Diagnostic testing Flashcards
for each test, understand the biologic rationale, methods for performing, and utility/limitations of specific laboratory tests including but limited to: 1. Erythrocyte sedimentation rate, C-reactive protein, and other acute phase reactants 2. Rheumatoid factors, cryoglobulins, and circulating immune complexes 3. Anti-cyclic citrullinated peptide antibodies 4. Antinuclear antibodies and subtype specificities including anti-dsDNA, anti-Smith, anti-U1 RNP, anti-centromere antibodies, and an
What do elevated platelet factor 4 plasma levels mean in systemic sclerosis?
Elevated plasma levels of platelet factor 4 (CXCL-4) correlate with pulmonary fibrosis and pulmonary hypertension in systemic sclerosis.
What are some local conditions that cause muscle enzyme elevation?
Localized conditions that often elevate muscle enzymes include eccentric exercise induced delayed onset muscle soreness, muscle infarction in diabetes, and iatrogenic muscle injury as from intramuscular injections.
What conditions cause a low C4 but normal C3?
A low C4 with the normal C3 should prompt consideration of SLE, mixed cryoglobulinemia, membranproliferative glomerulonephritis, and hereditary angioedema. Cryoglobulinemia should prompt testing for hepatitis B and C.
C4 is lower than C3 as during intravascular consumption C3 use is lower as there are no membranes to support C3 convertase.
What causes a very low CH 50 result?
The CH50 complement measurement is less than 10 units is specific for a homozygous classical complement component deficiency. Improper handling with cold activation of complement due to immune complexes-SLE, viral hepatitis, may also cause a very low CH50.
What determines the usefulness of ANA testing?
Any well-done literature review calculating likelihood ratios showed; ANA very useful in SLE, and systemic sclerosis
ANA somewhat helpful in diagnosis for Sjogren’s syndrome, polymyositis-dermatomyositis
and a very useful for monitoring or prognosis in juvenile chronic arthritis, Raynaud’s phenomena
ANA is critical part of the diagnostic criteria and drug associated lupus, X connective tissue disease, autoimmune hepatitis.
ANA not useful with no proven value in diagnosis, monitoring, or prognosis in rheumatoid arthritis, multiple sclerosis, thyroid disease, infectious disease, ITP, fibromyalgia. 2002
What is the pre-treatment regimen for prevention of radio contrast anaphylactoid? A
Aderse reactions to radiocontrast media are anaphylactoid due to direct mast cell stimulation and premedication with 50 mg of prednisone plus Benadryl and ephedrine helps.
