1. prevention
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3. To accomplish this, people without specific complaints undergo interventions to identify and modify risk factors, to avoid the onset of disease, or to find disease early in its course
The activity is referred to as preventive care or the periodic health examination
Preventive care constitutes a large portion of clinical practice. (1) physicians should understand the conceptual basis and content of the periodic health examination.
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4. Population and clinical prevention
Prevention at the community effective can be effective such as Immunization requirements for students, no-smoking regulations in public buildings
In smoking prevention efforts, clinicians help individual patients stop smoking and public education, regulations, and taxes prevent teenagers from starting to smoke
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5. Types of clinical prevention
Immunization : Childhood immunizations to prevent disease such as diphtheria, tetanus
Screening: Screening is the identification of asymptomatic disease or risk factors( Alpha-fetoprotein)
Behavioral counseling (lifestyle Changes) Clinicians can give effective behavioral counseling to motivate lifestyle changes, encouraging parents of a newborn to purchase an infant seat for the car
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6. Chemoprevention:is the use of drugs to prevent disease
Chemoprevention:is the use of drugs to prevent disease. For example, ocular antibiotic prophylaxis of all newborns to prevent gonococcal ophthalmia
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7. Levels of prevention Prevention as” To keep from happening”
Clinicians effects are aimed at preventing the occurrences of the five Ds: death, disease, disability, discomfort, dissatisfaction, and destitution
Depending on when in the course of disease interventions are made three levels of prevention are possible
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9. Primary Prevention
Primary prevention keeps disease from occurring at all by removing its causes
Primary prevention is often accomplished outside the health-care system at the community level
Primary prevention activities occur in specific occupational settings
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10. Secondary Prevention
Secondary Prevention detects early disease when it is asymptomatic and when treatment can stop it from progressing.( Pap smears)
Screening tests are part of many primary and all secondary prevention activities.
If the clinician is not committed to further investigation of abnormal results and treatment, if necessary, the screening test should not be performed at all
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11. Tertiary prevent
refers to those clinical activities that prevent further deterioration or reduce complications after a disease has declared itself
Well-performed tertiary prevention goes beyond treating the problems patients present with
There are few, if any, tertiary prevention programs outside the health-care system
it is particularly important in the management of patients having a fatal disease. The goal here is not high-quality time a patient has left
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12. Approach to clinical orevention
When considering what to do routinely for patients without specific symptoms for a given disease
The clinician Must first decide which medical problems Should try to prevent
Three criteria are important when deciding what condition to include in a periodic examination:
1-The burden of suffering caused by the condition
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13. 2-The quality of screening test if one is be performed.
3-The quality(effectiveness, safety, and cost) of the intervention for primary prevention or the effectiveness of treatment for secondary prevention after the condition is found through screening.
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15. Burden of suffering
Only conditions posing threats to life or health (the five Ds in chapter1)should be included in preventive care
A particular condition may cause great suffering for individuals But may occur too rarely-especially in the individual’s particular age group-for screening to be considered
A particularly Difficult dilemma is The situation in which a person is known to be at high risk for a condition,
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16. but the evidence regarding effectiveness of prevention is unclear
If the evidence is against effectiveness, they may hurt rather than help the patient by preventive activities
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17. Screening tests in preventive care
Screening tests are similar to diagnostic tests; often, the same test is used in both situations.
The difference between prevalence and incidence screens and three biases that can occur in screening studies: lead-time, length- time, and compliance biases
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18. Prevalence and incidence screens
The yield of screening decreases as screening is repeated over time.
The first time that screening is carried prevalence screen-cases of the medical condition will have been present for varying lengths of time.
Second Screening is called an incidence screen
This means that the positive predictive value for test result will decrease after the first round of screening
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20. Special biases in screening
The best way to establish the efficacy of treatment is with a randomized controlled trial. This is true for all interventions but especially for early treatment after screening
It takes years and requires large number of people to be studied
A clinical impression of the effect of screening simply does not suffice in this situation
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21. Lead-time bias
Lead time is the period of time between the detection of a medical condition by screening and when it ordinarily would be diagnosed because a patient experiences
The amount of lead time for a given disease depends on the biologic rate of it and how early the screening test can detect the disease
How can lead time cause biased results in a study of the efficacy of early treatment?
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23. screening would have been given not more survival time but more disease time
An appropriate method of analysis to avoid lead time bias is to study both a screened group of people and a control group of similar people who do not get screened, and compare age-specific mortality rate rather than survival rates
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25. Length-time bias
occurs Because the proportion of slow-growing lesions diagnosed during screening is greater than the proportion of those diagnosed during usual medical care
Length-time bias makes it seem that screening and early treatment are more effective than usual care
Mortality rates of cancers found through screening may be better than those not found through screening, but screening is not protective in this situation
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28. Compliance bias
Compliance bias is the result of the extent to which patients follow medical advice
If a study compares disease outcomes among volunteers with outcomes in a group of people who did not volunteer, better results not be the result of screening but rather factors related to high compliance.
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29. Biases due to length time and patient compliance can be avoided by Randomized trials Because patients who are randomly allocated fast-growing tumors on average, comparable levels of compliance
Because randomized controlled trials and prospective are difficult to conduct, take a long time, and are expensive, investigators sometime try to use other kinds of studies, such as cohort studies or case control studies
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31. Criteria for a good screening test
High sensitivity and specificity:
A good screening test must, therefore, have a high sensitivity, so that it does not miss the few cases of disease present also be sensitive early
A screening Test should also have a high specificity to reduce the number of people with false-positive results
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32. In screening the gold standard for the presence of disease is not only another test but also a period of follow-up. The gold standard test is routinely applied only to people with positive screening test result, to differentiate between true and false-positive result. A period of follow-up is applied to all people who have a negative screening test result, in order to differentiate between true and false-negative test result.
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33. If the
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34. detection and incidence methods for calculating sensitivity
Calculating sensitivity by counting cancers detected during screening as true positive and interval cancers as false negatives is as referred to as the detection method
There are two difficulties : first it requires that the appropriate amount of follow-up time for interval cancers be known.
second ; the detection method also assumes that the abnormalities detected by the screening test
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35. Would go on to cause trouble if left alone
the incidence in persons not undergoing screening and the interval cancer rate in persons who are screened
True sensitivity of a test is probably between the estimates of the two methods
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37. High positive predictive value
Because of the low prevalence of most disease
the positive predictive value of most screening low , even for tests with high specificity
Clinicians can minimize the problem by centrating their screening efforts on people with a higher prevalence for disease
Example: for breast cancer
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39. Simplicity and low cost
An ideal screening test should take only a few minutes to perform, require minimum preparation by the patient , depend on no special appointment , and be in expensive.
The financial ”cost ” of the test depends not only on the cost of the procedure itself it depends also:
1-on the cost of subsequent evaluations preformed on patients whit positive test result
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40. 2-sensitivity , specificity ,and predictive value affect cost
3-the test requires a specials visit to the physician
4- how often a test must be repeated
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41. Safety
It is reasonable and ethical to accept a certain risk for diagnostic tests applied to sick patient seeking help for specific complains
For example:colonoscopy
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42. Acceptable to patient and clinicicians
If a screening test is associated with discomfort , it usually takes several years to convince large percentage of patients to obtain the test
The acceptability of the test to clinicians is a criterion usually overlooked by all but ones performing it
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43. labeling
The psychological impact of a test is called a labeling effect.
A good screening test result produces either no labeling effect or a positive labeling effect
If being given a clean bill of health promotes a positive attitude toward one’s daily activities ,a positive labeling effect occurred
Screening might promote a sense of vulnerability instead of health.
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44. Possible adverse effects from screening
Adverse effects of screening tests include discomfort during the test procedure (like mammography) long-term radiation effect , false positive results and overdiagnosis
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45. Risk of false-positive result
Risk of false-positive result can lead to negative can lead to negative labeling effect , inconvenience ,and expense in obtaining follow up procedures.
This happen in two ways:
1-most clinicians do not perform only one or two tests on patients presenting for routine checkups
2-many people may experience a false-positive screening result is that most tests are repeated
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47. Risk of pseudodisease( overdiagnosis )in cancer screening
Some cancers are so slow-growiong,and some even regress , if such cancers are found through leading ,they are called pseudodisease
the process leading to their detection is called overdiagnosis because finding them does not help the patient.
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48. The challenge is to differentiate those early lesions that will go on to cause morbidity and mortality from those that will lie dormant throughhout life
It is necessary to determine disease-specific mortality rate and to compare a screened group with a similar unscreened group
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50. Effectiveness of treatment
The treatment can efficacious if able to produce a beneficial result in ideal situations and under usual conditions ,taking into account patient compliance
Cost –effectiveness analysis formalizes this approach for policy makers , estimating all costs related to disease occurrence that might be saved as well as prevention costs.
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51. efficacy and effectiveness are usually better documented for pharmaceutical than they are for behavioral counseling
Nevertheless health behaviors are the most important determinants of health in modern society
But counseling that does not work wastes time , costs money and may harm patients
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53. They should be both efficacious and effective
Treatment for secondary prevention are generally the same as treatment curative medicine.
They should be both efficacious and effective
If outcome in the two situations(early treatment in compare whit diagnosed in the usual course of events) is the same, screening is not necessary
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54. Current recommendations
1-abandoning routine annual checkups in favor of a selective approach in which the tests to be done depends on person’ sex , age..
They also have turned their attention to the selection process for deciding what medical conditions should be sought
The clinicians should discuss the pros and cons of procedure with the patient
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