EPIDEMIOLOGY. Joedo Prihartono

Transcription

1 EPIDEMIOLOGY Joedo Prihartono 1

2 EPIDEMIOLOGY As a supporting science Focusing on the following aspects: Disease frequency Distribution of disease Determinant factor 2

3 EPIDEMIOLOGICAL QUESTIONS WHAT Disease frequency WHO Personal distribution WHERE Geographical distribution WHEN Time distribution WHY Determinant factors HOW Pathogenesis 3

4 MEASUREMENT Absolute measurement Can mislead Relative measurement More objective 4

5 INCIDENCE RATE Σ New cases in one period Σ Population at risk Based on period of time Population at risk as denominator Representing risk measurement To evaluate preventive program 5

6 NEW CASE ADMISSION The time to admit as a new case Chronic disease more difficult Could jeopardize statistics The time when confirmed diagnostics 6

7 PREVALENCE RATE Σ New & Old cases at time Σ All population member Representing a proportion At a specific time To evaluate curative program 7

8 PERIOD PREVALENCE Σ Old cases at start + New cases Σ All population member Especially for psychiatric cases Difficult to determine condition Combined prevalence & incidence 8

9 INSIDENCE & PREVALENCE Jan Feb Mar Apr Mei Jun Jul Agu Sep Okt Nop Des

10 RELATIONSHIP P = I x d Incidence Prevalence 10

11 RATIO & PROPORTION RATIO Independent comparison No relationship between nominator and denominator PROPORTION A/B Nominator is part of the denominator A/(A+B) 11

12 GENERALIZATION Using interval estimation Based on inference theory Using 95% Confidence Interval π = P +/- Zα PQ/n 12

13 DISEASE CLASSIFICATION International comparison WHO International Standard ICD = International Classification of Diseases Etiological criteria Manifestation criteria 13

14 CRITERIA RELATION Etiological Criteria Manifestation criteria POSITIVE NEGATIVE POSITIVE Classic case Sub clinical Carrier NEGATIVE Recovery Psychosomatics Healthy 14

15 DISEASE DISTRIBUTION Not a random process Affected by determinant factors Intrinsic factors = Genetics Extrinsic factors = Exposure WHO WHERE WHEN 15

16 PERSONAL FACTORS Sex Age Socio economics Education Religion Ethnic Etc 16

17 SEX RELATED DISTRIBUTION MALE FEMALE o Hemophilia o Hypertension o Stress o Traffic accident o Diabetes mellitus o Anemia o Iodine deficiency o Household accident 17

18 GEOGRAPHIC DISTRIBUTION URBAN RURAL o Obesity o Depression o Pollution o Traffic accident o Leptospirosis o Brucellosis o Pollen allergic o Other zoonosis 18

19 SEASONAL DISTRIBUTION DRY MOONSOON RAINY MOONSOON o Cough o Pharyngitis o Dengue o Malaria o Diarrhea o Influenza o Typhoid fever o Dysentery 19

20 EPIDEMIOLOGICAL TRANSTITION Acute Chronic

21 CAUSAL RELATIONSHIP Must be happened many times Temporal relationship Dose relationship A A+p A-x B B+q B-y 21

22 SYSTEMATIC STEPS A B Significant Not significant Causal Coincidence Direct Indirect 22

23 EPIDEMIOLOGY CYCLE Review of facts and theories Inductive Deductive Testing Generate hypothesis hypothesis 23

24 CAUSAL HYPOTHESIS Representing temporary answer Description of affected population Description of specific cause Description of specific effect Dose response relationship Temporal relationship 24

25 GENERATING HYPOTHESIS Method of agreement Method of difference Method of concomitant variation Method of analogy 25

26 RISK MEASUREMENT Determinan Case Cont Tot Positive a b a+b Negative c d c+d Total a+c b+d n 26

27 PROSPECTIVE STUDY Exposed Incidence rate Non exposed Incidence rate Relative Risk (RR) RR= Exposed Incidence rate Non exposed Incidence rate RR (1+1,96/Chi) 27

28 RETROSPECTIVE STUDY Unable to measure Incidence rate Unable to calculate Relative Risk Estimate using Odds Ratio (OR) OR = a x d b x c OR (1+1,96/Chi) 28

29 ETIOLOGICAL FACTOR (O)RR > 3 Clear etiology 3 > (O)RR > 2 Questionable 2 > (O)RR > 1 Not an etiology 29

30 PREVENTIVE FACTOR (O)RR < 0,3 Clear preventive 0,3 < (O)RR < 0,5 Questionable 0,5 < (O)RR < 1,0 Not preventive 30

31 COMMUNICABLE DISEASE Pathogenic biological agent Mode of transmission Vulnerable host Port of entry Port of exit Reservoir (environment, etc) 31

32 CHAIN OF TRANSMISSION Agent Vehicle Host Patient Patient Host Vehicle Agent 32

33 PREVENTION Break the chain of transmission Host Agent Environment 33

34 PREVENTION PROGRAM Agent Host Ports Transmission Reservoir Case finding/therapy Immunisation Education behavior Sanitation 34

35 LEVELS OF PREVENTION Health promotion Specific protection Early diagnostics and prompt treatment Disability limitation Rehabilitation 35

36 36