Measures of Association

Max SanamFKH UndanaMeasures of AssociationRisikoRisiko adalah probabilitas terjadinya suatu peristiwaSuatu keadaan atau faktor yang menentukan terjadi atau tidak terjadinya suatu hal dinamakan faktor risikoPecah ban merupakan faktor risiko bagi kejadian kecelakaan kendaraan bermotorHipertensi adalah faktor risiko bagi penyakit jantung koroner.Vaksinasi adalah suatu faktor risiko protektif yang biasanya menurunkan risiko penyakitJika 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.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 tertentu untuk melihat kejadian penyakit Jika kedua variabel paparan (exposure) dan outcome bersifat biner (ya atau tidak), hasilnya dapat disajikan dalam suatu tabel 2 2.

Berbagai ukuran asosiasi dapat dikalkulasi: (1) measures of strength, (2) measures of effect, and (3) measures of total effect.

DiseasedNon-diseasedTotalExposedaba+ bNon-exposedcdc+ d Totala + cb+ da+b+c+d = nIncidence 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/bOdds of disease in the non-exposed population: OO = c/dDiseasedNon-diseasedTotalExposedaba+ bNon-exposedcdc+ d Totala + cb+ da+b+c+d = nUkuran-Ukuran KekuatanRisk ratio (RR)RR didefinisikan sebagai rasio risiko penyakit (i.e. the incidence risk) di dalam kelompok terpapar terhadap risiko penyakit di dalam kelompok tidak terpaparRR = RE / RO

RR memberikan estimasi berapa banyak kali kemungkinan bagi individu yang terpapar untuk mengalami penyakit dibandingkan individu yang tidak terpapar faktor risikoJika risk ratio = 1, maka risiko sakit di dalam kelompok terpapar dan tidak terpapar adalah samaRisk Ratio ...Jika RR > 1, maka exposure meningkatkan ririko kejadian penyakitJika RR < 1, exposure menurunkan risiko kejadian penyakit dan disimpulkan sebagai protektif. Risk ratio cannot be estimated in case-control studies, as these studies do not allow calculation of risks. Pada CC study, Odds ratios (OR) yang digunakan dan bukan RRNilai RR berkisar antara 0 dan tak terhingga.Odds ratioThe odds ratio is the odds of disease, given exposure. The odds ratio (OR) is an estimate of risk ratio and is interpreted in the same way. OR is calculated as:OR = OE / OO = ad / bcWhen the number of cases of disease is low relative to the number of non-cases (i.e. The disease is rare), then the odds ratio approximates risk ratio.Ukuran-ukuran Dampak di dalam Populasi terpaparAttributable risk (rate)Attributable risk (or rate) is defined as the increase or decrease in the risk (or rate) of disease in the exposed group that is attributable to exposure. AR (unlike RR) describes the absolute quantity of the outcome measure that is associated with the exposureAR is calculated as: AR = RE ROAttributable 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) / RRFor case-control studies, AF can be approximated:AFest = (OE OO) / OE = (OR 1) / ORSuatu studi Kasus-Kontrol : efek vaksinasi oral terhdap ada atau tidaknya rabies pada srigala.

odds rabies kelompok tidak divaksinasi adalah 2.3 odds rabies kelompok vaksinasi (OR = 2.30).Lima puluh enam % kasus rabies pada srigala yang tidak divaksinasi adalah karena tidak divaksinasi (AF est = 0.56).Rabies +Rabies -TotalVaccination -183048Vaccination +124658Total3076106Ukuran-Ukuran Efek pada PopulasiPopulation attributable risk (rate)PAR is the increase or decrease in risk (or rate) of disease in the population that is attributable to exposure. PAR is calculated as: PAR = RTotal ROPopulation attributable fraction (also known as the aetiologic fraction) is the proportion of disease in the population that is due to the exposure. PAF = (R Total RO) / R Total

Suatu studi Potong-Lintang diterapkan menyelidiki hubungan antara dry cat food (DCF) and feline urologic syndrome (FUS)Hasil penelitian sbb:FUS +FUS -TotalDCF +1321632176DCF -533493354Total3055125530The incidence risk of FUS in the DCF+ group was 5.97 cases per 1000. The incidence risk of FUS in the DCF- group was 1.49 cases per 1000. The incidence risk of FUS in DCF 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).FUS +FUS -TotalDCF +1321632176DCF -533493354Total3055125530The incidence risk of FUS in the cat population that may be attributed to DCF is 1.8 per 1000.That is, we would expect the risk of FUS to decrease by 1.8 cases per 1000 if DCF were not fed (PAR = 0.0018). Fifty-four percent of FUS cases in the cat population are attributable to DCF (PAF = 0.54).FUS +FUS -TotalDCF +1321632176DCF -533493354Total3055125530Penggunaan ukuran-ukuran dampak secara tepatParameterCase-ControlCohortCross-sectionalMeasures of strength:RRNoYesYes (Prevalence RR)ORYesYesYes (Prevalence OR)Measures of effect:ARNoYesYesAFNoYesYesAFestYesYesYesMeasures of effect in population (total effect):PARNoYesYesPAFNoYesYesPAFestYesYesYes