Flashcards in Diagnosis of autoimmune diseases Deck (18):
measure of how good is the test in identifying people with the disease
measure of how good is the test at correctly defining people without the disease
define positive predictive value.
The proportion of people with a positive test who have the target disorder
define negative predictive value
The proportion of people with a negative test who do not have the target disorder.
What are the 2 types of diagnostic test available
2- Disease specific.
What types of tests are included in non-specific markers
ESR- if inflammation, thicker blood results in longer sedimentation rate.
CRP-produced by liver in response to inflammation
Ferritin- level increase
Fibrinogen- level increase
Haptoglobin- level decrease (synthetic capacity of liver is reduced)
Albumin- level decrease (synthetic capacity of liver is reduced)
Complement- level decreases and CD3 and CD4 are actively used up
What test follows a positive ANA.
ENA-extractable nuclear antigen.
• The 4-test ENA panel is used to help diagnose mixed connective tissue disease (MCTD), systemic lupus erythematosus (SLE), and Sjögren syndrome.
• The 6-test ENA panel can also help identify scleroderma (systemic sclerosis) and polymyositis/dermatomyositis (inflammatory
How is a ANA test conducted
• Use fibroblast and expose cell nuclei
• Add serum of patient
• Primary reaction-antibody if present, attaches to the antigen
• Secondary reaction-secondary autoantibody, which has a fluorescence tag, is used to attaches to the antibody/antigen complex, which is formed.
• Detection of ANA does not mean that it is an autoimmune condition as it can be found in someone with flu
What type of sensitivity and specificity is the ANA test
high sensitivity but low specificity.
What type of sensitivity and specificity is the dsDNA (for lupus) and ENA
high specificity and low sensitivity.
How is multiplex assessment of non-organs specific autoantiobodies with novel micro bead based immunoassays carried out
• Beads, present with internal colouring which can be identified by a detector.
• Antigen attached to bead
• Attack the bead with a specific antibody.
• Use a secondary antibody to show which antibodies have stuck to which antigens- has flurescence
• Measure 20-30 different antibodies with 1 serum test
• Disadvantage- doesn’t show autoantibodies for antigens, which aren’t tested.
What conditions is Rheumatoid factor present in.
• Commonly found in rheumatoid arthritis but not diagnostic of the diseases
Can be preset in the flu.
• Can be seen with other diseases in which polyclonal stimulation of B cells is seen
Is Anti-CCP (ACPA)- anti-cyclic citrullinated peptide more specific for rheumatoid arthritis than RF
• Specific to citrulline factor which presents in cell death from argilline.
What condition does ANCA test for
What are the 2 main types of ANCA which can be tested
What condition does a positive test of anti- mitochondrial Ab
primary biliary sclerosis
What condition does a positive test of anti- smooth muscle and anti-liver/kidney/microsomal (LKS) Abs