2. 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.

3. Laboratory Tests in Rheumatology
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.

4. 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

5. Laboratory Tests in Rheumatology

6. 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

7. Laboratory Tests in Rheumatology

8. Laboratory Tests in Rheumatology

9. 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

10. Laboratory Tests in Rheumatology
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%

11. Laboratory Tests in Rheumatology
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%).

12. 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%).

13. 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.

14. Laboratory Tests in Rheumatology
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.

15. Laboratory Tests in Rheumatology

16. Laboratory Tests in Rheumatology
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.

17. Laboratory Tests in Rheumatology
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.

18. Laboratory Tests in Rheumatology
Color
Normal- yellow.
Hemarthrosis- orange, red.
Inflammatory arthropathy- white, cream.
Clarity
Normal- transparent.
More particles and/or cells- opaque.

19. Laboratory Tests in Rheumatology
Viscosity
Normal- high.
Inflammatory- enzymatic degradation  viscosity .

20. Laboratory Tests in Rheumatology

21. 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  60-80% PMN.
Non-inflammatory arthropathy Mononuclears, synoviocytes.

22. Laboratory Tests in Rheumatology
Crystals
Mono-sodium-urate Monohydrate Gout.
Ca-pyrophosphate Dihydrate Chondrocalcinosis, Pseudogout.
Culture

23. Laboratory Tests in Rheumatology