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Measures of Association

Measures of Association. Max Sanam FKH Undana. Risiko. Ris iko adalah probabilitas terjadinya suatu peristiwa Suatu keadaan atau faktor yang menentukan terjadi atau tidak terjadinya suatu hal dinamakan faktor risiko

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Measures of Association

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  1. Measures of Association Max Sanam FKH Undana

  2. Risiko • Risiko adalah probabilitas terjadinya suatu peristiwa • Suatu keadaan atau faktor yang menentukan terjadi atau tidak terjadinya suatu hal dinamakan faktor risiko • Pecah ban merupakan faktor risiko bagi kejadian kecelakaan kendaraan bermotor • Hipertensiadalah faktor risiko bagi penyakit jantung koroner. • Vaksinasi adalah suatu faktor risiko protektif yang biasanya menurunkan risiko penyakit

  3. Jika kita mengidentifikasi berbagai faktor risiko yang memiliki hubungan kausatif dengan kemungkinan meningkat atau menurunnya suatu penyakit • Hasilkan rekomendasi bagi pengelolaan kesehatan. • Riset epidemiologis estimasi dan kuantifikasi faktor-faktor risiko dari penyakit.

  4. Asoasiasi antara faktor risiko (paparan) dan outcome (biasanya penyakit) dapat diselidiki menggunakan studi-studi observasional • Bayangkan suatu studi dimana pada awalnya subjek bebas penyakit dan kemudian dimonitor selama periode waktu tertentuuntuk melihat kejadian penyakit

  5. Jika kedua variabel paparan (exposure)dan outcome bersifat biner (yaatautidak), hasilnya dapat disajikan dalam suatu tabel 2 × 2. • Berbagai ukuran asosiasi dapat dikalkulasi: (1) measures of strength, (2) measuresof effect, and (3) measures of total effect.

  6. Incidence risk in the exposed population: RE = a/(a + b) • Incidence risk in the non-exposed population: RO = c/(c + d) • Incidence risk in the total population: RTotal = (a + c)/(a + b + c + d) • Odds of disease in the exposed population: OE = a/b • Odds of disease in the non-exposed population: OO = c/d

  7. Ukuran-Ukuran Kekuatan Risk ratio (RR) • RRdidefinisikan sebagai rasio risiko penyakit (i.e. the incidence risk) di dalam kelompok terpapar terhadap risiko penyakit di dalam kelompok tidak terpapar RR =RE / RO • RR memberikan estimasi berapa banyak kali kemungkinan bagi individu yang terpapar untuk mengalami penyakit dibandingkan individu yang tidak terpapar faktor risiko • Jika risk ratio=1, maka risiko sakit di dalam kelompok terpapar dan tidak terpapar adalah sama

  8. Risk Ratio ... • Jika RR > 1, maka exposure meningkatkan ririko kejadian penyakit • Jika RR < 1, exposure menurunkan risiko kejadian penyakit dan disimpulkan sebagai protektif. • Risk ratio cannot be estimatedin case-control studies, as these studies do not allow calculation of risks. • Pada CC study, Odds ratios (OR) yang digunakan dan bukan RR • Nilai RRberkisar antara0 dan tak terhingga.

  9. Odds ratio • The odds ratio is the odds of disease, given exposure. • The odds ratio (OR) is an estimateof risk ratio and is interpreted in the same way. • ORis calculated as: OR =OE / OO=ad / bc • When the number of cases of disease is low relative to the number of non-cases (i.e. Thedisease is rare), then the odds ratio approximates risk ratio.

  10. Ukuran-ukuran Dampak di dalam Populasi terpapar Attributable risk (rate) • Attributable risk (or rate) is defined as the increase or decrease in the risk (or rate) ofdisease in the exposed group that is attributable to exposure. • AR(unlikeRR) describes the absolute quantity of the outcome measure that is associated withthe exposure • AR is calculated as:AR= RE − RO

  11. Attributable fraction (AF) • AF (attributable proportion in exposed subjects)is the proportion of disease in the exposed group that is due to exposure. • AF is calculated as: AF =(RE − RO) / RE=(RR − 1) / RR • For case-control studies, AF can be approximated: AFest =(OE − OO) / OE=(OR− 1) / OR

  12. Suatu studi Kasus-Kontrol : efek vaksinasi oral terhdap ada atau tidaknya rabies pada srigala. • odds rabies kelompok tidak divaksinasi adalah 2.3 odds rabieskelompok vaksinasi (OR = 2.30). • Lima puluh enam %kasus rabies pada srigala yang tidak divaksinasi adalah karena tidak divaksinasi (AFest= 0.56).

  13. Ukuran-Ukuran Efek pada Populasi Population attributable risk (rate) • PARis the increase or decrease in risk (or rate) ofdisease in the population that is attributable to exposure. • PARis calculated as: PAR= RTotal− RO

  14. Population attributable fraction (also known as the aetiologic fraction) is the proportionof disease in the population that is due to the exposure. PAF =(RTotal− RO) / RTotal

  15. Suatu studi Potong-Lintang diterapkan menyelidiki hubungan antara dry cat food (DCF) andfeline urologic syndrome (FUS) • Hasil penelitian sbb:

  16. The incidence risk of FUS in the DCF+ group was 5.97 cases per 1000. • The incidencerisk of FUS in the DCF- group was 1.49 cases per 1000. • The incidence risk of FUS inDCF exposed cats was 4.01 times greater than the incidence risk of FUS in DCF- cats(RR = 4.0). • The incidence risk of FUS in DCF+ cats that may be attributed to DCF is 4.5 per 1000(AR = 0.0045). • In DCF+ cats 75% of FUS is attributable to DCF (AF = 0.75).

  17. The incidence risk of FUS in the cat population that may be attributed to DCF is 1.8per 1000. • That is, we would expect the risk of FUS to decrease by 1.8 cases per 1000 ifDCF were not fed (PAR = 0.0018). • Fifty-four percent of FUS cases in the cat populationare attributable to DCF (PAF = 0.54).

  18. Penggunaan ukuran-ukuran dampak secara tepat

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