前瞻性研究
前瞻性的研究(prospective study)是以现在为起点追踪到将来的研究方法，可弥补回顾性研究的缺陷。例如临床心理学实验中，对一批A型行为类型者使用自我行为管理策略指导，并追踪此后整个行为干预策略实施过程中被A型行为的改变情况，从而证明这种治疗技术的实际效果。（百度）
A prospective study watches for outcomes, such as the development of a disease, during the study period and relates this to other factors such as suspected risk or protection factor(s). The study usually involves taking a cohort of subjects and watching them over a long period. The outcome of interest should be common; otherwise, the number of outcomes observed will be too small to be statistically meaningful (indistinguishable from those that may have arisen by chance). All efforts should be made to avoid sources of bias such as the loss of individuals to follow up during the study. Prospective studies usually have fewer potential sources of bias and confounding than retrospective studies.
回顾性研究
回顾性研究就是以现在为结果，回溯过去的研究方法。例如对已经患有肺癌的患者和正常人群进行分析，比较他们之前生活方式有什么不同，从而找出可能导致肺癌的危险因素。这一研究方式由于条件限制较少，有其优点，但其缺陷是被试目前的身心状态会影响对过去资料报告的真实性和准确性。
A retrospective study looks backwards and examines exposures to suspected risk or protection factors in relation to an outcome that is established at the start of the study. Many valuable case-control studies, such as Lane and Claypon's 1926 investigation of risk factors for breast cancer, were retrospective investigations. Most sources of error due to confounding and bias are more common in retrospective studies than in prospective studies. For this reason, retrospective investigations are often criticised. If the outcome of interest is uncommon, however, the size of prospective investigation required to estimate relative risk is often too large to be feasible. In retrospective studies the odds ratio provides an estimate of relative risk. You should take special care to avoid sources of bias and confounding in retrospective studies.
病例对照研究
Case-Control studies
outcome is measured before exposure
controls are selected on the basis of not having the outcome
good for rare outcomes
relatively inexpensive
smaller numbers required
quicker to complete
prone to selection bias
prone to recall/retrospective bias
related methods are risk (retrospective), chi-square 2 by 2 test, Fisher's exact test, exact confidence interval for odds ratio, odds ratio meta-analysis and conditional logistic regression.
队列研究
Cohort studies
Cohort studies are usually but not exclusively prospective, the opposite is true for case-control studies. The following notes relate cohort to case-control studies:
outcome is measured after exposure
yields true incidence rates and relative risks
may uncover unanticipated associations with outcome
best for common outcomes
expensive
requires large numbers
takes a long time to complete
prone to attrition bias (compensate by using person-time methods)
prone to the bias of change in methods over time
related methods are risk (prospective), relative risk meta-analysis, risk difference meta-analysis and proportions
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