1. Overview of Rheumatology Labs: Alphabet soup?
Last updated 7/24/11
Pediatric Rheumatology
Red Team Resident
Teaching Series

2. What are all those letters?
ESR
ANA
CRP
dsDNA
ENA
RNP
Smith
SS-a/SS-b
Cardiolipin
Jo-1
CPK
p-ANCA/ c-ANCA RF
C3/C4
CH50
Histone
Centromere
Scl-70
VDRL/RPR
DRVVT
Beta 2 glycoprotein 1
LDH
Aldolase

3. Background
Rheumatology spans a group of diseases that have auto-immune components
Proposed mechanisms to auto-immunity including cross reactive antigens, molecular mimicry, and autoantibody amplification
We can identify auto-antibodies and therefore characterize clinical diseases
However, presence of auto-antibodies does not always predict disease

4. Diagnostic vs. Evaluative Tests
Need to distinguish to determine which test is appropriate
Diagnostic tests accurately distinguish a group of patients with a specific disease from a non-disease group
Evaluative tests monitor disease activity over time

5. Erythrocyte Sedimentation Rate (ESR)
Mainly used as a disease activity indicator
Method: Westergren method (most common) which measures the rate of settling of RBCs in anticoagulated whole blood
Nonspecific test of inflammation
Elevated in infection, IBD, cancer, pregnancy, trauma, and stress
Can be falsely low in conditions that don’t let RBCs undergo rouleaux formation (sickle cell anemia, Hereditary Spherocytosis, CHF, polycythemia)

6. Anti-nuclear Antibodies (ANA)
Immunoglobulins directed against structures within the cell (i.e. DNA, ribonuclear proteins, histones, and centromere)
Titer is important; pattern not important
Found in a variety of autoimmune diseases such as SLE, MCTD, JRA, scleroderma, Sjogren’s syndrome in high titers (>1:320)
Almost always present in SLE (95-98%)
Low titers (<= 1:160) found in:
Infections (EBV, CMV, Hepatitis B, bacterial endocarditis, HIV)
Drugs (hydralazine, INH, dilantin, tegretol, ETX, PCN, and sulfas)
Neoplasias (lymphoma)
It is sensitive but not that specific
Consider using as a screening test in only symptomatic patients
Approximately 10% of the population has a positive low titer ANA and can be asymptomatic
ANAs do not correlate with disease activity ( i.e. diagnostic test)
If positive, should subtype (anti-dsDNA, ENA panel)
Must measure ANAs in patients with JIA to assess risk of uveitis

7. ANA Subtype: Double Stranded DNA (anti-dsDNA)
Anti-dsDNA antibody is an ANA subtype
In higher titers, highly specific for SLE
Seen in >80% of SLE patients at some time during their course
Associated with the presence of active lupus nephritis
Can detect flare up before clinically significant
Check anti-dsDNA levels if you suspect SLE in a child with positive ANA

8. ANA Subtype: Anti-Extractable Nuclear Antibodies (anti-ENA)
anti-Smith (Sm) and anti-ribonucleoprotein (RNP)
Both are directed against RNA proteins and are readily soluble in neutral buffers
Anti-RNP is specific for MCTD (high titer)
Anti-Sm ab is highly specific for SLE
10-20% in Caucasians, 30% in Asians, 40% in African Americans
One of the lupus criteria
MCTD-a syndrome of arthritis, myositis, Raynauds’, and sclerodactly

9. ANA Subtype: Anti Ro/SS-A and Anti La/SS-B
Associated with Sjogren’s, SLE, and neonatal lupus
Anti Ro/SS-A antibodies seen in:
5-15% of normals
50% of Sjogren’s patients
30% of SLE patients (many have negative ANA or subacute cutaneous lupus)
Correlates with active nephritis and cytopenias
Crosses the placenta and is associated with neonatal SLE and heart block
Anti La/SS-B antibodies seen in:
5% of normals
15-85% of Sjogren’s patients
10-15% of SLE patients
Also associated with neonatal SLE but do not see the cardiac manifestations
Sjogren’s – triad of xerophthalmia, xerostomia, and arthritis
Babies with neonatal SLE may be born to mom’s who don’t have lupus but just have the antibody
Of the mothers with lupus and +anti ro ab there is a 5% chance of heart block

10. ANA Subtype: Anticentromere, Anti-Scl-70, and Antihistone Antibodies
Anticentromere Antibodies seen in limited cutaneous systemic sclerosis
Anti-Scl-70 Antibodies (also known as anti-topoisomerase I) are assoicated with increased risk of pulmonary fibrosis in both limited and diffuse cutaneous systemic sclerosis
Anti-histone antibodies are found in 95% of patients with drug-induced lupus syndrome
Seen with:
Procainamide
Quinidine
Hydralazine
Phenytoin or other anti-epileptics
Limited cutaneous SSc — Patients with limited cutaneous SSc (lcSSc) typically have skin sclerosis restricted to the hands, and to a lesser extent, the face and neck. They also have prominent vascular manifestations and may suffer from the CREST syndrome (Calcinosis cutis, Raynaud phenomenon, Esophageal dysmotility, Sclerodactyly, and Telangiectasia).
Diffuse cutaneous SSc — Patients with dcSSc have extensive skin sclerosis and are at a greater risk for the development of significant renal, lung, and cardiac disease. The central criterion for the diagnosis of dcSSc is the extension of skin sclerosis proximal to the wrists (particularly over the proximal limbs and trunk but commonly sparing the upper back).
Studies in Japanese and European patients suggest that antibodies to topoisomerase-I (Scl-70) are associated with an increased risk of pulmonary fibrosis in both the dcSSc and lcSSc subsets. An association of either anti Th/To or anti-U11/U12 RNP autoantibodies with lung fibrosis has been observed in both limited and diffuse SSc subsets.
Anticentromere antibodies (ACA) are almost always indicative of lcSSc and are particularly seen in the classical CREST variants of this condition.

11. Antineutrophil Cytoplasmic Antibodies (ANCA)
Associated with vasculitides
Used as diagnostic test and possibly an evaluative test (still questionable)
2 main staining categories: c-ANCA and p-ANCA:
Cytoplasmic ANCA (c-ANCA) – coarse granular staining of the cytoplasm. The main antigen is proteinase-3 (PR3). Seen in 90% of Wegener’s granulomatosis.
Perinuclear ANCA (p-ANCA) – staining of the nucleus and perinuclear area leaving cytoplasm clear. Main antigen is myloperoxidase (MPO). Associated with microscopic polyarteritis nodosa, Churg-Strauss, and Ulcerative Colitis.

12. Rheumatoid Factor (RF)
Uncommon in children
Should NOT be used as a screening test for rheumatic disease in children
Only indication is for polyarticular JIA patients to classify and offer prognostic information
Low titers seen in healthy children (<5%), infections (viral, SBE), malignancy, SLE
High titers seen in JIA (<20%) and predictive of erosive joint disease (follows adult RA course more) and MCTD

13. HLA-B27 One of the histocompatibility genes
Associated with seronegative spondyloarthropathies:
ankylosing spondylitis (AS) (up to 90%)
IBD (25-50%)
psoriatic arthritis (<25%)
reactive arthritis (50-75%)
Less than 20% patients with HLA-B27 develop AS

14. Complements
Used to document complement consumption and diagnose rare complement deficiencies
CH50 (overall complement level) is decreased in SLE, MCTD, and immune complex vasculitis
Most common congenital complement deficiency is C2
Low C3 and C4 levels seen in active lupus
Complement levels help follow disease activity and response to treatment in SLE
Considered a diagnostic and evaluative test

15. Antiphospholipid Antibodies (aPL antibodies)
Group of antibodies against a variety of phospholipids and phospholipid binding plasma proteins
Associated with syndrome of coagulopathy, thrombocytopenia, recurrent spontaneous abortions, livedo reticularis, migraines, TTP, chorea, myelitis, and avascular necrosis of bone
Can occur with SLE (30-40%), or seen without other autoimmune disease (antiphospholipid antibody syndrome)
Positive anti-cardiolipin antibodies (aCL)
IgG – associated with thrombosis
IgM – associated with thrombocytopenia only
Positive lupus anticoagulant: misnomer; antibody on the phospholipid of the prothrombin activator complex that causes in vitro anticoagulation (elevated aPTT and positive DRVVT) but in vivo paradoxical thrombosis
Dilute Russell Viper Venom Test (DRVVT)
β2glycoprotein-1 IgG and IgM

16. Practice Question #1a
A 3 year old girl with a two month history of a swollen and painful knee and eye findings

17. Practice Question #1b
A 15 year old girl with multiple joint pains and joint swelling

18. Practice Question #1c
A 8 yo boy with persistent fevers, intermittent rashes, and joint pain

19. Answer for Question 1a-c: Juvenile Idiopathic Arthritis
CBC-D
ESR
ANA to determine uveitis risk
If polyarticular course, add RF
If older onset with sacroiliac tenderness and tendon insertion site tenderness, add HLA-B27
If systemic course, add LFTs, Ferritin, DDimer

20. Practice Question #2
A 13 year old Hispanic girl with a facial rash, joint pain, mouth sores, fatigue, and blood in her urine

21. Answer for Question #2: Systemic Lupus Erythematosus
CBC-D
ESR
ANA
dsDNA
C3/C4 levels
Urinalysis and Urine protein/creatinine ratio
Antiphospholipid Antibodies (Anti-cardiolipin ab, PTT, DRVVT, and LAC, B2glycoprotein)

22. Practice Question #3
A 6 year old boy with muscle weakness, leg pains, and rash over his eyelids and on his elbows

23. Answer for Question #3: Dermatomyositis
CBC-D
ESR
ANA
CPK, Aldolase, LDH (muscle enzymes)
AST/ALT (in this case, as a muscle enzyme)