case 5 - headache & fever Flashcards
What 2 measures of clinical sign accuracy are characteristics of the test?
Sensitivity, specificity
What is the sensitivity of a clinical test?
The proportion of people with disease who have a positive test (true positive)
What is the equation for the sensitivity of a clinical test?
a/(a+c)
What is the specificity of a clinical test?
The proportion of people without a disease who have a negative test (true negative)
What is the equation for the specificity of a clinical test?
d/(b+d)
What are the predictive values of a clinical sign?
The likelihood that person with a certain test result has the correct result
What are predictive values of a clinical test affected by?
The prevalence of the disease and therefore the pretest probability of having the disease
What is the positive predictive value of a clinical test?
The proportion of patients with a positive test that are correctly identified as having the disease
What is the negative predictive value of a clinical test?
The proportion of patients with a negative test who do not have the disease
What is the pre-test probability in a clinical test?
The chance that a patient has the disease, based on the proportion of people in the community that have the disease (the prevalence)
What is the equation for the positive predictive value of a clinical test?
a/(a+b)
What is the equation for the negative predictive value of a clinical test?
d/(c+d)
What does the letter a represent in a 2 by 2 table for a clinical test?
true positives
What does the letter b represent in a 2 by 2 table for a clinical test?
false positives
What does the letter c represent in a 2 by 2 table for a clinical test?
false negatives
What does the letter d represent in a 2 by 2 table for a clinical test?
true negatives
When performing a number of tests one after the other for the same disease, are the tests dependent or independent?
Independent
In 2 consecutive clinical tests, how is the prior predictive value of the second test calculated?
As the positive predictive value of the first (if 1st test is positive), or the negative predictive value minus 1 (if the test is negative)
What are the 3 key acute phase proteins measured in patients with acute inflammation.
Coagulation proteins, Alpha-1-Antitrypsin, C-Reactive Protein
What happens to levels of coagulation proteins in the acute inflammatory response?
Typically elevated
What is the function of the acute phase protein Alpha-1-Antitrypsin?
protects the body from inflammatory agents by binding to elastase
What happens to Alpha-1-Antitrypsin levels in response to acute inflammation?
Elevated
What is the key role of CRP in acute inflammation?
Activation of the complement system
What are the 4 key stimuli that trigger acute inflammation?
Pathogens/microorganisms, chemical agents, inappropriate immunological response, tissue death
How do pathogens/microorganisms trigger acute inflammation?
Viruses cause cell damage, while bacteria produce endotoxins, which is detected by immune cells
How does tissue damage trigger acute inflammation?
Dead, necrosed cells release cellular contents, which includes proteins and chemicals hat attract phagocytes and other leukocytes to the area.
What are the gross changes in coagulation necrosis?
Pale area
What are the gross changes in gangrenous necrosis?
Black area
What are the gross changes to the brain/meninges in meningitis?
congestion (redness, blood vessels), swelling (widening of gyri, narrrowing of sulci), pus accumulation
What are the 2 key microcopic responses occuring in the acute inflammatory response?
Vascular response, cellular response
What are the processes occuring in the vascular component of the acute inflammatory response?
blood vessel dilation, increased vessel permeability, vascular congestion, increased blood viscosity (incr. RBC conc.), white blood cells slowing down
What are the processes occuring in the cellular component of the acute inflammatory response?
leukocytes leave the vasculature and enter the site of inflammation to participate in phagocytosis and degranulation, releasing chemical mediators to attract more cells to the area.
What are the 6 steps through which leukocytes leave the vasculature and enter the site of inflammation?
Margination, rolling, adhesion, transmigration, chemotaxis, activation
What is exudate, and what is its function?
A protein rich fluid formed due to increased vascular permeability to fluid, that aids in the local inflammatory responses
What does exudate deliver to the site of inflammation?
Immune plasma proteins, chemical mediators, leukocytes
What are cytokines released by?
macrophages
What are the key pro-inflammatory cytokines (3)?
IL-1, IL-6, TNF alpha
What is the role of TNF alpha in the acute inflammatory response?
vasodilation, vascular leakage, fever, hyperalgesia, leukocyte recruitment to site of inflammation
What is the role of IL-1 in the acute inflammatory response?
fever, hyperalgesia, leukocyte recruitment to site of inflammation
What is the role of IL-6 in the acute inflammatory response?
fever, hyperalgesia, leukocyte recruitmenr