Lab evaluation of rheumatic diseases

1. Lab Evaluation of Rheumatic
Diseases
Source : Clevland Clinic

2. ANA – AntiNuclear Antiboies
Can be detected in rheumatic and non-
rheumatic diseases.
Very useful in establishing diagnosis of
SLE. Sensitivity in SLE 93%-95%.

3. ANA – AntiNuclear Antiboies
ANA is positive in autoimmune diseases
which is not connective tissue , Ex.
Autoimmune hepatitis, PBC, Crohn’s
Disease.
Other Disorders , Ex. Infectious
mononucleosis , SBE, TBC,
Lymphoproliferative diseases.
Hence testing should be done when
there is clinical suspicion.

4. Different Types of ANA
And Disease Association
ANTI-dsDNA – in SLE , assess disease
activity . They are associated with lupus
nephritis. Sensitivity for Dx of SLE is 57%
and specificity of 97.4%.
ANTI-SMITH – (against small nuclear
riboprotien) – sensitivity for Dx SLE range
24%-30% , specificity 96%-98%.
ANTI-RNP – (ribonuclear protien) – coexist
with ANTI-SM in SLE . But very useful in
diagnosis of MCTD sensitivity 70%-100% ,
specificity 84%-100%.

5. Sjogren’s Syndrome Anti-Bodies
The Sjogren’s syndrome A Antigen – ANTI-
SSA/RO and ANTI-SSB/LA.
ANTI-SSA – 50%-60% seen in primary
sjogren’s , but also can be detected in RA ,
SLE , and polymoyositis .
With 2nd Sjogren’s detected in 10%-15%
and in SLE 35%-40%
ANTI-SSB – 40%-50% in primary Sjogren’s ,
and 15% in SLE . Can be also found in
autoimmune hepatitis.
If both detected in primary Sjogren’s ,
indicated more disease activity .

6. Antiribosomal P Protien Anti-
bodies
Highly specific for Lupus and associated
with neuropsychiatric lupus.
There are detected in 10%-20% of SLE.
Still diagnosis of Neuropsychiatric lupus
is based on clinical ground.

7. ANTI-HISTONE ANTIBODIES
Present in more than 95% with drug-
induced lupus, and up to 80% of
patients with idiopathic lupus.
N.B – however mere presence of
antihistone does not indicate Drug-
induce lupus , up to 80% of patient with
1-2 years of Tx with procainamed
develop positive ANA.

8. Anti-Centromere , Anti-SCL-70
Anti-Centromere – associated with
limited cutanous systemic screlosis
(CREST syndrome).
Sensitivity is 31% , specificity 97%.
Anti-SCL-70 – very useful in diagnosis of
Systemic screlosis , seen in 20.2%
specificity of 100% .
Is useful as predictor of developing of
diffuse disease .
Both can co-exist.

9. Rheumatoid factor
RF autoantibodies directed against of Fc
portion of IgG.
Positive in different disease .
Sensitivity to Dx RA is around 50%-80% ,
specificity is 85%-90%
Negative in early stage of RA , and
positivity increases over time.
Around 15%-20% RA never have RF
positive.
2%-10% of healthy person have RF positive.

10. Rheumatoid factor

11. ANTI-CCP
(Cyclic citrullinated peptide
antibodies)
Formed against citrulline residues
formed in post-translation modification
of arginine.
Sensitivity in RA is 30%-60% , specificity
95%-98% among patient meeting
criteria for RA.

12. ANTINEUTROPHILIC CYTOPLASMIC
ANTIBODIES (ANCA)
Useful in diagnosis of Wagner granulomatosis
and microscopic polyangitis.
Two-Types – C-ANACA (PR3) , And P-ANCA
(MPO).
C-ANCA in wagner granlumatosis (70%-90%) , P-
ANCA microscopic polyangitis (40%-80%).
Both can be detected in Churg-strauss and ANTI-
GBM.
Atypical ANCA pattern can be detected in
systemic vasculitis, IBD , autoimmune liver
disease , malignancies and other rheumatic
disease.