MDSC 515 CORE EXAM STUDY 2025/2026 QUESTIONS
AND SOLUTIONS GRADED A+ TIP
✔✔observational research studies - ✔✔-no direct intervention by the researcher
-case report: single case
-case-series: multiple instances of disease
-cohort: multiple instances of exposure
-case-control: comparing exposure data in patients who have the disease (cases) and
those who dont (controls)
✔✔experimental research studies - ✔✔-specific intervention by the researcher
-diagnostic test studies - may be experimental or observational
-RCTs - randomized
✔✔retrospective vs prospective research - ✔✔-retrospective looks back into the past to
collect data
-prospective progresses into the future to collect data - controlled variables/exposures
✔✔observational retrospective studies - ✔✔-case report
-case control
-case studies
-all of the situations where the individuals already have the disease and we look back to
determine potential associations with exposures
✔✔observational prospective studies - ✔✔-cohort
-individuals have yet to develop the disease but have the risk factors so we watch to
see if they develop it
✔✔diagnostic test studies - ✔✔-when testing a novel diagnostic test against a reference
standard
-can be retrospective in the sense they use information from the past or prospective in
that they follow individuals in the future
-involves individuals either with the disease or suspected to have the disease as well as
controls
✔✔Critical appraisal - ✔✔-how to we determine if evidence should be included
-is any evidence considered sufficient
-is bad quality evidence better than no evidence
-is there methods to appraise evidence
✔✔GRADE - biomedical appraisal - ✔✔-Grading of Recommendations, Assessment,
Development and Evaluations
-critical appraisal tools for high-level appraisal of medical studies
,✔✔GRADE certainty ratings - ✔✔-very low: the effect is probably markedly different
from the estimated effect
-low: the true effect might be markedly different from the estimated effect
-moderate: true effect is probably close to the estimated effect
-high: confidence that the true effect is similar to the estimated effect
✔✔why would certainty be rated down - ✔✔-risk of bias - flaws in study design or data
reporting
-imprecision - uncertainty of effect of magnitude (Confidence interval)
-inconsistency - contrasts with other studies
-indirectness - population does not match study cohort or the outcomes of interest are
just surrogates of the outcome of interest - believe to be indicative of the outcomes
-publication bias - studies published just report anticipated outcomes or effects
✔✔why would certainty be rated up - ✔✔-large magnitude of effect
-dose-response gradient
-all confounders would decrease magnitude of effect (when there is an effect)
✔✔subtypes of variables - ✔✔-ordinal - all integers
-continuous - real numbers
-nominal - non-numerical - like colours
✔✔event possibility - ✔✔-when there is an observation, what are all the possible
outcome events
✔✔event probability - ✔✔-measure of the frequency of a given event when a series of
events are observed
✔✔relative frequency - ✔✔-actual probability of an event is unknown
-the relative frequency is the number of observations over time divided by the total
number of observations over that time
-associated error measure - need to do it enough times to ensure it is validated
✔✔accuracy - ✔✔measure of nearness of a given measurement to a reference point
✔✔precision - ✔✔measure of consistency of a set of measurements
✔✔prevalence - ✔✔-number of cases per sample of population evaluated
✔✔incidence - ✔✔-number of new cases per sample of population evaluated per time
period
✔✔tests of categorical variables - ✔✔relative risk, odds ratio, sensitivity/specificity
,✔✔risk ratio - ✔✔-ratio of risk in disease in exposed individuals versus the risk of
disease in non-exposed individuals
✔✔Odds ratio - ✔✔-ratio of odds that a case was exposed versus odds that controls
were exposed
-odds of disease in the exposed over odds of disease in non-exposed
✔✔use of OR and RR in studies - ✔✔- can be used to measure the association
-odds ratio used in case-control - see the individuals with the disease compared to
without
-RR cannot be used for it as the control may not accurately represent the population
✔✔hazard ratio - ✔✔-ratio of a hazard in the presence of a
predictor/intervention/exposure to the hazard without
-HR<1 = reduction in the hazard in the presence of the predictor/indicator relative to the
baseline
-HR = 1 = no difference over the baseline
-HR>1 indicates an increase in the hazard in the presence of the predictor/indicator
relative to the baseline
✔✔sensitivity - ✔✔-how well a test correctly detects individuals with the condition of
interest
-minimizes false negatives
✔✔specificity - ✔✔-how well the test correctly identifies individuals without the condition
of interest
-minimizes false positives
✔✔Positive predictive value - ✔✔-probability that a positive test is correct
✔✔negative predictive value - ✔✔-probability that a negative test is correct
✔✔positive likelihood ratio - ✔✔-how much more likely individuals with the condition are
to have a positive test result
✔✔negative likelihood ratio - ✔✔-how much less likely individuals with the condition are
to have a negative test result
✔✔Receiver operator characteristic - ✔✔-plot of sensitivity vs 1-sensitivity
-statistical assessment of validity of the test
✔✔correlation - ✔✔-the degree to which a pair of continuous variables are linearly
related
, ✔✔p-value - ✔✔-probability of rejecting the null hypothesis when it is true
✔✔clinical significance - ✔✔-magnitude of the actual treatment effect
✔✔type 1 error - ✔✔-alpha
-false positive result
✔✔type 2 error - ✔✔-B
-false negatives
✔✔phospholipids - ✔✔-glycerol backbone
-two hydroxyl groups connected to fatty acids or acyl groups
-third hydroxyl group esterfied to phosphate and then to a head group that determines
name and function
-hydrophilic head and hydrophobic tail (amphipathic)
✔✔cell membrane - ✔✔-phospholipids form bilayer
-hydrophilic outside and hydrophobic inside
-fluid bilayers - cholesterol to stiffen, phospholipids and proteins
-mosaic membrane
-species interacting affect the fluidity of the membrane and cell polarity
-phospholipids can move around the bilayer by diffusion
✔✔proteins in cell membranes - ✔✔-can function together as large complexes
-can be aggregated to diffuse laterally through membrane
-intramolecular forces will affect them
-functions: ion and metabolite transport, fluid phase and uptake of molecules, can
diffuse through membrane but cannot flip surfaces
✔✔when do lipid rafts form - ✔✔-associations between architecturally similar
phospholipids due to intermolecular interactions
✔✔external environment interface - ✔✔-organization of the membrane is important for
cell-cell interactions and signalling and cell-matrix interactions
-surface has carbohydrates - chemical and mechanical barrier involved in cell-cell and
cell-matrix interactions
-contains receptors for intracellular signalling pathways - movement across the
membrane is limited so this links the outside to the inside
✔✔cell membrane permeability - ✔✔-passive diffusion of small non-polar molecules,
hydrophobic molecules and small polar molecules
-is a barrier against larger polar molecules as we do not want these larger molecules
within the cells
-impermeable against ions no matter the size
AND SOLUTIONS GRADED A+ TIP
✔✔observational research studies - ✔✔-no direct intervention by the researcher
-case report: single case
-case-series: multiple instances of disease
-cohort: multiple instances of exposure
-case-control: comparing exposure data in patients who have the disease (cases) and
those who dont (controls)
✔✔experimental research studies - ✔✔-specific intervention by the researcher
-diagnostic test studies - may be experimental or observational
-RCTs - randomized
✔✔retrospective vs prospective research - ✔✔-retrospective looks back into the past to
collect data
-prospective progresses into the future to collect data - controlled variables/exposures
✔✔observational retrospective studies - ✔✔-case report
-case control
-case studies
-all of the situations where the individuals already have the disease and we look back to
determine potential associations with exposures
✔✔observational prospective studies - ✔✔-cohort
-individuals have yet to develop the disease but have the risk factors so we watch to
see if they develop it
✔✔diagnostic test studies - ✔✔-when testing a novel diagnostic test against a reference
standard
-can be retrospective in the sense they use information from the past or prospective in
that they follow individuals in the future
-involves individuals either with the disease or suspected to have the disease as well as
controls
✔✔Critical appraisal - ✔✔-how to we determine if evidence should be included
-is any evidence considered sufficient
-is bad quality evidence better than no evidence
-is there methods to appraise evidence
✔✔GRADE - biomedical appraisal - ✔✔-Grading of Recommendations, Assessment,
Development and Evaluations
-critical appraisal tools for high-level appraisal of medical studies
,✔✔GRADE certainty ratings - ✔✔-very low: the effect is probably markedly different
from the estimated effect
-low: the true effect might be markedly different from the estimated effect
-moderate: true effect is probably close to the estimated effect
-high: confidence that the true effect is similar to the estimated effect
✔✔why would certainty be rated down - ✔✔-risk of bias - flaws in study design or data
reporting
-imprecision - uncertainty of effect of magnitude (Confidence interval)
-inconsistency - contrasts with other studies
-indirectness - population does not match study cohort or the outcomes of interest are
just surrogates of the outcome of interest - believe to be indicative of the outcomes
-publication bias - studies published just report anticipated outcomes or effects
✔✔why would certainty be rated up - ✔✔-large magnitude of effect
-dose-response gradient
-all confounders would decrease magnitude of effect (when there is an effect)
✔✔subtypes of variables - ✔✔-ordinal - all integers
-continuous - real numbers
-nominal - non-numerical - like colours
✔✔event possibility - ✔✔-when there is an observation, what are all the possible
outcome events
✔✔event probability - ✔✔-measure of the frequency of a given event when a series of
events are observed
✔✔relative frequency - ✔✔-actual probability of an event is unknown
-the relative frequency is the number of observations over time divided by the total
number of observations over that time
-associated error measure - need to do it enough times to ensure it is validated
✔✔accuracy - ✔✔measure of nearness of a given measurement to a reference point
✔✔precision - ✔✔measure of consistency of a set of measurements
✔✔prevalence - ✔✔-number of cases per sample of population evaluated
✔✔incidence - ✔✔-number of new cases per sample of population evaluated per time
period
✔✔tests of categorical variables - ✔✔relative risk, odds ratio, sensitivity/specificity
,✔✔risk ratio - ✔✔-ratio of risk in disease in exposed individuals versus the risk of
disease in non-exposed individuals
✔✔Odds ratio - ✔✔-ratio of odds that a case was exposed versus odds that controls
were exposed
-odds of disease in the exposed over odds of disease in non-exposed
✔✔use of OR and RR in studies - ✔✔- can be used to measure the association
-odds ratio used in case-control - see the individuals with the disease compared to
without
-RR cannot be used for it as the control may not accurately represent the population
✔✔hazard ratio - ✔✔-ratio of a hazard in the presence of a
predictor/intervention/exposure to the hazard without
-HR<1 = reduction in the hazard in the presence of the predictor/indicator relative to the
baseline
-HR = 1 = no difference over the baseline
-HR>1 indicates an increase in the hazard in the presence of the predictor/indicator
relative to the baseline
✔✔sensitivity - ✔✔-how well a test correctly detects individuals with the condition of
interest
-minimizes false negatives
✔✔specificity - ✔✔-how well the test correctly identifies individuals without the condition
of interest
-minimizes false positives
✔✔Positive predictive value - ✔✔-probability that a positive test is correct
✔✔negative predictive value - ✔✔-probability that a negative test is correct
✔✔positive likelihood ratio - ✔✔-how much more likely individuals with the condition are
to have a positive test result
✔✔negative likelihood ratio - ✔✔-how much less likely individuals with the condition are
to have a negative test result
✔✔Receiver operator characteristic - ✔✔-plot of sensitivity vs 1-sensitivity
-statistical assessment of validity of the test
✔✔correlation - ✔✔-the degree to which a pair of continuous variables are linearly
related
, ✔✔p-value - ✔✔-probability of rejecting the null hypothesis when it is true
✔✔clinical significance - ✔✔-magnitude of the actual treatment effect
✔✔type 1 error - ✔✔-alpha
-false positive result
✔✔type 2 error - ✔✔-B
-false negatives
✔✔phospholipids - ✔✔-glycerol backbone
-two hydroxyl groups connected to fatty acids or acyl groups
-third hydroxyl group esterfied to phosphate and then to a head group that determines
name and function
-hydrophilic head and hydrophobic tail (amphipathic)
✔✔cell membrane - ✔✔-phospholipids form bilayer
-hydrophilic outside and hydrophobic inside
-fluid bilayers - cholesterol to stiffen, phospholipids and proteins
-mosaic membrane
-species interacting affect the fluidity of the membrane and cell polarity
-phospholipids can move around the bilayer by diffusion
✔✔proteins in cell membranes - ✔✔-can function together as large complexes
-can be aggregated to diffuse laterally through membrane
-intramolecular forces will affect them
-functions: ion and metabolite transport, fluid phase and uptake of molecules, can
diffuse through membrane but cannot flip surfaces
✔✔when do lipid rafts form - ✔✔-associations between architecturally similar
phospholipids due to intermolecular interactions
✔✔external environment interface - ✔✔-organization of the membrane is important for
cell-cell interactions and signalling and cell-matrix interactions
-surface has carbohydrates - chemical and mechanical barrier involved in cell-cell and
cell-matrix interactions
-contains receptors for intracellular signalling pathways - movement across the
membrane is limited so this links the outside to the inside
✔✔cell membrane permeability - ✔✔-passive diffusion of small non-polar molecules,
hydrophobic molecules and small polar molecules
-is a barrier against larger polar molecules as we do not want these larger molecules
within the cells
-impermeable against ions no matter the size
