First Aid 31-54 Flashcards
Collects data from a group of people to assess frequency of a disease/related risk factors at one point in time
Cross-sectional study
A study that assesses disease prevalence
Cross-sectional study
Compares a group of people with disease to a group of people without disease; looks for prior exposure or risk factor
Case control study
A study that measures odds ratio
Case-control study
Compares a group of people with a given exposure or risk to a group of people without; can be prospective or historical
Cohort study
A study that looks to see if exposure affects the likelihood of disease
Cohort study
A study that measures relative risk
Cohort study
Compares the frequency with which both momozygotic or both dizygotic twins develop the same disease
Twin concordance study
Compares siblings raised by biological vs adoptive parents
Adoption study
Phase I clinical trial
Small number of healthy volunteers;
Is it safe?
Phase II clinical trial
Small number of patients with disease of interest;
Does it work?
Phase III Clinical trial
Large number of patients randomly assigned either to treatment or placebo/best available treatment;
Is it as good or better?
Phase IV clinical trial
Postmarketing surveillance of patients after treatment is approved;
Can it stay?
PPV equation
TP/(TP + FP)
proportion of people with the disease who test positive
NPV equation
TN/(TN + FN)
PPV and NPV vary based on
disease prevalence
Sensitivity equation
TP/(TP+FN)
the probability that all people with the disease will test positive
High sensitivity test used in screening in diseases with
low prevalence
Specificity equation
TN/(TN+FP)
Proportion of all people without the disease who test negative
High specificity test used when
A sensitivity screening test was positive
What is point A? B? C?
A = 100% sensitivity cutoff
B = practical compromise between sensitivity and specitificity
C = 100% specificity cutoff
**Lower B –> increase FP, lower FN –> increase sensitivity and NPV
Raise B –> increase FN, lower FP –> increase specificity and PPV
new cases/# people at risk
Incidence
of existing cases / population total
Prevalence
Prevalence is about the pre-test probability
(a/c) / (b/d)
Odds ratio
Odds people with disease were exposed / odds the group without disease was exposed;
Case-control studies
a/(a+b) / c/(c+d)
relative risk
cohort studies
risk of developing disease in exposed group divided by risk in unexposed group
When prevalence is low, OR is about equal to
RR
a/(a+b) - c/(c+d)
Attributable risk;
difference in risk between exposed and unexposed groups
The proportion of risk reduction attributable to the intervention as compared to the control
Relative risk reduction;
1-RR = 1- a/(a+b) / c/(c+d)
The difference in risk attributable to the intervention as compared to the control
Absolute risk reduction
c/(c+d) - a/(a+b)
NNT
1/ARR
NNH
1/AR
An increase in precision leads to
An increase in statistical power = 1-ß
The absense of random variation in a test
The absence of systematic error or bias in a test
Accuracy
The trueness of a measurement
Sampling bias is an example of
Selection bias;
Fix with randomization
Confounding bias
When a factor is related to both the disease and the outcome, but is not causal
Lead-time bias
Early detection is confused with increased survival
1 SD includes
68%
2 SDs –> 95%
3 SDs –> 99.7%
Give an example of bimodal distribution
Fast vs slow acetylators
Stating that there is an effect or difference when none exists
Type I error (alpha error);
You “a”bserved a difference that did not exist
p is judged against a pretest alpha level. If p<0.05 then
there is a less than 5% chance the study shows something that is not really there
alpha is the probability of
making a type I error
Beta is the probability of
making a type II error
Ways in increase the power of a study
increase sample size;
increase expected effect size
increase precision of measurement
The closer the absolute value of r is to +1, then
the stronger the linear correlation between the two variables;
Positive r value –> one variable up means other variable up and vice versa
Moro reflex disappears by
3 months
Rooting reflex disappears by
4 months
Palmar reflex disappears by
6 months
Babinski reflex disappears by
12 months
lifts head up by
1 month
rolls and sits by
6 months
crawls by
8 months
stands by
10 months
walks by
12-18 months
passes toy from hand to hand by
6 months
pincer grasp by
10 months
points to objects by
12 months
social smile by
2 months
stranger anxiety by
6 months
separation anxiety by
9 months
orients to mom/dad voice by
4 months
orients to name and gestures by
9 months
object permanence by
9 months
says mama and dada by
10 months
climbs stairs by
18 months
feeds self with fork and spoon by
20 months
kicks ball by
24 months
rapprochment - moves away from mom and then returns by
24 months
gender identity by
36 months
200 words and 2 word sentences by
age 2
rides a tricycle by
age 3
drawings, copies lines or circles by
age 4
hops on one foot by
age 4
uses buttons/zippers, grooms oneself by
age 5
comfortabily spends part of day away from mom by
age 3
cooperative play, has imaginary friends by
age 4
1000 words by
age 3
uses complete sentences with prepositions by
age 4;
can tell detailed stories by age 4
Sensorineural hearing loss due to destruction (often high frequency) of hair cells at cochlear base (preserved low frequency hearing at apex)
Presbycusis
change in elderly
If you are <65 and on Medicare, what are the two possible reasons?
End stage renal disease or certain disabilities
Histones are rich in what amino acids?
Lysine, Arginine
Nucleosome made of
H2A, H2B, H3, H4 all x 2
H1 stabilizes
DNA wrapped around histone
Why methylate template strang cytosine and adenine?
During DNA replication, allows mismatch repair enzymes to identify the old strand (in prokaryotes)
DNA methylation at CpG islands has what effect?
Represses transcription
CpG Methylation Makes DNA Mute
Histone methylation
Usually reversibly represses DNA transcription but can activate it in some cases (depending on location)
Histeone acetylation
Relaxes DNA coiling –> allows for transcription
Base + deoxyribose (sugar)
Nucleoside
Base + deoxyribose + phosphate
Nucleotide
Purines
2 rings
Adenine
Guanine
Pyramidines
1 ring
Cytosine
Uracil (deaminated cytosine)
Thymine
Amino acids necessary for purine synthesis
Glycine
Aspartate
Glutamine
(and THF)
MOA Leflunomide and pathway it acts in
Inhibits Dihydroorate dehydrogenase
Pathway: Pyrimidine base production
Pyrimidine base production requires
Aspartate
MOA and pathway for:
Methotrexate, Trimethoprine, Pyrimethamine
Inhibit Dihydrofolate reductase
Disrupt pryamidine synthesis
reduce dTMP being made
MOA and Pathway
5-fluorouracil
Disrupts pyrmidine synthesis
forms 5-F-dUMP
inhibits thymidylate synthase –> lowers dTMP
What drug disrupts both purine and pyramidine synthesis?
Hydroxyurea
Inhibits ribonucelotide reductase
Orotic aciduria is a failure of what pathway
Pyrimidine synthesis pathway;
can’t make UMP from orotic acid
MOA and Pathway of 6-mercaptopurine
(and its prodrug azathioprine)
inhibit de novo purine synthesis
inhibit step from PRPP –> IMP (inosine monophosphate)
MOA and Pathway for Mycophenolate and Ribavarin
Inhibit IMP (inosine monophosphate) dehydrogenase
Inhibit step from IMP –> GMP
Purine synthesis pathway
Xanthine oxidase:
Pathway, steps, inhibitors
Purine salvage pathway;
Catalyzes hypoxanthine –> xanthine and xanthine –> uric acid
Inhibited by Allopurinol, Febuxostat
Adenosine deaminase:
Pathway, step, pathology
Purine salvage pathway;
Catalyzes Adenosine –> Deoxyadenosine;
ADA deficiency major form of AR SCID –> dATP leads to toxicity in lymphocytes
HGPRT:
Pathway, step, pathology
Purine salvage pathway;
Needed for both Hypoxanthine + PRPP –> IMP and Guanine + PRPP –> GMP;
Deficiency is Lesch Nyan syndrome –> hypoxanthine gets shunted to uric acid production (X-linked recessive)
Promotors and origins of replication are rich in what bases
AT
Unwinds DNA template at replication fork
Helicase
Prevents unwound strands from re-annealing
single-stranded binding proteins
Create single or double-stranded breaks in helix to add or remove supercoils
DNA topoisomerases
What two drugs inhibit eukaryotic topoisomerase II?
Etoposide, Teniposide
What drugs inhibit prokaryotic topoisomerase II (DNA gyrase) and topoisomerase IV?
Fluoroquinolones
Primase makes an RNA primer on which ____ can initiate replication
DNA Pol III
DNA Pol III is found in
prokaryotes only
Catalyzes phosphodiester bonds between Okazaki fragments
DNA ligase
Telomerase is found
in eurkaryotes only;
often disregulated in cancer cells –> unlimited replication
Common silent mutation
Base pair change in 3rd position of codon (tRNA wobble)
Sickle cel disease, what mutation and what KIND of mutation?
glutamic acid –> valine;
Missense mutation - nucleotide substitution resulting in changed amino acid
Two examples of frameshift mutations
Duchenne MD;
Tay-Sachs
When does nucleotide excision repair occur?
G1
Nucleotide excision repair defective in
Xeroderma pigmentosum - cannot repair thymidine (pyramidine) dimers from forming with UV light exposure
Base-specific glycosylase removes altered base and creates AP site;
AP endonuclease cleaves 5’ site; Lyase cleaves 3’ site;
DNA polymerase-beta fills gap, DNA ligase seals
Base excision repair;
Occurs throughout cell cycle;
Important for repair of toxic or spontaneous deamination
Newly synthesized strand recognized, and mismatched nucleotides removed
Mismatch repair;
predominantly occurs during G2
Defective in Lynch syndrome (hereditary nonpolyposis colorectal cancer)
Brings together 2 ends of DNA fragments to repair ds breaks
Nonhomologous end joining;
Mutated in ataxia telangectasia and Fanconi anemia
Stop codons
UGA
UAA
UAG
Start codon for prokaryotes
AUG (same for eukaryotes) but codes for N-formylmethionine (fMET)
**fMET is chemotactic for neutrophils