Labs of Inflammation and Autoimmune Disease Flashcards
- Describe false positive
- Describe false negative
- person who is free of disease/condition (healthy) that tests positive for a condition
- person who has the disease/condition (affected/sick) that tests negative for that condition
- Tests that are sensitive give you what?
- Tests that are specific give you what?
- true positives (you ARE sick, are you)
- true negatives (you ARE healthy, or are you)
- Describe sensitivity.
- A test with high sensitivity picks up more (…) and has few (…)
- A test with low sensitivity has many (…)
- how sensitive is the test at correctly identifying our truly “sick” or positive pts (picking up actual disease
- more true positives; few false negatives
- many false negatives
- What is the sensitivity of the rapid antigen COVID test? Describe this if we test 100 people
- What is the sensitivity of the influenza tests? Describe this
- about 95%; out of 100 sick pts, 95 will have a true positive while 5 may have a false negative
- 50-70%; we miss out 30-50% of actual sick pts
A highly sensitive test will “pick up” on the presence of disease because it is sensitive to the (…); the test does not give up many (…), so we know that our result is one we can count on
- condition
- false negatives
- Describe specificity.
- A test with high specificity means the test is specific for that (…), and you will not get many (…) due to other conditions that may be present
- A test with low specificity will be more difficult to interpret because there can be (…) and it is not specific for (…); therefore, you are getting many (…) for the condition you are seeking
- how specific is the test for the diagnosis I am looking for
- one condition; false positives
- a variety of causes; one condition; false positives
- If my alkaline phosphatase is elevated, is it specific for one condition or possibly several?
- If my influenza test is positive, could I really have covid?
- If I have leukocytosis on a CBC, does that always mean the pt has a bacterial infection?
- no, there are possible reasons for an elevated phosphatase
- no, the specificity of the influenza test is 100%
- no, elevated WBCs are non-specific so there can be many reasons
What is a non-specific marker of infection and/or inflammation?
erythrocyte sedimentation rate (ESR)
- What is the erythrocyte sedimentation rate commonly referred to as?
- Is this test specific or non-specific?
- What is this test used as a marker for?
- This test is often used as part of a (…) of vague symptomatology
- ESR or “sed rate”
- non-specific; not diagnostic and not specific - only shows part of the picture
- inflammation, infection, tissue infarction and necrosis, neoplasm
- diagnosis
Describe the pathophysiology behind the ESR test
- erythrocytes are negatively charged and therefore repel each other
- in cases of inflammation/infection, the body releases APRs, including fibrinogen and immunoglobulins (antibodies)
- these APRs are positively charged and increase the surrounding positive charge around the erythrocytes
- this changing environment around RBCs to more neutral leads to “stacking of RBCs” called Rouleaux formation
- Rouleaux formation often indicated the presence of inflammation or infection
In a sed test, the lowest values are (…), when you have inflammation, the value (…) because it is becoming (…)
- at the top
- falls
- higher
How is the ESR test performed?
- blood is aspirated into sedimentation tube
- blood separates into plasma and RBCs over course of 60 mins
- the amount “settling” of RBCs is measured
- What is the normal value of the ESR test?
- Higher levels corresponds to what?
- 0-20 mm/l
- more stacking of RBCs = more antibodies/inflammation
Wat are RBC factors that increase ESR? Why?
anemia - except sickle cell
- less erythrocytes are present
- results in RBCs “falling down” farther in the tube
- higher ESR results
What are RBC factors that decrease the ESR? Why?
sickle cell anemia
- abnormally shaped, sickled RBCs do not fall down the tube well
erythrocytosis/polycythemia
- underlying condition results in abundance of RBCs to fill up the tube to a lower value on ESR
What conditions elevate ESR?
- inflammatory states
- autoimmune disease
- obesity
- malignancy
- age
- infection (moderate to severe)
If pts ESR is greater than 100, they most likely have an overwhelming (…) and could have a fatal outcome
bacterial infection or cancer
C-reactive protein test is a (…) marker of infection and/or inflammation
non-specific
- C-reactive protein is a (…)
- What is the function of the C-reactive protein?
- positive APR
function - recognize/respond to inflammatory mediators and target damaged tissue for clearance
- stimulated by cytokines IL-1, IL-6, and TNF
- activates the complement system
- C-reactive protein is elevated in inflammatory states, but not (…) for any disease
- C-reactive protein is synthesized in the (…) so in (…), it is unreliable as an indicator of infection/inflammation
- What is the reference range of C-reactive protein?
- not specific
- liver; liver failure
- 8-10 mg/L
A CRP level above 10 mg/L is likely to be significant. and a level about 50 mg/L is a fairly sensitive and specific indicator that there is (…) present
an overwhelming bacterial infection
What can cause a mild (>10) CRP value?
- mild respiratory infection
- pregnancy
- post-exercise
- obesity
- depression
What can cause a mild (10-50) CRP value?
- MI
- malignancy
- autoimmune disease(s)
- rheumatoid arthritis
What can cause a marked (>50) CRP value?
- overwhelming bacterial infection
- severe trauma
What determines whether we used ESR or CRP?
half-life and duration of illness
- ESR is based on the presence of (…) and (…) which have (…) half-lives
- What is the half-life of fibrinogen?
- What is the half-life of IgG?
- ESR is more commonly used in (…)
- fibrinogen, IgG, longer half-lives
- 100 hours
- 7-21 days
- chronic inflammatory processes
- CRP increases and decreases (…) once inflammation or infection resolves
- Levels increase in (…) hours
- Levels peak at (…) hours after inflammation starts
- CRP is more commonly used in (…)
- quickly
- 4-6 hours
- 36-50 hours
- acute infection/inflammation
What conditions could you order ESR for?
- eval of autoimmune diseases/widespread joint pain:
** lupus
**rheumatoid arthritis
**crohn’s disease
What conditions could you order CRP for?
- bacterial pneumonia
- cellulitis
- sepsis
- septic joint
- Procalcitonin is a precursor of (…)
- Procalcitonin levels increase during (…) but not (…) infections
- In which settings do we commonly use procalcitonin tests?
- What is the purpose of using procalcitonin tests in these settings?
- Procalcitonin tests are more frequently used in evaluation of what?
- calcitonin (regulator of calcium)
- systemic bacterial, but not viral, infections
- hospital settings (not cost-effective)
- distinguishing b/w viral and bacterial origin of cough in hospitalized pts; reduce use of inappropriate antibiotics
- sepsis; severe infection w/ unknown origin or if diagnosis is in doubt
If a patient presents with a lower respiratory tract infection, what test can you order?
procalcitonin
What are some drawbacks to using PCT (procalcitonin) to guide antibiotic use?
- more likely to be evaluated in severe pneumonia, but not necessarily all pneumonias
- many pts with pneumonia have co-existent and simultaneous viral and bacterial pathogens present
- use of PCT hasn’t been shown to improve cure rates, lengths of hospital or ICU stays, or reduce mortality rates