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Clinical Preventive Medicine

Clinical Preventive Medicine. Wang Min ( 王敏) School of Public health and general medicine. Clinical Preventive Medicine ( CPM )

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Clinical Preventive Medicine

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  1. Clinical Preventive Medicine Wang Min(王敏) School of Public health and general medicine

  2. Clinical Preventive Medicine (CPM) • those personal health services provided in the context of clinical medicine, the purpose of which is to maintain health and reduce the risk of disease and untimely disease.

  3. Preventive services were divided into three categories • Screening tests(筛检) • Counseling interventions(健康咨询) and health education(健康教育) • The Periodic Health Examination(周期性健康检查) • Nutrition guidance(营养指导) • Immunizations (免疫预防) • Chemoprophylaxis(化学预防)

  4. Screening • Screening is a public health service in which members of a defined population, who do not necessarily perceive they are at risk of, or are already affected by a disease or its complications, are asked a question or offered a test, to identify those individuals who are more likely to be helped than harmed by further tests or treatment to reduce the risk of a disease or its complications.

  5. The Purpose of Screening: • to find persons with risk factors in which preventive interventions could be used or to identify individual with early or asymptomatic treatable disease.

  6. The principle of screening test: 1.The disease should be an important health problem, having severe consequences or high prevalence 2. The detection of rare diseases may lead to high cost-benefit ratios. 3.The epidemiology and natural history of the condition, including development from latent to declared disease, should be adequately understood and there should be a detectable risk factor, disease marker, latent period or early symptomatic stage. 4.An effective preventive intervention or treatment should be available. 5.All the cost-effective primary prevention interventions should have been implemented as far as possible.

  7. The test 1.There should be a simple, safe, precise and validated test. 2.The distribution of the test values in the target population should be known and a suitable cut-off level defined. 3.The test should be acceptable to the population 4.There should be an agreed policy on the further diagnostic investigation of individuals with a positive test result and on the choices available to those individuals.

  8. The treatment • 1.There should be an effective treatment or intervention for patients identified through early detection, with evidence of early treatment leading to better outcomes than late treatment. • 2.There should be agreed evidence-based policies covering which individuals should be offered treatment and the appropriate treatment to be offered. • 3.Clinical management of the condition and patient outcomes should be optimised by all health care providers prior to participation in a screening programme.

  9. screening test must satisfy two major requirements to be considered effective: 1The test must be able to detect the target condition earlier than without screening and with sufficient accuracy to avoid producing large numbers of false-positive and false-negative results (accuracy of screening test ). 2 Screening for and treating persons with early disease should improve the likelihood of favorable health outcomes (e.g., reduced disease-specific morbidity or mortality) compared to treating patients when they present with signs or symptoms of the disease (effectiveness of early detection ).

  10. Pros and cons of screening

  11. Counseling interventions • are those in which the patient receives information and advice regarding personal behaviors (e.g., diet) that could reduce the risk of subsequent illness or injury. The Task Force did not consider counseling that addresses the health-related behaviors of persons who have already developed signs and symptoms of the target condition.

  12. Counseling interventions and health education 1. Use plain language. 2.Start with the most important information first. 3.Use repetition to reinforce your message. 4.Ask the patient to restate the message. 5.Provide an opportunity for questions.

  13. Counseling/Education about Disease • • Be specific and concrete. • • Start with the most important information first. • • Use repetition to reinforce your message. • • Ask the patient to restate the message. • • Provide opportunities for questions.

  14. What Works? • • Provide information • – Use multiple forms of information. • – Answer questions. • • Reward patients for positive behavioral • change. • • Tailor the intervention to the patient’s • needs. • • Provide feedback about the change in • health status measure.

  15. Example • What is Hypertension? • Why does hypertension need to be treated? • How is hypertension treated? • Managing and Preventing Hypertension • • BMI 18.5 – 24.9 kg/m2

  16. Exercise • – 30 minutes per day most days of week • “Moderate” alcohol consumption • – Men 2 drinks or fewer per day • – Women 1 drink or fewer • • Increase dietary intake potassium • – 3500 mg a day • • Increase dietary intake potassium • – 3500 mg a day

  17. Periodic Health Examinations(RPHE:周期性健康体检) • History • RPHE developed with consideration of overall financial impact and patient considerations • Specific costs not calculated • specific patient considerations not elicited but board members served as surrogates

  18. The RPHE “These recommendations are provided only as assistance for physicians making clinical decisions regarding the care of patients.” “Can not substitue for the individual judgement brought to each clinical situation by the patient’s family physician.”

  19. AAFP Recommendations • SR Strongly Recommend: Good quality evidence exists which demonstrates substantial net benefit over harm; the intervention is perceived to be cost effective and acceptable to nearly all patients • R Recommend: Although evidence exists which demonstrates net benefit, either the benefit is only moderate in magnitude or the evidence supporting a substantial benefit is only fair. The intervention is perceived to be cost effective and acceptable to most patients.

  20. AAFP Recommendations • NR No Recommendation Either for or Against: Either good or fair evidence exists of at least a small net benefit. Cost-effectiveness may not be known or patients may be divided about acceptability of the intervention. • RA Recommend Against: Good or fair evidence which demonstrates no net benefit over harm.

  21. AAFP Recommendations • I Insufficient Evidence to Recommend Either for or Against: No evidence of even fair quality exists or the existing evidence is conflicting. • I-HBHealthy Behavior is identified as desirable but the effectiveness of physician’s advice and counseling is uncertain.

  22. Health Examination Process Process: - planning - implementation - health education - recommendat-ions Definition of needs Results Evaluation 8

  23. Example

  24. Immunization

  25. Terms • Immunization – conferring immunity by artificial means • Vaccination – conferring immunity to a disease using a vaccine or special antigenic material to stimulate the formation of appropriate antibodies • Vaccine – preparation of antigenic material – stimulates Ab production – confers active immunity vs.disease • Latin “vacca” = cow (from cowpox)

  26. Immunization Using vaccines or antibody-containing preparations to provide immune protection vs. specific diseases • Passive • Preformed antibodies - another host • Protect individual exposed to disease • Active (vaccines) • Modified / purified pathogens or their products • Stimulate host to produce own specific immunity

  27. Passive Immunization • IgG - immediate protection - no memory • Standard Igs (human, animals) Non-specific • Pooled plasma from donors • Igs vs. many common viruses • Human hyperimmune serum (high titre) Specific • From donor c. high titre Abs to specific virus • Against specific (single) virus

  28. Passive Immunization Indications: • Exposure has occurred, or is expected to occur soon • No effective vaccine exists or time req’d too short • Underlying illness – prevents admin. vaccine E.g. uses: • Standard Ig – Congenit./acq. Ig deficiency, prevent Hep A • Rabies Ig (HRIg) – post-exposure prophylaxis • VZ Ig – post-exposure prophylaxis if at high risk • CMV Ig – passive imm. renal transplant recipient

  29. Vaccines - Active • Injection of viable / non-viable pathogens or purified pathogen products • Response as if being attacked by intact organism • Live / inactivated / DNA vaccines • Effective starting after ~2 wks to few months • Prolonged immunity <-- own antibodies produced

  30. Active vaccine - Live attenuated pathogens • Multiplies inside human host & provides strong antigenic stimulation • Provides prolonged immunity (yrs to life), often with single dose • Vaccine often provides cell-meditated immunity • Disadvantage – can revert to virulent form --> Do not give to immunocomprom., pregnant

  31. Active - Killed micro-organism • Does not multiply in human host • Immune response depends on Ag content of vaccine • Multiple doses of vaccine required with subsequent booster doses • Provides little cell-mediated immunity • No possibility of a vaccine-assoc. infection

  32. Active - Microbial extracts • Extracted molecules (Ags): • from pathogen • from acellular (non-infectious) filtrate of culture medium in which org. grown • recombinant DNA techniques • Vaccines can be prepared with toxoids (=derivatives of exotoxins) • Used when pathogenicity of org. is due to secreted toxin • E.g., tetanus, diphtheria

  33. Active - Toxoids • Derivatives of bacterial exotoxins • Rendered non-toxic • But remain immunogenic • Admin – IM, SC • E.g. • Tetanus • Diphtheria

  34. Vaccine components

  35. Age & Immunity • Passive immunity from mother • Maternal IgG passes the placenta • Before and at birth – IgG present • Breast milk – secretory Abs (GI & resp. tract) • Active Immunization • Infant begins to produce Abs in 1st yr • Start immunization at 2 months (usually) • Elderly --> weaker immune response

  36. Problems with vaccines • Localized - at site of injection • Anaphylaxis to Ag or non-microbial content vaccine (eggs) • Contamination with pathogen • Reversion of attenuation • Lack of efficacy if another concurrent infection (rubella & polio vaccine) • Organisms with lots of serotypes

  37. Vaccine development Properties of good candidate: • Organism – causes significant illness • Organism – 1 serotype • Organism – no oncogenic potential • Antibodies – block infection / systemic spread • Vaccine – heat stable

  38. Success of immunization program • Composition of vaccine • Life-long immunity • Administration • Timing • Site • Conditions

  39. Immunization - ? When • Birth - Hep B • Childhood - DTP, Polio, Hep B (2,4,6/12), Hib (2,4,12), MMR (12/12), DT (15 -19yrs) • Adult - Boosters, 50yrs – DT (unless booster <10 yrs) • Travellers - Yellow fever, Typhoid • Non-immune ♀ - MMR • Risky lifestyle - Hep B, Heb A • Aboriginal & >50yrs – Influenza (yearly), or non-Abor & > 65 yrs - Pneumococcus (5-yearly)

  40. Standard vaccination schedule For footnotes, see: http://www.dh.sa.gov.au/pehs/Immunisation/aust-vacc-schedule-web.pdf From: http://www.dh.sa.gov.au/pehs/communicable-diseases-index.htm

  41. Recommended Childhood and Adolescent Immunization Schedule

  42. Other target groups From: Vaccine brochure, SmithKline Beecham

  43. Challenges • Predicting the protective ags • e.g., Influenza (haemagglutinin & neuraminidase variants) • Not knowing the virulence determinants • e.g., Tuberculosis • Antigenic variation • Promoting T-cell stimulation

  44. Vaccine Safety – New Challenges… 1.More vaccines to oversee 2.Investment not kept up with • demands 3.Benefits “invisible” as diseases disappear 4.Real and perceived risks of • vaccine more apparent 5.Public trust at stake

  45. Chemoprophylaxis • Chemoprophylaxis as primary prevention refers to the use of drugs or biologics taken by asymptomatic persons to reduce the risk of developing a disease.

  46. The use of chemoprophylaxis is limited primarily by two factors: 1.All medications have the potential to cause side effects. In general, chemoprophylaxis should be initiated only when the benefits of treatment outweigh the risks. 2.The cost associated with chemoprophylaxis may be prohibitive, particularly when the cost of treatment is high or the incidence of the target disease is low. Many forms of chemoprophylaxis are therefore not cost-effective.

  47. Thank you!

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