Term
| What are the three levels of prevention? give an example of each. |
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Definition
-primary (pre pathogenesis, health promotion and specific protection against dz: immunization, sanitation, education, media campaigns, warning labels)
-secondary (pathogenesis phase, reduce progress of dz: cancer screening: CA already there and we want to detect it before clinical symptoms arise in order to improve prognosis)
-tertiary (halting disability from dz: PT) |
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Term
| What is the definition of screening? |
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Definition
-an examination of a group of asymptomatic people to detect those with a high probability of having a given dz, typically in a community setting
-the presumptive identification of unrecognized disease by the application of tests, exams, or other procedures that can be applied rapidly |
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Term
| What happens if you get a positive result from a screening test? |
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Definition
| followed up by diagnostic tests to confirm actual dz |
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Term
| If a woman comes in with a great lump and the doc sends her for a mammogram, is the mammogram a screening tool? |
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Definition
| No, it is no longer a screening tool and is now diagnostic bc she came in with the symptoms |
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Term
| What is the "who, what, and why" for screening? |
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Definition
Who: population of healthy people who are asymptomatic
What: Important health problem
Why: Early treatment favorably influences prognosis |
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Term
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Definition
-screening on a large scale of total population groups regardless of risk status
-Ex: everyone that goes to the doctor gets weight, height, BP etc |
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Term
| What is selective screening? |
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Definition
-screen subsets of the population at high risk for disease
-known prostitute comes in for an abscess tooth, but bc of her job you want to get some STI screenings. She is asymptomatic, but she is at HIGH RISK for STD's) |
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Term
| If someone comes into the clinic with known HTN, is the BP measurement a screening tool? |
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Definition
| No, it is now diagnostic because they knew they had HTN prior to coming to the clinic. |
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Term
| What are the three main decision makers when it comes to screening or not? |
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Definition
-important health problem with known natural hx
-suitable screening test and prevention methods
-available tx |
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Term
| What are three reasons that we should only screen dz's that are important health problems with known natural hx? |
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Definition
*identification early in pathogenesis
*recognizable latent stage
*prevalence is relatively high
-you want to screen for dz's for which you know the natural hx of dz, this way you know if it is worth screening. Prevalence should be high bc if the prevalence is low and you screen for it you end up getting more false tests than true tests. What is high depends on the importance of the dz |
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Term
| Why do we only want to screen for dz's which we have a suitable screening test and prevention methods? (3) |
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Definition
*effective methods available
*favorable cost-benefit ratio
*public acceptance must be high
-Ex: chlamydia tests in men are most often done by a swab test. Most men do not way to do this, they would pick to pee in a cup over the swab. Peeing in a cup is more expensive, but more people will get it and more providers will want to do it (public acceptance-- higher).... BUT if it's 100x more expensive to pee in a cup the norm will not be switched to that from swabbing. Must be taken into account that most is from tax payer dollars) |
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Term
| What are 3 reasons we should only screen for dz's for which there is available treatment? |
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Definition
-effective intervention will be available
-it has an impact on prognosis
-public acceptance must be high
*If there is no treatment, why would we screen? |
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Term
| What are the 5 characteristics of a good screening test? |
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Definition
1. simple (easy to learn and perform)
2. rapid (quick to administer; results available rapidly)
3. inexpensive (good cost-benefit ratio)
4. safe (no harm to participants)
5. acceptable (to target group) |
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Term
| A sexually active, monogamous 34yo woman has had 3 annual pap smears that show no abnormalities. According to the American College of Obstetricians and Gynecologists, the recommended interval for a pap smear in this woman is how many months? |
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Definition
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Term
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Definition
| (precision) consistency among repeated measures. Based on how well the test does in use over time- in its repeatability |
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Term
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Definition
| (accuracy) ability to measure the true value. Shown by how well the test actually measures what it is supposed to measure |
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Term
| Is it possible for a measure to be highly reliable but invalid? How about for a measure to be valid but unreliable? |
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Definition
-yes (a scale tells me I weigh 100 lbs every time I get on it (its reliable) but it is not valid since i do not weigh 100 lbs)
-no |
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Term
Two automated blood cell counters are tested twice using a prepared suspension of leukocytes containing 8,000 cells/mm3. The cell counts by devise A are 8,400 cells/mm3 the first time and 8,350 cells/mm3 the second. Devise B’s counts are 8,200 and 7,850 cells/mm3, respectively.
-which devise gives counts with greater validity? reliability? |
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Definition
-B is closer to the true value
-A only has 50 cells different between the two readings |
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Term
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Definition
| -the ability of a test to identify correctly all screened individuals who actually have the dz |
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Term
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Definition
| the ability of the test to identify only non-diseased individuals who actually do not have the dz |
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Term
| What is predictive value (+)? |
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Definition
| the proportion of individuals screened positive by the test who actually have the dz |
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Term
| What is predictive value (-)? |
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Definition
| the proportion of individuals screened negative by the test who do not have the dz |
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Term
| If we have to choose between a pt getting a false positive or a false negative, which is preferable? |
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Definition
| false positive, we do not want someone walking around with the dz w/o being treated |
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Term
| What is the formula for sensitivity using true/false negatives/positives? |
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Definition
| Sensitivity= TP/ (TP + FN) |
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Term
| What is the formula for specificity using true/false negatives/positives? |
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Definition
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Term
| Using the 2x2 table on slide 26, what is the formula for sensitivity? |
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Definition
sensitivity= the ability of the disease to identify correctly all screened persons who have disease
=a/(a+c) |
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Term
| Using the 2x2 table on slide 26, what is the formula for specificity? |
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Definition
specificity= ability of test to identify only non diseased persons when no disease is present
=d/(b+d) |
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Term
| Using the 2x2 table on slide 26, what is the formula for predictive value positive (PVP)? |
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Definition
PVP= proportion of screened positive persons who have dz, % of true positives among those individuals with positive result from the test
=a/(a+b) |
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Term
| Using the 2x2 table on slide 26, what is the formula for predictive value negative (PVN)? |
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Definition
PVN=proportion of screened negative persons who have NO disease, % of non-diseases persons among those having negative results from the test
=d/(c+d) |
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Term
| Using the 2x2 table on slide 26, what is the formula for prevalence rate? |
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Definition
Prevalence rate= the proportion of persons with disease, the amount of dz that exists in a population
=(a+c)/(a+b+c+d) |
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Term
| Using the 2x2 table on slide 26, what is the formula for accuracy rate? |
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Definition
Accuracy rate= the proportion of persons with true test results, how valid is the test. % of true positives and true negatives among individuals with results from the test
=(a+d)/(a+b+c+d) |
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Term
| For rare conditions, screening results are most of the positive tests are _________ positives |
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Definition
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Term
| When the prevalence of a dz falls, which predictive value falls and which rises? |
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Definition
| -predictive value positive falls and predictive value negative rises |
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Term
| As the prevalence increases, which predictive value increases? |
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Definition
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Term
| What are the costs of false positives and false negatives? (2 each) |
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Definition
- False (+): unnecessary tests, and labeling (stigma associated with HIV, etc)
-False (-): care for advances dz, premature death or disability |
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Term
| To improve sensitivity, the cut point used to classify individuals as diseases should be moved farther which way? |
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Definition
| in the range of the non diseased (normals) |
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Term
| To improve specificity, the cut point should be moved farther which way? |
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Definition
| in the range typically associated with the disease |
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Term
| What are two ways to evaluate screening programs? |
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Definition
-randomized control trials (subjects receive either the new screening test or the gold standard)
-case-control studies (cases: fatal cases of the disease; controls: nonfatal cases of the disease; exposure: screening program) |
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Term
A 43yo man complains of 2 months of nocturia (2X), a sense of incomplete bladder emptying, weak stream, and a need to strain to begin urination. Which of the following is considered to be optional in the initial evaluation of this patient?
A. DRE
B. PSA
C. Serum Creatinine
D. Urinalysis |
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Definition
B. PSA (this is often used to follow CA once the baseline for the pt is known. He is 43 yo and too young for this, should be started at 50)
*the first thing we need to do is rule out urinary blockage, PSA does not need to be done initially
-do a serum creatinine to measure kidney function and make sure there is no blockage
-do a UA to figure out if the urinary tract is blocked
-DRE needs to be done... |
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Term
| What group conducts reviews and research evidence to create evidence based recommendations for preventive services that should be provided in the primary care setting? |
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Definition
| US Preventive Services Task Force (USPSTF) |
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Term
| What are the current recommendations for mammograms? |
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Definition
| routine screening for asymptomatic women in their 40's is not warranted and mammograms for women over 50 should be biennially |
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Term
| What is lead time bias in screening? |
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Definition
| perception that the screen-detected case has longer survival because the disease was identified earlier |
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Term
| What is length bias in screening? |
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Definition
-particularly relevant to CA screening
-tumors identified by screening are slower growing and have a better prognosis |
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Term
| what is selection bias in screening? |
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Definition
| -motivated participants have a different probability of dz than do those who refuse to participate |
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Term
| What are three dangers of breast CA screening warranting false positives for a relatively rare condition? |
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Definition
-cumulative effects of radiation from dozens of mammograms
-the invasiveness of biopsies (some of them minor operations)
-the aggressive and debilitating treatment of slow-growing tumors that would never prove fatal |
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