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First Aid 2017

Cross-Sectional Study Study looking at one particular point in time Measures disease prevalence Can show risk factors without proving causality
Case-Control Study Study comparing disease to no disease looking for risk factor Measures Odds ratio
Cohort Study Study comparing group with and without certain exposure Measures relative risk
Phase I clinical trial Small number of healthy volunteers
Phase II clinical trial Small number of patients with disease of interest
Phase III clinical trial Large number of patients randomly assigned either to the treatment under investigation or the best available treatment
Phase IV clinical trial Postmarketing surveillance or patients after treatment is approved
Sensitivity Proportion of people with disease who test positive = TP / (TP + FN)
Specificity Proportion of all people without disease who test negative = TN / (TN+FP)
Positive predictive value Proportion of positive test results that are really positive = TP / (TP+FP)
Negative predictive value Proportion of negative test results that are really negative = TN / (TN+FP)
Incidence new cases / people at risk
Prevalence existing cases / number of people
Lowering cutoff point of a test increases sensitivity and decreases specificity
Raising the cutoff point of a test increases specificity and decreases sensitivity
Odds ratio Odds that the group with the disease was exposed to a risk factor =ad/bc
Relative risk Risk of developing disease in the exposed group / unexposed = [ a/(a+b) ] / [ c / (c+d) ]
Attributable risk difference in risk between exposed and unexposed groups =[a / (a+b) } - [c / (c+d) ]
Relative risk reduction proportion of risk attributable to an intervention = 1 - relative risk
absolute risk reduction difference in risk attributable to an intervention - [c / (c+d) ] - [a / (a+b) ]
number needed to treat number of patients who need to be treated for one patient to benefit = 1 / absolute risk reduction
number needed to harm number of patients who need to be exposed to a risk factor for one patient to be harmed = 1/ absolute risk
precision consistency and reproducibility
accuracy trueness of test measurements
Selection bias error in assigning subjects to a study group resulting in an unrepresentative sample (reduced by randomization)
Berkson bias study population selected from unhealthy hospital
Recall bias People with a disease remember more
Measurement bias information is gathered in a systematically distorted manner
Procedure bias Subjects in different groups are not treated the same
Observer-expectancy bias Researcher expects certain outcome of treatment
Confounding bias A factor is related to both the exposure and the outcome
Lead-time bias early detection is confused with increased survival
Type I error Stating that there is a difference when there is none
Type II error Stating that there is no difference when there is one Power = 1 - type II error
t-test Differences between the means of 2 groups
Analysis of variance Differences between the means of 3 or more groups
Chi-squared Differences between 2 or more percentages of categorical outcomes
Autonomy Obligation to respect patients as individuals
Beneficence Duty to act in the patient's best interest
Nonmaleficence Do no harm
Patient is not adherent Figure out why and see if they would change, don't force them or refer them
Patient desires unnecessary procedure Understand why and address underlying concerns, don't refuse to see them or refer
Patient has difficulty taking medications Provide written instructions, simply treatment regimen, teach back method
Family members ask about prognosis Need patient's permission
Family member says don't tell patient Figure out why, but tell them you have to
Patient is angry about long wait time Acknowledge and apologize without explaining why
Invasive test performed on wrong patient Ethically obligated to inform patients of mistakes
Treatment not covered by insurance Don't limit or deny care
Developmental milestones in 1 year Primitive reflexes disappear, sits, uses hands, smile, separation and stranger anxiety, orients to voice and name, object permanence, and speaking
Developmental milestones in 1-2 years Walks, Stairs, stacks cubes, feeds self, kicks ball, plays with people
Developmental milestones in 3-5 years rides tricycle, draws, increased dexterity, plays away from mother, tells stories
Changes in the elderly Less REM, more suicide and fat, Worse vision, hearing, immunity, bladder control, renal, pulmonary, GI function, muscle mass
Heterochromatin Condensed, darker on EM, inactive
Euchromatin Less condensed, lighter on EM, active
DNA methylation Template strands are methylated at cytosine and adenine Mehtylation at CpG islands represses transcription
Histone methylation Reversibly represses DNA transcription (sometimes activates)
Histone acetylation Relaxes DNA coiling allowing for transcription
Purines Adenine, Guanine, 2 rings
Pyrimidines Cytosine, Uracil, Thymidine 3 rings
Deamination of cytosine uracil
G-C bond Stronger than A-T bond
Leflunomide Inhibits dihydroorate dehydrogenase which converts carbamoyl phosphate to orotic acid and uses aspartate
Orotic aciduria Impaired conversion of orotic acid to UMP which uses PRPP
Methotrexate, Trimethoprim, Pyrimethamine Inhibit dihydrofolate reductase decreasing deoxythymidine monophosphate conversion by thymidylate synthase in humans, bacteria, and protozoa.
5-fluorouracil Forms 5-F-dUMP which inhibits thymidylate synthase
6-mercaptopurine (prodrug azathioprine) Inhibits de novo purine synthesis
Mycophenolate and ribavirin inhibit inosine monophosphate dehydrogenase which converts IMP to GMP
Hydroxyurea inhibits ribonucleotide reductase which converts UDP into dUDP
Adenosine deaminase deficiency Converts adenosine to inosine. Increased dATP causes toxicity in lymphocytes, causes autosomal recessive SCID
Lesch-Nyhan Defective purine salvage due to absent HGPRT which converts hypoxanthine to IMP and guanine to GMP. Excess uric acid and PRPP. Intellectual disability, gout, self-mutilation
Unambiguous each codon specifies only 1 amino acid
Degenerate/ redundant most amino acids are coded by multiple codons
Non-overlapping continuous sequence of bases
Origin of replication Where DNA replication begins
Replication fork Y shaped region along DNA template where leading and lagging strands are synthesized
Helicase Unwinds DNA at replication fork
Single-stranded binding proteins Prevent strands from re-annealing
DNA topoisomerase Creates a single or double-stranded break in the helix to add or remove supercoils
Primase Makes RNA primer on which DNA polymerase III can initiate replication
DNA polymerase III Prokayotic elongates leading strand elongates lagging strand until reaches primer of preceding fragment 3'-5' exonuclease (proofreading)
DNA polymerase I Prokaryotic Degrades RNA primer (5'-3' exonuclease)
DNA ligase Catalyzes phosphodiester bonds within a DNA strand
Telomerase Eukaryotic RNA-dependent DNA polymerase that adds DNA to the 3' end to avoid loss of genetic material with every duplication
Created by: USMLE STEP 1



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