Week 4 Flashcards
(59 cards)
What is the course of the disease?
Cause (smoking, etc) -> abnormality -> Diagnosis -> prognosis -> treatment -> prevention -> health services
Once diagnosed its clinical stage
Outcome stage is after treatment
What’s the difference between pre-clinical and clinical stage?
Pre-clinical = Biologic onset of disease and symptoms first appear
Clinical = symptoms first appear, disease diagnosed, treatment, outcome
How to identify the onset of the disease?
With technology but usually hard to do which is why patients develop symptoms and then go to hospital
What is Prognosis?
- Prediction of future course of treated disease.
- Includes underlying natural history of disease being studied.
- Includes factors extrinsic to natural history (hypertension in heart attack, presence of other disease) of disease being studied.
- Includes thinking about the spectrum of disease.
- Usually thought of as domain of cohort study (to study different outcomes at different stages of the disease)
Clinical focus is on what?
recognition of disease.
Signs and symptoms lead usual diagnosis of disease.
Retrospectively, we often recognize clinical premonitory signs and symptoms, and that disease is probably clinically present though not diagnosed.
T or F: Diseases is usually present before presence of signs/symptoms.
True
What is Detection threshold (DT)?
Earliest time at which the disease can be detected by screening using available means. (ex: blood work, etc)
Defines a detectable pre-clinical phase if prior to clinical undiagnosed.
What is Therapeutic threshold (TT)?
Last time at which medical intervention has an important effect (usually curative) on altering the natural history of the disease
Longer detectable pre-clinical phase and therapeutic threshold late in natural history define a condition as….
amenable to screening.
- DT changes with progression of diagnostic modalities.
- TT is often empirically determined (Assumed early treatment works)
Chat says:
1. Longer Detectable Pre-Clinical Phase (DPCP):
A disease with a longer period where it can be detected before symptoms appear is more suitable for screening.
This allows enough time to intervene before it progresses too far.
- Therapeutic Threshold (TT) Late in Natural History:
If effective treatment is still possible later in the disease process, it supports screening efforts.
This means that even if a disease is caught at a later stage, treatment can still be beneficial.
T or F: Ideally we want to detect disease as soon as possible?
True, the faster the TT is in the preclinical stage the better
T of F: Predicting factors can alter onset of disease
True
Usually thought of as domain of case-control research.
When we look at they’re environment and risk factors we can ‘‘predict’’ what disease they could develop
Risk factors for Depression: Female, Alcoholism, Stress,
Physical comorbidities, Being poor, genetics,
Risk factors for Dementia: Female Aged, Alcoholism, Stress, Physical comorbidities, Cognitive decline
Depression can be a prognostic risk factor for dementia
What is the difference between Prognostic vs. risk factor?
Is acute hypertension a disease?
Risk factor: Aged, Overweight, Smoking, Salty diet, Alcoholism, Stress
Prognostic factor: Aged, Overweight, Smoking, Salty diet, Alcoholism, Hypertension, Stress, Diabetes
The outcome will be a heart attack
Chat says:
The key difference between a prognostic factor and a risk factor lies in when they influence the disease process:
Risk Factor (Before Disease Development):
A characteristic or exposure that increases the likelihood of developing a disease.
Present before disease onset.
Example: Smoking is a risk factor for lung cancer.
Prognostic Factor (After Disease Diagnosis):
A characteristic that affects the outcome of a disease after it has already developed.
Helps predict disease progression, survival, or response to treatment.
Example: Tumor stage is a prognostic factor for cancer survival—patients with early-stage tumors have better outcomes than those with late-stage tumors.
Summary:
Risk factors help predict who will get a disease.
Prognostic factors help predict how the disease will progress once it is diagnosed.
What are the caracteristics of a Prognostic study?
After disease occurs:
Patient sample
- Clarify characteristics of cohort (severity, etc)
T0/Time zero or baseline
- Address the inception, or status of disease (incident patient - first time cancer patient)
Follow-up
- Make sure the time is long enough for the onset of event. (for ex: work with hospital data base for the témoins)
Outcomes of diseases
- Document all the possible events not just death or disease. (different caracteristics of the disease, chronic outcome, etc) (the # of deaths is your outcome)
How to Describe prognosis?
Summarize the course of disease by a single rate;
- Convey a limited information by a single rate;
- Communicate with survival curve, survival analysis.
How to Evaluation prognosis?
- Case-fatality
- 5-year survival
- Observed survival
- Median survival time
- Relative survival
What is case-fatality?
The number of people who die of a disease divided by the number of people who have the disease
commonly used for short-term, acute diseases
What is the difference between Case-fatality vs. mortality rate (which includes both persons with and without the disease interested)
Case-fatality: only prognostic cohort
Mortality: general population
Why is the person-time test not good?
Not all disease have same deterioration rate
The first 6 months are the most challenging. When they over come those 6 months, they are good to live for a couple years
Stage 4 cancer = people die in less than 6 months
Diabetes = people can still live for a long time
Thats why person-time study is not good to use to compare diseases?
What is the lead time biais?
It’s when 2 populations die at the same time from the disease but one got diagnosed before the other
Slide 18
What are things we ask during prognosis?
What is the fraction of a population which will survive past a certain time?
Of those that survive, at what rate will they die?
Can multiple causes of death or failure be taken into account?
How do particular circumstances or characteristics increase or decrease the odds of survival?
What is survival analysis?
A study of the occurrence and timing of events. Covariates are studied to determine their effect(s) on survival duration. Although applicable for both retrospective and prospective data, they are best for the latter
Which Two features of survival analysis are not found in conventional statistics?
- censoring (you get some info but not all of it)
- time-dependent covariates (time-varying explanatory variables)
What does survival analysis analyse or look at?
Analyze survival data derived from laboratory studies of animals, clinical and epidemiological studies of humans, and other applications;
Predict the probability of response, survival, or mean lifetime;
Compare the survival distributions of experimental animals or human patients;
Identify risk and/ or prognostic factors related to event, survival, and the development of a disease.
What are Key elements of survival analysis?
Survival time
- The time to the occurrence of a given event. (time of diagnosis to time of death)
Censor
- Some patients may be alive or event-free at the end of the study period, or loss follow-up. The exact survival times of these subjects are known. (you have half the image but not clear. Ex: Some people are still alive after the 5-year follow window. You don’t know what happens to them after that.
Ex: people leave your study half-way through, you have no info on if they’re alive or not after they leave)
Event
- This event can be the development of another disease, response to a treatment, relapse, or death.
