6. Studi Deskriptif & Kasus Kontrol (Mhs) b

4/21/2010Case-Control Study (MHS)CASE-CONTROL STUDYMochammad Harris SuhamihardjaLECTURE 6B*

Case-Control Study (MHS)

4/21/2010Case-Control Study (MHS) LECTURE 6B CASE-CONTROL STUDY *


4/21/2010Case-Control Study (MHS)b. ANALYTIC STUDIES (Comparative)

By comparing 2 groups or more:- determine causality (etiology) of a problem 3 type of analytical studies:1. Cross-sectional Studies2. Case-Control Studies3. Cohort Studies*


4/21/2010Case-Control Study (MHS) 2. Case- control StudiesFocus : comparing describing

*


4/21/2010Case-Control Study (MHS)In the early 1940, Alton Ochsner, a surgeon in New Orleans observed that all patients of pulmonary cancers he operated, have history of cigarette smoking. At this time, such association can be accepted and recognized. At that time is a new one and controversial.Ochsner made a hypothesis that smoking is related to pulmonary cancer based only on observation.

Is this conclusion correct? EXAMPLE 1*


4/21/2010Case-Control Study (MHS)

Other event in 1940s, Sir Norman Gregg, an Australian ophthalmologist observed in his practice, a number of infants and small children had cataracts.

Gregg observed that while the kids were in uterus,there were German measles outbreak. Gregg thought that there were an association between rubella prenatal mothers with cataracts.Remember, at that time there is no knowledge about teratogenic virus.

EXAMPLE 2*


4/21/2010Case-Control Study (MHS)2. Case-Control StudiesPast NoRisk Factor (+)CaseCompareRisk Factor (+)Risk Factor (-)ControlRetrospectiveRisk Factor(-)*


4/21/2010Case-Control Study (MHS)2. Case-Control StudiesPastNowretrospective

Control Confounding Variablesmatching

*


4/21/2010Case-Control Study (MHS)Disease(+)Disease(-)Exposed(+)Exposed(-)A case-control designExposed(+)Exposed(-)*


4/21/2010Case-Control Study (MHS)CASE Disease+

aa + cCONTROLDisease-

bb + dExposure (+) a b Non-exposure(-) c dTOTAL a + c b + dExposed proportion

First time, chooseThen,Measures exposure in the past.*


4/21/2010Case-Control Study (MHS)TABEL 2 X 2*

DISEASE(+)DISEASE(-)TOTALEXPOSURE(+)aba + bEXPOSURE(-)cdc + dTOTALa + cb + da + b + c + d


4/21/2010Case-Control Study (MHS) Table 9-2 Hypothetical Example of a Case-Control Study of CHD and Cigarette smoking*

EXPOSURECHDControl

Smoking 112176Non-smoking88224Total200400% Smoking56.044.0


4/21/2010Case-Control Study (MHS)Leon Gordis, p.126Table 8.3 History of Use of Artificial Sweeteners in Bladder Cancer Cases and Controls*

Use of Artificial sweetenersCASECONTROL

Use1,2932,455No use1,7073,321Total3,0007,776


4/21/2010Case-Control Study (MHS)From Doll R, Hill ABLeon Gordis, p.126Table 9.4 Distribution of 1,357 Male Lung Cancer Patients and a Male Control Group According to Average Number of Cigarettes Smoked Daily Over the 10 Years Preceding Onset of the Present Illness*

Average cigarette dailyCASECONTROL

01-45-1415-2425-49 50+Total755489475293381,35761 129570431154121,357


4/21/2010Case-Control Study (MHS)CASE AND CONTROL SELECTIONCASE SELECTIONSources:- Hospital patients- Patients of Private Practice- Clinical patients- Patient registration in the community.*


4/21/2010Case-Control Study (MHS)CASE SELECTIONProblem :- If cases selected only from one hospital?- If the hospital is the third reference hospital?

Selection criteria should be written specifically and accurately. - Cases: incidence or prevalence ?*


4/21/2010Case-Control Study (MHS)CONTROL SELECTION

SOURCE

- Outpatients and live in a community.-neighbors-friends-couples- In- patients of a hospital*


4/21/2010Case-Control Study (MHS)CONROL SELECTIONSOURCE :- Hospital patients- Advantages:* Captive population* Cost is relatively not expensivea- DisadvantagesSample is not a representative of a population in the community.

From the similar hospital ? All other in-patients?*


4/21/2010Case-Control Study (MHS)Keuntungan menggunakan population-based dan hospital-based case-control studyGreenberg, p. 132*

Population-basedCCSHospital-basedCCSPopulasi dapat ditetapkan secaralebih baik

Lebih mudah memastikan bahwa kasus dan kontrol berasal dari populasi yang sama.

Riwayat keterpaparan dari kontrol lebih mencerminkan orang-orang tanpa penyakit yang diselidiki Subyek lebih mudah dijangkau

Subyek cenderung lebih kooperatif

Latarbelakang karakteristik kasus dan kontrol dapat diseimbangkan Lebih mudah mengumpulkan informasi keterpaparan dari rekam medis dan spesimen biologis


4/21/2010Case-Control Study (MHS)DISEASE -DISEASE +PopulationCASESampleSamplingCONTROLSamplingExposedNon-exposed THE ORIGIN OF SELECTION BIASGreenberg, p.132*


4/21/2010Case-Control Study (MHS)MATCHINGIs a process of control selection by using some characteristics similar to the cases, e.g.age, sex, race, gender, occupation and social economic status.(1) GROUP MATCHING(2) INDIVIDUAL MACHINGMATCHING *


4/21/2010Case-Control Study (MHS)MATCHING GROUP MATCHING (FREQUENCY MATCHING)Proportion of a certain characteristics of control are similar with case group.e.g :

If 25 % of a case group 25 % of the control group married marriedALL CASES SELECTED FIRST !!!!*


4/21/2010Case-Control Study (MHS)MATCHING INDIVIDUAL MATCHING (MATCHED PAIRS)

For each case selected, the control has a similar variable.

Use control from the hospital.*


4/21/2010Case-Control Study (MHS) INDIVIDUAL MATCHING (MATCHED PAIRS)

PROBLEMS WITH MATCHING ?PRACTICAL PROBLEMTO MUCH CHARACTERISTICS TO BE MATCHED? DIFFICULT OR IMPOSSIBLE TO FIND APPROPRIATE CONTROL

2) CONSEPTUAL PROBLEMAFTER MATCHING WITH CERTAIN CHARACTERISTICS, WE CANNOT STUDY FURTHER THOSE CHARACTERITICS.*


4/21/2010Case-Control Study (MHS)PROBLEMS OF RECALL2 TYPE :(1) Limitation of recalls(2) Recall bias*


4/21/2010Case-Control Study (MHS)PROBLEMS OF RECALL Limitations of recall

- Data collection from subjects by interviewing.

- Human has limitation of information recall*


4/21/2010Case-Control Study (MHS)PROBLEMS OF RECALL Recall bias

A serious problem in case-control studies*


4/21/2010Case-Control Study (MHS)USE OF MULTIPLE CONTROLS SIMILAR TYPE CONTROL UNSIMILAR TYPE CONTROL*


4/21/2010Case-Control Study (MHS) CONTROL WITH SIMILAR TYPE

FOR EACH CASE USES 2 OR 3 CONTROLS THE OBJECTIVE IS TO INCREASE THE POWER OF THE STUDYTHE RATIO CAN BE 1 CASE FOR 4 CONTROLSWhy not to limit the ratio 1: 1 by adding the number of cases?

FOR THE MOST RARE CASES, THE NUMBER OF THE AVAILABALE CASES IS LIMITED.USE OF MULTIPLE CONTROLS*


4/21/2010Case-Control Study (MHS)CONTROL WITH DIFFERENT TYPESe.g.

Cerebral tumor CASEOther Cancer CONTROLNormalCONTROLPrenatalHistory of radiation exposed WITHOUTHISTORYCHILDRENUSE OF MULTIPLE CONTROLS*


4/21/2010Case-Control Study (MHS)FINISHThank You*


4/21/2010Case-Control Study (MHS)*


6. Studi Deskriptif & Kasus Kontrol (Mhs) b

Documents

Transcript of 6. Studi Deskriptif & Kasus Kontrol (Mhs) b