular hemorrhage 60-80%

PMN. Non-inflammatory arthropathy Mononuclears, synoviocytes.


•Crystals

• Mono-sodium-urate Monohydrate Gout.

• Ca-pyrophosphate Dihydrate Chondrocalcinosis, Pseudogout.

• Culture
