An Ounce of Prevention

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An Ounce of Prevention

• Duke Family Medicine
• Common Problems in Primary Care

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Opportunity knocks

• You are starting a new job in your hometown and
  the senior partners of the group ask you to set
  up a prevention protocol for the practice.
• A 16-year old student from the high school track
  team with a stated purpose of sports physical
  is your next patient.
• A couple presents for a pre-marital blood test
  with state form in hand.
• You have been asked to be on the committee for a
  local community health fair.
• You are seeing an 11-month-old for his third ear
  infection.
• Your first patient of the afternoon has a family
  history of breast cancer and she is starting to
  notice hot flashes and missing periods.
• The local paper has an article about the death of
  a local teenager in a corn silo.
• There is a new shirt factory in town and several
  of your patients are joining the work force
  there.

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What we will cover

• Principles of prevention
• Primary prevention
• Secondary
• Screening
• Benefits Risks of Screening
• Sensitivity, Specificity of a test
• Positive Predictive Value of a test
• How prevalence effects Prediction
• Shared decision making
• Counseling

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Purpose

• Reduce incidence of disease
• Example Immunization
• Reduce mortality and morbidity of disease by
  early detection
• Modifying personal behavior
• Knowledge as power

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Start at the beginning

• Risk profile
• Family history
• Age
• Gender
• Ethnic origin
• Exposures
• Lifestyle
• Targeted prevention
• Population profile

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Opportunity Knocks

• Are you answering the door?

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Family Hx

• What 6 target adult diseases should be
  highlighted in family history?

• Heart disease
• Diabetes
• Stroke
• Breast cancer
• Ovarian cancer
• Colon cancer

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Strategies

• Primary
• Prevention of disease occurrence
• Secondary
• Screening asymptomatic population for risk
• Preclinical
• Tertiary
• Treatment of symptomatic population
• Minimize complications

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Prevention Components

• Screening
• Test or standardized exam
• Immunizations
• Chemoprevention
• Drugs or biologicals to prevent disease
• Counseling

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Does it work?

• Stroke mortality down 50 since 1972
• Early detection and treatment HTN
• Cervical cancer mortality reduced by 80
• Neonatal screening
• Reduction in cognitive dysfunction
• PKU
• Congenital hypothyroidism

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Primary Prevention

• Immunizations

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Chemoprophylaxis

• ASA for adults at high risk for CAD
• A Recommendation
• Benefit gt risk
• Tamoxifen or raloxifene for breast cancer
• No in average or low risk
• Counseling and shared decision making in high
  risk

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Chemoprophylaxis

• Post-exposure prophylaxis
• H. influenza, B
• Hepatitis A
• Hepatitis B
• Meningococcus
• Rabies
• Tetanus

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Chemoprophylaxis

• Hormone replacement
• Patient preference
• Risk gt benefit
• Individual risk assessment
• I recommendation
• Travel
• Malaria prophylaxis
• Yellow fever

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Screening

• Secondary prevention

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Criteria for effective screening

• The burden of illness is high
• Detection is possible before symptoms are evident
• Treatment is available, acceptable reduces
  morbidity and mortality if applied early
• Benefits of treatment outweigh harm including
  discomfort anxiety
• First, do no harm

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Recipe for success

• Test is accessible
• Test is acceptable to patient
• Patient willing to participate in follow-up and
  treatment
• Cost effective

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Natural History of Disease

• ? ? ?
• 1 ? ?2 ? ?3 ?? 4

1. Biological onset
2. Early diagnosis possible
3. Usual clinical diagnosis
4. Outcome

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Natural history of disease

• Critical point

Biological onset
Symptomatic onset
Outcome
Screening
Case Finding
Critical point therapy effective prior to this
point in natural history of disease, ineffective
afterwards
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Critical point and screening

• Identify the disease/s illustrates a critical
  point suitable to screening
• Colorectal cancer
• Cervical cancer
• Pancreatic cancer

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Critical point

• Cervical cancer
• Critical point occurs prior to onset of symptoms
• Effective intervention available in asymptomatic
  phase
• Intervention improves outcome
• Colorectal cancer
• Pancreatic cancer
• Aggressive
• Short history

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Screening bias

• Lead-time bias
• Length bias

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Screening advances time of diagnosis, not
survival time
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50 detected by screening while remainder
progress to clinical symptoms during screening
interval
False Security
Longer asymptomatic period, more likely to be
detected in screening interval
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Screening guidelines

• USPSTF
• Review evidence of effectiveness for screening in
  asymptomatic, average risk population
• Make recommendations for clinical preventive
  services
• Identify research agenda for clinical prevention

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Organizations

• USPSTF
• Evidence based
• Specialty organizations
• AAFP
• ACP
• ACPM
• Etc.

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USPSTF Ratings Evidence

• Strongly recommends that clinicians provide the
  service to eligible patients. (Good evidence)
• Provide this service to eligible patients.
  (Fair evidence)
• No recommendation for or against routine
  provision of the service. (Fair evidence, Close
  balance)
• Recommends against routinely providing the
  service to asymptomatic patients. (Ineffective
  or risk gt benefit)
• Evidence is insufficient to recommend for or
  against routinely providing the service.
  (Evidence lacking or poor quality or conflicting,
  cannot determine risk benefit ratio)

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Quality of Evidence

• Good Evidence includes consistent results from
  well-designed, well-conducted studies in
  representative populations that directly assess
  effects on health outcomes.
• Fair Evidence is sufficient to determine effects
  on health outcomes, but the strength of the
  evidence is limited by the number, quality, or
  consistency of the individual studies,
  generalizability to routine practice, or indirect
  nature of the evidence on health outcomes.
• Poor Evidence is insufficient to assess the
  effects on health outcomes because of limited
  number or power of studies, important flaws in
  their design or conduct, gaps in the chain of
  evidence, or lack of information on important
  health outcomes.

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Example Diabetes

• USPSTF
• Screening does detect in pre-symptomatic phase
• No early intervention evidence (I)
• Screening approved for hypertension and
  hyperlipidemia patients (B)
• Modifies management
• The Critical Point

• ADA
• Start age 45
• FPG
• In a health care setting
• Every 3 years
• Earlier and more frequent if BMI gt 25 with
  additional risk factors
• E recommendation

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How to judge a Screening Test

• Sensitivity
• In asymptomatic phase
• Specificity
• Avoid false positives
• Positive Predictive Value (PPV)
• When yes means yes
• Negative Predictive Value (NPV)

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Indices of accuracy

• Sensitivity
• Proportion with disease who correctly test
• Low proportion of false-negatives
• Specificity
• Proportion without disease who correctly test
• Low proportion of false-positives
• Gold standard
• Sensitivity and Specificity describe test
  accuracy and areindependent of disease prevalence

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Accuracy

• Sensitivity
• a/ac
• Specificity
• d/bd
• PPV
• a/ab
• NPV
• d/cd

Condition Present Condition Absent
Positive Test a (True ) b (False )
Negative test c (False -) d (True -)
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Risks

• List potential risks of a poorly sensitive test
• False negatives
• List the potential risks of a poorly specific
  test
• False positives

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The potential for harm is real
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Accuracy

• Sensitivity
• a/ac
• Specificity
• d/bd
• PPV
• a/ab
• NPV
• d/cd

Condition Present Condition Absent
Positive Test a (True ) b (False )
Negative test c (False -) d (True -)
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Prevalence
The total number of cases of a disease in a given
population at a specific time.
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Predictive Value

• Given a positive results, what is the probability
  that disease is present?
• Positive Predictive Value (PPV)
• Proportion who test have disease
• Dependent on disease prevalence in the population
  studied.

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Prevalence and PPV
90 Sensitivity, 95 Specificity
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Size of population 100,000 Sensitivity of test 90 Specificity of test 90 Size of population 100,000 Sensitivity of test 90 Specificity of test 90 Size of population 100,000 Sensitivity of test 90 Specificity of test 90 Size of population 100,000 Sensitivity of test 90 Specificity of test 90 Size of population 100,000 Sensitivity of test 90 Specificity of test 90 Size of population 100,000 Sensitivity of test 90 Specificity of test 90
Cancer Prevalence 1 Cancer Prevalence0.1 Prevalence Cancer Prevalence 1 Cancer Prevalence0.1 Prevalence Cancer Prevalence 1 Cancer Prevalence0.1 Prevalence Cancer Prevalence 1 Cancer Prevalence0.1 Prevalence Cancer Prevalence 1 Cancer Prevalence0.1 Prevalence Cancer Prevalence 1 Cancer Prevalence0.1 Prevalence
Cancer Present Cancer Absent Cancer Present Cancer Absent
Positive test 900 9,900 Positive test 90 9,900
Negative test 100 89,100 Negative test 10 89,910
PPV 8.3 PPV 8.3 PPV 0.9 PPV 0.9
12 worried for every case 12 worried for every case 111 worried for every case 111 worried for every case


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Reliability

• Reproducible results
• Valid
• Reliable

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A Clinical Question

• A 30 y.o. woman presents to your office for a
  check-up. She has no history of illness.
• What preventive measures would you recommend on
  the basis of age and sex alone?
• What data do you need to decide about additional
  screening?

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Routine recommendations

• Alcohol Misuse
• ASA for prevention of CVD
• Blood pressure screening
• BCRA mutation screening
• Genetic risk assessment for ovarian and breast
  cancer susceptability
• Breast cancer prevention medication
• Cervical cancer screening

• Alcohol B
• ASA high risk
• BP screening A, 18 and older
• BCRA High risk
• Breast Ca prevention High risk
• Cervical cancer screening A, sexually active
  with a cervix

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30 y/o female

• Chlamydia screening
• Dental and periodontal disease
• Depression
• Diabetes
• Diet
• G.C.
• HIV

• Chlamydia A, through age 25 and high risk
• Dental B, dental care, flossing, fluoride, oral
  cavity exam
• Depression B, screening in appropriate setting
• Diabetes B, high risk HTN, Hyperlipidemia
• Diet Hyperlipidemia or other risk factors for
  chronic disease, B
• G.C. high risk, age lt 25
• HIV Risk based A

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30 y/o old female

• Lipids
• Obesity
• Syphilis
• Tobacco use

• Lipids high risk men age 35, women 45 treat if
  high and at increase risk for CHD younger if
  risk high (20-30 men, 20-45 women)
• Obesity B, offer intensive counseling and
  behavioral interventions.
• Syphilis A for high risk
• Tobacco A, screen and offer intervention
• TB screening high risk

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Level D
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But, doc!

• Shouldnt I have a mammogram?
• Second leading cause of cancer death in US women
• 1/8.2 women in US diagnosed over lifetime
• 1/30 will die because of the disease
• gt 50 without identified risk factors

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Cases of Breast Cancer in 2000
ACS Surveillance Research, 2000
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Breast Cancer

• Prevalence Varies by Age
• 20 cases/100,000 women _at_ age 30
• 180 cases/100,000 women _at_ age 50
• Risk Factors
• Age, Genetic, Hormones, Radiation, Prior Cancer,
  High Fat Diet, Alcohol

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Cumulative Risk of Breast CA
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Mammogram _at_ age 30
Prevalence 20/100000 Sensitivity
70 Specificity 95 PPV 0.003
For every case, 358 undergo needless evaluation,
cost and anxiety 5013/14358
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Mammogram _at_ age 60
Prevalence 180/100000 Same sensitivity and
specificity PPV 0.026
For every case, 39 get worked up needlessly
5119/128
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What about outcomes?
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Outcome Risk reduction

• Relative risk and RR reduction
• Probability of event in active group/probability
  in control group
• RR reduction
• Absolute risk/ probability in control group

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Screening effectiveness

• Gain in life expectancy
• Cost per case detected
• Cost per life saved
• Gain in quality-adjusted years
• Number needed to screen
• How many need to be screen impact one person

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Mammography

• Does screening reduce disease?

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For Breast Cancer

• The burden of illness is high
• Most common CA in women with 182,000 new cases
  44,000 deaths in 2000
• Detection is possible before symptoms
• Self Exam, Physician Exam, Mammogram
• Treatment is available
• Surgery, Chemotherapy, Radiation
• Treatment value exceeds the discomfort anxiety

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Mammography Benefit

• Swedish study
• 4 randomized studies
• 247,010 women
• 15.8 years follow-up
• 21 reduction in mortality
• RR 0.79 in screened group
• Statistically significant in 55-69 y/o
• Benefit evident at 4 years out
• Increased to 10 years
• 20-30 reduction in mortality realized after a
  delay of 6-10 years

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USPSTF

• 2002 USPSTF recommendations
• No evidence of value for ages lt40
• Strongest evidence age 50-69
• Every 1-2 years beginning at age 40
• Most studies indicate mortality benefit
• Absolute benefit smaller in 40s due to
  incidence in the age group vs. gt50
• No proof of value gt 70 but likely is a good idea
• In absence of co-morbidities that reduce life
  expectancy

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What if she were a he?

• Alcohol Misuse
• ASA for prevention of CVD
• Blood pressure screening
• Chlamydia screening
• Dental and periodontal disease
• Depression

• Diabetes
• Diet
• G.C.
• HIV
• Lipids
• Obesity
• Syphilis
• Tobacco use

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He?
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When you get older
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Older
The younger woman was D.
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Older
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Older
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Colorectal cancer

• Long latency 10 years
• Large Adenomatous Polyps
• Risk assessment
• Fecal Occult Blood Test for Colon Cancer
• Sensitivity 26-92
• Specificity 90-99
• PPV 2-11
• Sigmoidoscopy
• 50 reduction in overall CRC mortality
• Colonoscopy
• Awaiting data on outcome comparison

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Shared decision making

• Serum PSA for Prostate Cancer
• Sensitivity and Specificity
• Varies with cutoff value, age and comorbidity
• PPV 20
• 2nd leading cause of CA death in men
• Does screening improve outcome?

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Food for thought
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Shared decisions
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Shared decisions

• Would you feel better knowing?
• Not knowing?
• What happens if the PSA is elevated?
• What happens if you have cancer?
• What difference will it make for you to know?

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Shared decisions
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Shared decisions pros and cons
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Guidelines

• USPSTF
• Recommendation level I
• Major medical organizations
• Discuss potential benefits and possible harms
• Consider patient preferences.
• Individualize the decision to screen.
• No endorsement of universal screening

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Selective screening

• Most likely to benefit
• Age over 50
• Younger men at high risk (45)
• African American men
• Younger age of onset
• More aggressive disease
• First-degree relative
• Unlikely to benefit
• Men with less than 10 year life expectancy

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Knowledge as power

• Family history
• CHD
• Risk increase x 2-6
• Cancer
• Colon 2-5 x increase
• Breast 2-6 x increase
• Prostate
• Nature vs. nurture
• Targeted screening ?
• Targeted intervention
• BEHAVIOR CHANGE?

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Motivation

• Identify stage of change
• Tailor made messages
• Patient preference
• Consider
• Knowledge and literacy
• Beliefs
• Culture
• Support
• Reflective listening

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Resources

• www.myhq.com
• ID pickens
• Password marshall
• USPSTF
• The Bible of prevention
• Asymptomatic population
• Office based
• Primary and secondary prevention
• Evidence based
• http//fmclerkship.mc.duke.edu

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Primum non nocere

• FINIS

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Five Rs

• Relevance
• Risks
• Rewards
• Roadblocks
• Repetition

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Behavioral counseling

• Assess
• Advice
• Agree
• Assist
• Arrange

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Encourage self-management

• Realistic goals
• Education
• Support
• Write it down
• Gold star treatment