1. Phase 2a public health

2. Phase 2a public health
Phase 2a Revision Session Hannah Jauncey and Claire Walker 24/04/17
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3. Incidence and prevalence
Incidence: number of new cases of a disease/ condition in a population per unit time (usually per year).
Prevalence: number of existing cases of a disease/ condition in a population at a given point in time.
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4. Stages of change model Anyone know what the * represents?
* Represents relapse which can happen at any stage.
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5. Prevention
Primary Prevention – Aims to prevent the onset of disease and involves interventions that are applied before any evidence of disease is present
Secondary Prevention – Detection of disease in earliest stages before symptoms are present and intervening to slow, stop or reverse disease progression
Tertiary Prevention – Interventions designed to arrest the progress of established disease and minimise its negative consequences.
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6. Bias
Bias – a systematic deviation from the true estimation of the association between exposure and outcome.
1. Selection Bias – systematic error in selection/allocation of study participants
2. Information (measurement) Bias – systematic error in measurement/classification of exposure or outcome.
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7. Screening:
A process which identifies apparently well individuals who may be at increased risk of developing a condition in the early stages of a condition so that intervention can alter the disease course → reduce morbidity and mortality.
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8. Examples of screening programs?
Bowel
Breast
Cervical cancer
AAA
Fetal anomaly screening programme (FASP)
Diabetic eye screening
Newborn and infant physical examination (NIPE)
Newborn heel prick test
Bowel: over every 2 years, faecal occult blood
Breast: aged (increasing to 47-73) every 3 years, mammo
Cervical cancer: over 25’s every 3 years, every 5 years, cervical smear liquid based cytology
AAA (men over 65)- USS
Fetal anomaly scans: at approx. 20 weeks
Diabetic eye screening- every year
NIPE within 72 hrs birth and between 6-8 weeks at GP
Newborn heelprick test at 5 days old
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9. Screening principles Important condition
Population for screening identified (eg: women between 25-55)
Cost effective
Natural history of disease must be known
Early/ latent stage recognizable
Suitable test (safe, acceptable to public, appropriate for condition).
Effective+ acceptable treatment
Continuous process (not a one off event)
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10. True positives/ negatives
True positive: result is positive and they actually have the disease.
True negative: result is negative and they actually don’t have the disease.
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11. False positives/ negatives
False positive: result is positive but they actually don’t have the disease.
False negative: result is negative but they do have the disease.
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12. Sensitivity, specificity, PPV and NPV definitions:
Sensitivity: ability of a test to correctly identify those with the disease.
Specificity: ability of test to correctly exclude those who don’t have the disease.
PPV: proportion of the positive results that are true positives.
NPV: proportion of the negative results that are true negatives.
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13. The table
In terms of the letters a, b, c, d write down the calculations for sensitivity, specificity, PPV and NPV:
Sensitivity= a/ (a+c)
Specificity= d/ (b+d)
PPV= a/ (a+ b)
NPV= d/ (c+d)
Sensitivity a/ (a+c)
Specificity d / (b+d)
PPV: a / (a+ b)
NPV: d/ (c+d)
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14. Limitations of screening
False positives: unnecessary worry/ stress to those who don’t have the disease
Negative results: people feel they have a license to take risks.
Over detection of sub-clinical (“harmless”) cases
“Harm” from screening: (eg: radiation exposure from mammography).
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15. Limitations of screening
What are the limitations of using PSA as a screening test for prostate cancer?
What is the limitation of using a D-dimer to detect PE? Is it a sensitive/ specific test?
Limitations of PSA: it is not very specific to prostate ca as it can be elevated by a number of conditions (eg: prostatis).
D-dimer is very sensitive (picks up a PE if it’s there) but not very specific (can be elevated due to a number of conditions incl. pregnancy).
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16. Risk
Absolute risk: risk of developing a disease (eg: lung cancer) over a time period. Eg: risk of lung cancer is 45/ 300 in smokers and 5/700 in non smokers.
Relative risk: risk of getting a disease (eg: lung cancer) in exposed group (eg: smokers) compared to an unexposed group (eg: non-smokers). It’s a ratio so has NO UNITS. Eg: 45/300 divided by 5/700 = 21.4 x the risk of lung cancer in smokers compared to non smokers.
Attributable risk (AR) aka ARR (absolute risk reduction): rate of disease in exposed that may be attributed to exposure. Ie: incidence in exposed minus incidence in unexposed. Eg: 45/300 – 5/700.
Patient UK have a good page on this
Attributable risk and ARR will give the same number but one is positive and one is negative.
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17. ARR and NNT
NNT: how many people need to be treated for one person to benefit? How do you calculate NNT? NNT= 1/ ARR Remember if you get an NNT of 6.99 round it up because you can’t have 6.99 of a person!
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18. Never events
Definition: a serious, largely avoidable patient safety event which should not occur if the available preventative measures have been implemented.
Never event definition?
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19. Never event examples… Wrong site surgery/ foreign object retained.
Wrong drug dose/ route.
ABO incompatibility.
Mental health: escape of transfer patient.
Never event definition?
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20. Human error Error: an unintended outcome.
Neglect: falling below the acceptable standard of care.
Types of error:
Errors of commission: doing something.
Errors of omission: not doing something.
Examples:
Sloth error: being lazy, not checking.
Communication break down.
Lack of skill.
Lack of knowledge.
Difference between error and neglect
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21. Swiss Cheese model
Each layer represents processes which have been put in place to prevent errors happening.
Holes are where processes can fail.
When the holes in the cheese line up an error can occur.
Latent errors: first 3 layers.
Active error: unsafe act.
Latent errors: errors in the system (Eg: not having two people to check a drug chart)
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22. Negligence
Breach of legal duty of care owed which results in harm to that patient.
Was there a duty of care?
Was that duty of care breached?
Did the patient come to harm?
Was the harm due to the breach in duty of care?
Negligence definition?
4 questions?
2 tests?
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23. 2 tests of negligence?
Bolam: would a group of reasonable doctors have done the same?
Bolitho: would it have been reasonable of them to do so?
Negligence definition?
4 questions?
2 tests?
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24. Patient Compliance Factors affecting patient compliance:
Socioeconomic – related factors eg. long distance from treatment setting
Health system – related factors eg. supply of medication
Condition – related factors eg. memory impairment
Therapy – related factors eg. complex treatment regimens
Patient – related factors eg. disbelief/denial of diagnosis
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25. Coronary Artery Disease –
Risk Factors
Traditional Risk Factors
Other Risk Factors
Increased Age
Sedentary Lifestyle
Male Gender
Psychosocial Wellbeing
Family History
Alcohol Consumption
Smoking
Genetic Factors
Obesity
Plasma Lipoprotein(a) concentration
Hypertension
Coagulation Factors
Hyperlipidaemia
C-Reactive Protein
Diabetes Mellitus
NSAIDs
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26. Substance Misuse Interventions
Principles of treatment:
Minimise harm eg. decrease risk of blood-borne virus infection/transmission
Substitute prescribing eg. methadone or buprenorphine for opioid addiction
Psychosocial interventions
Residential treatment
Self-help groups
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27. Meningitis and Immunization
Meningitis usually refers to a serious infection of the meninges and bacterial meningitis is fatal unless treated.
Meningitis B vaccine – 3 doses given at 8weeks, 16weeks and 1year of age
5in1 vaccine - 8, 12 and 16 weeks of age
Pneumococcal vaccine - 3 doses given at 8weeks, 16weeks and 1year of age
Hib/Men C vaccine – one dose at 1year of age
Meningitis ACWY vaccine (protects against meningococcal groups A, C, W and Y) – one dose at 14years (as a replacement for 12week Men C vaccine)
Meningitis B vaccine (protection against meningococcal group B bacteria)
5in1 vaccine (protection against Hib bacteria)
Pneumococcal vaccine (protects against pneumococcal bacteria)
Hib/Men C (protects against Hib and Meningococcal group C bacteria)
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28. Pandemic Influenza
Endemic – disease permanently present within a population in a particular geographical area and /or normal prevalence of the disease
Epidemic - an increase in the prevalence of a disease above the number usually observed in the population in a particular area
Pandemic – an epidemic which occurs in several countries or continents
3 Influenza pandemics occurred in the 20th centaury. During a pandemic, most people will have limited immunity to the virus due to the absence of previous exposure.
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29. Confidentiality What are the 3 times you can break confidentiality?
If they are a risk to the public (they intend to commit a crime). Ie: benefits to society/ an individual outweigh the benefits of maintaining confidentiality.
If they have given consent.
If it is required by law: notifiable diseases (eg: ebola), a judge orders you to do so (eg: as part of a GMC investigation).
In these scenarios you must always try to get their consent but you don’t need it.
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30. Please refer to the Phase 2a curriculum for the topics we were unable to cover during this teaching session.
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