神經內科 王志弘
+ 治療或處置的危害
+ 環境的危害
+ Systemic review of randomized trials
– 單獨一個研究，常常無法顯示出一些少見的不
良反應
+ Cohort study
+ Case control studies
+ Cross-sectional studies
Included Subjects
Randomised to aspirin or placebo
aspirin
placebo
Myocardial infarction yes
no
5 years
Randomized Controlled Trial
Longitudinal study
4
Included Subjects
smoking status measured
smokers
Lung cancer
non-smokers
yes
no
+ Cohort study
+ Longitudinal study
5 years
5
Included Subjects
smoking status measured
smokers
Lung cancer
non-smokers
yes
no
+ Case Control Study
+ Longitudinal study
10 years
6
Included Subjects
smoking status measured
smokers
Lung function
non-smokers
normal
abnormal
+ Cross-sectional study
7
Are the results of this harm/etiology study valid?
+ 控制組
+ 客觀、或盲化（blind）
– 治療、暴露、結果
+ 追蹤：
– 時間：是否夠長
– 完整性：lost to follow up （<20%）
+ 因果相關
Case Control
RCT or cohort
+ Confounding factor: exposed and non-
exposed not randomized
+ Prospective vs retrospective
Retrospective cohort
 Administrative databases
 健保資料庫

+ the outcome of interest is rare or takes a long
time to develop
– 腫瘤、矽肺病
– 只能使用 case control study
+ 有些 confounder 無法測量
– Transient
– To severe leading to death
+ The selection of control
+ Statistical significance, if large number of
association factors
+ Exposure and outcome are measured at the
same time
+ case reports of one patient (or a case series of
a few patients)
– Thalidomide and 海豹肢症
+ highlight the need for other studies
+ Blind, objective
+ Administrative database
– 健保資料庫，病歷紀錄
+ Patient or doctor recall
+ 統計相關不等於因果相關
+ Diagnostic tests for causation
– the exposure preceded the onset of the outcome
– a dose–response gradient?
– dechallenge–rechallenge
– the association consistent from study to study
+ Does the association make biological sense?
Are the valid results of this harm study important?
Magnitude, precision
Case Control
RCT or cohort
RCT or cohort
+
20
980
2
998
Case Control
+
90
45
10
55
+ risks = odds/(1 + odds)
+ odds = (risk/1 – risk)
+ ORs and RRs >1：接觸者得病的機會增加
+ ORs and RRs <1：接觸者得病的機會減少
+ 通常
– case control study, OR >4, 認為有意義
– Cohort study, RR>3 就認為有意義
– 還要考慮結果（outcome）的嚴重程度
+
http://ktclearinghouse.ca/cebm/toolbox/ortonnt
+ Confidence Interval
+ the adjusted OR for ischemic heart disease or
stroke associated with a 25% lower serum
homocysteine level was 0.89 with 95% CI
0.83–0.96.
+ In our caffeine study, the OR was 2.4 (adjusted
for age and smoking) with 95% CI 1.1–6.5.
Can this valid and important evidence about harm be applied to our
patient?
研究方法?
RCT, cohort, case control, cross-sectional