Diagnostic Testing Rheumatologic and Connective Tissue Diseases

Diagnostic Testing Rheumatologic and Connective Tissue Diseases

Is it a rheumatologic or connective tissue disorder?

* The distinction between rheumatologic and connective tissue (collagen vascular) diseases is unclear.
* There is much overlap in disease presentation and laboratory testing
* In each, the body’s own proteins are recognized as foreign, and AUTO-antibodies produced


Case #1

Rheumatoid Arthritis Lab Work-up

* CBC (with diff)
* Sedimentation rate
* Rheumatoid Factor (RF)
* 40-60% have anemia of chronic disease; (suspect infection); mild WBC

Erythrocyte Sedimentation Rate (ESR)

* Nonspecific test for inflammatory process
* anticoagulated blood in calibrated tube; rate of sedimentation of RBCs in 1 hour
* normal <15m;<20f; add 10 past age 60
* Rate of sedimentation increases with
o increased fibrinogen 2 inflammatory process (occurs wi 12-24 hours)
o acute/chronic infection; tissue necrosis; tissue infarction; well established malignancy; rheumatoid/collagen diseases; abnormal serum proteins; pregnancy; obesity; anemia

Sedimentation Rate Uses

* An aid in detection and diagnosis of inflammatory condition (or to exclude)
* A means of following the activity, clinical course, or therapy of inflammatory diseases
* To demonstrate or confirm occult organic disease

Rheumatoid Factor (RF)

* RA and related diseases associated with increased immunoglobulins (autoantibodies):
o IgG variety antibodies
o IgM variety antibodies
o IgA variety antibodies
* RF is an IgM antibody directed against IgG
* Present in the sera of 75% of patients with Rheumatoid Arthritis
* Higher titer of RF are commonly associated with severe RA
* High titers also seen in syphyllis, sarcoid; infective endocarditis; TB; leprosy; parasitic infections; old age
* Presence of RF does NOT rule in RA
* Absence of RF does NOT rule out RA
* If the pretest probability of RA is high, the presence of RF is supportive of the diagnosis.
* If the pretest probability of RA is high, the absence of RF should not change your clinical diagnosis
* Order if symmetrical polyarthritis of uncertain origin
* There is no need to repeat RF testing once it is positive

Case #2

Systemic Lupus Erythematosus Lab Work-up
Antibodies in SLE
Antinuclear Antibody
(ANA)
ANA: peripheral pattern
ANA: solid/diffuse pattern
ANA: speckled pattern
Anti-nDNA Antibody
Anti-Sm Antibody

Case #3
Mixed Connective Tissue Disease Lab Work-up
Anti-RNP (ribonucleoprotein) Antibody
Case #4
Anti-RO/SSA and Anti-LA/SSB
Complement Levels
(C3, C4, CH50)
INFLAMMATION
Complement Activation Pathways
Complement Testing
HLA-B27 Antigen in Ankylosing Spondylitis
Case #5
Joint Aspirate Analysis
INFECTION

Diagnostic Testing Rheumatologic and Connective Tissue Diseases.ppt