Advantages of hospital controls in case control studies

Advantages of hospital controls in case control studies

Therefore, hospital controls have been widely used in case-control studies. As hospital controls are not healthy individuals, the exposure distribution to risk factors under study may be unrepresentative of the base-population. She then consulted her personal physician, who performed a thorough evaluation. How should controls be selected? Hospital visitors as controls. References 1. In addition, random digit dialing doesn't make any distinction between residential and business phones. Epidemiology: principles and methods - Sources and methods for control selection. Friend controls are another way of selecting matched controls. Matching in a case—control study involves sampling of controls to parallel selected characteristics of cases in order to reduce the likelihood of confounding by the matched features.

Int J Epidemiol ; Cases and controls had to be residents of the metropolitan region of Rio de Janeiro Brazil for at least six months.

Matching in a case—control study involves sampling of controls to parallel selected characteristics of cases in order to reduce the likelihood of confounding by the matched features. Family history of breast cancer was a risk factor in Models 2 and 3, but no association was found in Model 1.

Regarding family history of cancer, there was seen great variation between the three models Table 4. Consequently, if it is time-consuming or expensive to collect data on controls, the ratio of controls to cases should be no more than These controls would have similar access to go to the deli if they chose to, and they would therefore be more representative of the source population.

The lack of other types of controls in this study limits the possibilities of better exploring the occurrence of selection bias.

case control study advantages

Oxford University Press Considering family history of breast cancer, selection bias due to the inclusion of 27 women visiting relatives with breast cancer masked the effect in Model 1. Women who had ever had breast cancer were ineligible.

The key to avoiding selection bias is to select the controls by a similar, if not identical, mechanism in order to ensure that the controls provide an accurate representation of the exposure status of the source population.

How to select controls in case control study

McCarthy and Giesecke. The study findings indicate that hospital visitor controls can create selection bias regarding family history of cancer. Eisemberg, MD and L. One advantage is that there is no need for a population register. By matching cases and controls on these factors, confounding by these factors will be controlled. Many but not all of the infected cases are identified by passive and active surveillance. Example 1: In the first example above, in which cases were randomly selected from a geographically defined database, the source population is also defined geographically, so it would make sense to select population controls by some random method. Epidemiology: an introduction. The observed odds ratios of breast cancer associated with classic risk factors as parity, lactation and age at first full term pregnancy did not show statistically significant differences in the three models, although the risk directions were as expected which could be explained by the small sample size of studied population. Oxford: Oxford Science Publications; Co-operation from those receiving such calls may be low. Lyon: International Agency for Research on Cancer; Random Digit Dialing Random digit dialing has been popular in the past, but it is becoming less useful because of the use of caller ID, answer machines, and a greater reliance on cell phones instead of land lines. Similarity of socio- economic characteristics and social behaviours have the same advantages and disadvantages as neighbourhood controls. Also, controls are likely to be similar to cases in respect of socio-economic factors.
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