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RME L2 Determine causation (Issues to consider (Etiology of chronic ds…

- - - - We infer causation based on Association & several other factors
  - - - Suggestions for Assessing causality
      - :nine: ข้อ
        
        Strength of association
        
        Strong associations r more likely to be casual than weaker associations
        
        The larger the RR or OR, the greater the likelihood that relationship is casual
        
        Strong asso = High chance that those 2 are considerable causes of each other
        
        :warning: ข้อโต้แย้ง Low assoc may be cause of ds
        
        Measures of associations — quantify strength of association between Exposure & Outcome
        eg. Relative risk (RR), Odds ratio (OR)
        
        Consistency/ความมั่นคง
        
        :warning: ขตย.: ขาด consistency -> still can’t say that its not cause of ds
        (as it can caused fr many factors)
        
        Specificity
        
        Touch with สิ่งคุกคามชนิดนี้ จะป่วยเป็นโรคนี้เสมอ. (one-to-one relationship)
        
        :warning:ขตย.: ไม่เหมาะมาใช้กะปจบ.
        As we believe that Ds caused by many causes (1 cause may cause many ds)
        
        Temporality
        
        Necessity for the exposure to precede the outcome (effect) in time
        
        = consider Time sequence association (การเรียงลำดับเวลาของค.สัมพันธ์) —เหตุต้องมาก่อนผลเสมอ ไม่ว่าโรคนั้นจะมีระยะเวลาก่อโรคสั้นหรือยาวนานเท่าใด
        
        Biological gradient
        
        Dose-Response relationship (Biological gradient)
        :relationship between Dose (amount of exposure) to a substance and results in changes in outcome (response)
        
        :arrow_up:level of exposures -> :arrow_up:risk of outcome
        
        Plausibility
        
        Biological plausibility of hypothesized causal relationship between Exposure and outcome
        
        พิจารณาความเป็นไปได้ทาง biology ว่าความรู้ในปจบ. Can explain mechanism of ds fr expose to threatened stuffs
        
        Examples
        
        Eg. Will smoking resulting in receiving some sort of carcinogen eg Benzo(a)pyrene via smoke then cause reaction with lung tissues so :arrow_up:chance of getting CA Lung
        
        A high dose of caffeine could constrict a mother’s blood vss reducing the blood flow to the placenta
        
        Coherence
        
        พิจารณาความสอดคล้องของความสัมพันธ์
        มุ่งให้พิจารณา ลักษณะของ relationที่พบ not conflict with Basic knowledge abt ds or nature of ds
        
        Eg. smoking & CA Lung isn’t conflict with nature of founded disease
        (as men smokes > female so CA Lung found more in men > female)
        
        Experiment evidence
        
        Are there any clinical studies supporting the association?
        
        Some case try :arrow_down:exposure to threatened stuff & look for changes in disease rate
        
        Eg. try advice abt :arrow_down:smoking in population then found that :arrow_down:CA lung rate
        = support smoking causes CA lung
        
        Analogy
        
        พิจารณาการเปรียบเทียบอุปมา
        
        Eg.eat Thalidomide may cause Fetal in womb abnormality
        -> consider drugs’ effect to fetus — believe that other drugs can also be the cause of abnormality of fetus
        
        Analogy = ดูแล้วมันคล้ายๆกับ factor อื่นๆ
        Eg smoking cigarette cause CA Lung, so smokes ใบจาก cause CA Lung
      - Criteria ของการพิจารณาว่าอะไรนั้นเป็นเหตุเป็นผลกัน
- - - - :stars: First ds to be discovered = Anthrax
      - Finding which organisms causes ds??
        Koch’s postulate (1980)
        
        Casual relationship between a Microbe & a Disease
        
        Isolate & culture ได้
        
        เอาเชื้อที่isolate then inject into animals then the said animals got ds
        
        ตรวจพบเชื้อในสัตว์
        
        พบเชื้อในทุกคนที่เกิดโรค
        
        Limitations
        
        Some organisms can’t be grown in pure culture
        
        Uses humans in completing the postulate is Unethical
        
        Molecular & genetic evidence may replace
    - - High infectious ds
      - Infectious only with Symptoms
    - - Infectious ds without symptoms
      - Ds that has multiple causes
  - - - Ds causes fr Imbalance of one of the three (host, agent, environmental)
    - - Applied to
        Phenylketonuria(PKU) — archetypal genetic ds
        
        Autosomal single gene ds
        
        Lacks an enzyme that required to metabolise the dietary amino a Phenylalanine & turn it into Tyrosine
      - Emphasizes Unity of gene & host within an interactive environmental envelope
        (3 ปัจจัยสวล— Physical env, Social env, Chemical&Biological environment)
    - - For many disorders - we understand that causes are highly complex
      - Multifactorial / Polyfactorial disorders
      - Mechanism of causation r not apparent
      - Points that a Potential for ds to influence the causes & not just the other way around — reverse causality
      - In the middle is ds -> outward is direct causes -> outest circle is Environment that causes ds
    - - Casual & Mechanisms understood (เข้มแข็งสุด —ปลายแหลมpyramid)
      - Casual (free independent
        eg. Eat salty can causes HT
      - Non-casual (no relation between 2 ตัว แต่รู้ว่ามันส่งเสริมคู่กัน) eg สุรา&เหล้า
      - Confounded
      - Spurious / Artefact
      - Chance