DrVirgo
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Anti-ds DNA and Anti-SM are the specific antibodies for SLE. (so these wouldn't be too useful for screening for RA)
ANA is sensitive for SLE. ANA can be found in SLE, systemic sclerosis and Sjogren syndrome.(not sure about RA).
Diagnosis of RA is based more on clinical criteria and there is no single test or finding that will diagnose RA.
RF is found in about 70% of patients with RA. But its not specific for RA and about 5% of normal people can have RF as well. So RF is NOT a good screening test.
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| dr.Dove
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Ok thanks.
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| arlete
Attending in 2012!!!!!
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Dr Virgo:
I do not agree with you (sorry...). I think RF has good sensitivity and that makes it a good screening test. If it's not specific, then it's not a good confirmatory test.
Please, correct me if I am wrong...
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| dr.Dove
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So RF is better for screening test...not ANA.....I am reading from the kaplan notes..
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| dr in trouble
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yes ANA absence can exclude SLE but its presence cannot confirm SLE, but for RA, RF is more sensitive .
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| dr.Dove
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ohh wow...hmm....must be from lack of sleep  . I was thinking about SLE and Rheumatoid arthritis...and somehow...dont ask me how...mixed them up..when I wanted to ask a question on SLE alone.
The question for SLE was is the best screen test ANA or anti-ds DNA
Must of confused people with my post.....
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| cirus
Forum Guru
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I don't think there is a screening test for Rheumatoid arthritis, its only investgated if there is suspition of the disease, & yes RF may be +ve (70%) but there are other criteria for diag as well & only presence of RF without any of the other diag criteria doesn't confirm the diag, but I'm not sure..
anyone??
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| arlete
Attending in 2012!!!!!
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For rheumatoid arthritis, diagnosis is pretty much based on clinic presentation. No point in screening for it, you're right.
My point was: sensitivity is more important then specificity for screening tests, generally speaking. Specificity is what you want for confirmatory tests.
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| elitoki
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I agree that screening is sensitive, and confirmatory is specific.
For SLE screening test is ANA and Confirmatory is ds-DNA.
Also some autoimmune disease will give you ANA positive.
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