Dz Testing Flashcards
What are the two key features in dx of any rheumatologic disorder?
Dx is based upon the clinical features (criteria for classification) and laboratory/radiographic findings.
Diagnostic test do not make the dx
Discuss sensitivity and specificity.
Sensitivity: proportion of pts with a + test who have the dz.
SNOUT: so a negative test will effectively rule out the dz.
Specificty: proportion of pts with a negative test who do not have the dz
SPIN: so a positive test will effectively rule in a dz.
How do i screen for an autoimmune dz?
When do I order serologic tests?
Primarily by Hx and Physical… increases your PRETEST PROBABILITY*
You should have compelling reason (mod-high pretest probability) to order rheumatologic evalution
Acute Phase Reactants:
- what are these and where are they produced?
- cause
- examples
- use
What: proteins synthesized by the liver
Cause:
- inflammation….from infection, autoimmune disorders*, neoplasma
- tissue injury/necrosis from trauma and infarction
- these proteins go up and down with inflammation.
Examples:
- Coagulation proteins (I, II) fibrinogen levels increase, platelets increase
- C-reactive protein
- Complement (C3, C4, B)
- Others: fibronectin, transport proteins (Haptoglobin, Transferrin, ceruloplasmin)
Use:
- monitors dz activiy
- NOT Diagnostic
Erythrocyte Sedimentation Rate:
- definition
- pathophys of normal ESR
- pathophys of abnormal ESR
- influenced by what 3 factors
Def: the distance at which erythrocytes have settled in a vertical column of anticoagulated blood in an hour.
Patho Normal ESR:
-RBC repel one another d/t electrostatic forces (neg charges). They settle in a tube at a certain rate.
Patho Abnormal ESR:
- positively charged acute phase proteins neutralize negative charges and allow RBC to aggregate, now the RBC fall at a different rate and at a further distance.
- inflammatory states increase ESR.*
- *As pt condition changes the ESR changes relatively slowly**
Influenced by size, shape, and number of RBC (ex. ESR is increased in anemia)
ESR:
- T/F, ESR values decrease with age?
- T/F, ESR is higher in women?
- what are normal values in men, women, and children.
- How do we correct ESR for age in men and women?
False, ESR values increase with age.
True, ESR is higher among women.
Normal:
- men less than 17mm/hr
- women less than 24mm/hr
- children less than 10mm/hr
Age correction:
-men: upper limit of normal ESR = age/2
-women: upper limit of normal of ESR = (Age +10)/2
What two rheumatic conditions is ESR diagnostic of? Utility in other inflammatory diseases?
Polymyalgia rheumatica (ESR greater than 40mm/hr)
Giant cell arteritis (ESR greater than 90mm/hr)
Utility in other dz:
-limited utility for differentiating inflammatory joint dz from noninflammatry joint dz….nondiagnostic**
C-Reactive Protein (CRP):
- what is this and where is this produced?
- how does this compare to ESR?
- what is normal?
What: an acute phase reactant produced in the liver.
Comparison:
-less sensitive than ESR (age, gender, anemia), responds more quickly, but we dont always know how to interpret.
Normal CRP: less than 1 mg/L…anything higher than this is abnormal!
T/F, ESR and CRP are nonspecific indicators of inflammation, are not used in screening for rheumatic dz, and cannot differentiate one dz from another?
True.
Rheumatoid Factor:
- what is this?
- what are some conditions causing positive Rheumatoid factor?
- is this test diagnostic for RA?
Rheumatoid Factor: an auto-aby directed against Fc portion of IgG
+ rheumatoid factor:
- Rheumatoid Arthritis
- SLE
- Scleroderma
- Sjogren
- Cryoglobulinemia
- infections: hepatitis, TB, SBE, Syphilis, viral illness (mon)
- Pulmonary dz (sarcoidosis)
- Malignancy
- Lots of RF are false positives*
NO! it is not diagnostic for RA on its own, if you have a high pretest probability and + RF then your post test probability is markedly increased and this can make the dx.
What is the 2010 ACR classification Criteria of RA?
Need a total score of at least 6
- Number of synovial joints
- -2-10 large joints = 1 point
- -1-3 small joints = 2 points
- -4-10 small joints = 3 points
- -more than 10 joints = 5 points
Serological abnormality:
- Low positive (above Upper limits of Normal) = 2 points
- high positve (greater than 3x the upper limit of normal) = 3 points
Elevated acute phase proteins (CRP or ESR) above the ULN = 1 point
Sx duration of at least 6wks = 1 point
Do we retest RF in pts with established RA?
No, once the test is positive there is no value in retesting, RF does not change with dz activity
Anti-CCP (citrulline aby)
- what is this?
- MC associated with what disorder?
- how does this compare to RF?
What: aby directed against citrullinated peptides residues present within inflammatory sites.
MC associated with RA
Sensitivity equivalent to RF, greater specificity than RF. THIS IS USEFUL WHEN RF IS NEGATIVE.
Anti-nuclear abys (ANA)
- what is this?
- use
- reasons for positive ANA?
- when should i order an ANA?
Autoabys directed against nuclear ags, serologic hallmarks of systemic autoimmune disease.
Use:
- provide further diagnostic and prognostic data concerning pts who have minimal sx or who have clinical features of more than 1 autoimmune dz.
- monitor dz activity
Positive ANA:
- systemic autoimmune dz
- organ specific immune dz (hashimotos thyroiditis, graves dz, autoimmune hepatitis)
- infections (mono, hep c, SBE, HIV)
- normal ppl (false positives are generally low titiers and MC in elderly women)
Order an ANA when your pre-test probability for SLE is moderate. NOT used as random screening. ALso, not useful to dx other conditions but may support clinical dx..
There are different types of ANAs defined by their target Ag, what are these tests and what disease are they used for?
Anti-dsDNA: specific for SLE.
Anti-Sm (Smith antigen): highly specific for SLE
Anti-centromere aby (ACA): associated with CREST and scleroderma
Anti-topoisomerase I (Scl-70)- associated with diffuse scleroderma
Anti-Ro (SS-A) and La (SS-B): associated with Sjogrens
Anti-U1 snRNP: mixed connective tissue dz
Anti-Jo-1: myositis associated with interstitial lung dz. Raynauds
