Matched Pair Case-Control Study

Transcription

1 Matched Pair Case-Control Study Pairs of Cases and Controls matched 1:1 on defined characteristics are evaluated for exposure to a risk factor and distributed into the four cells of the table representing the four possible combinations of outcome in a pair. The counts represent PAIRS containing 1 case and 1 control rather than individual cases. Results include Fisher Exact and midp Exact tests and confidence limits for the odds ratio, and the McNemar test and the Pair-Matched Odds Ratio to evaluate whether an association exists between case status and the presence or absence of the risk factor. Autores Statistics Kevin M. Sullivan, Emory University based on code from John C. Pezzullo Interface Andrew G. Dean, EpiInformatics.com, and Roger Mir Seleccione, copie, y pegue los resultados a otros programas o baje OpenEpi al disco local y ejecute OpenEpiSave.HTA para guardar automáticamente.

2 Using OpenEpi Uso de OpenEpi From the Web or On Your Desktop From the Web Point your browser to Choose a program, enter data or load demo data (if available), then click Calculate to see the results Select all or part of the results by clicking and dragging with the mouse. Ctrl-C or Edit Copy will copy to the clipboard Ctrl-V or Edit Paste in another program, such as Word or Excel Download the Entire Site to Your Desktop Choose Download from the menu Choose either the minimal system (<1 meg) or the entire site(about 5 meg.) Save the zip file or open it from the web Unzip and leave the files in the same relative directories Click on Index.htm, run it from the browser, or execute it from Start run Create a desktop icon for future use, using (in Windows) right-click and Send to Desktop Choosing a Statistical Method If you are not sure which module to use or want further information, use the Choosing a Method entry on the menu Find the type of data you have and see what methods are appropriate

3 Each cell in the table will perform an on-line search using Google.com when you click on the text Entering Data In any application, choose Enter New Data to enter your own data or Load Demo Data for one of the samples described in the Exercises link If asked, give the number of columns or rows needed Use either the Enter or Tab keys, and the up and down arrow keys to move around. Movement is across the screen until the down-arrow is pressed, then vertically until the first mouse-click. To enter labels, variable names, or values, click on a cell and respond affirmatively to the message Saving Results For Windows users, a special program called OpenEpiSave.hta is provided When you run OpenEpiSave.hta from your hard disk, it will bring up OpenEpiMenu in your browser The output of each program will be saved in the Results directory as an HTML file, and a notice will display briefly each time a file is saved Checking with Other Programs When you get that final call-stockholm kind of result in OpenEpi (or any program), take the time to repeat the analysis in another program. There are hundreds of other calculators in a link on the menu, or use SAS, SPSS, or Epi Info If the results differ, let us know. If the results do not differ, also let us know! We want to build the validation files. Enjoy and Communicate We hope you enjoy using OpenEpi Send us feedback with suggestions, wishes, or problems If you would like to develop a program, check the developer s section of the menu, and also send us an

4 MatchCC--Demo The default numbers presented are from a comparison of detection of hypertension by an automatic device versus detection by a trained technician. The automatic device results are 'Cases' and the technician s results are the 'Controls'. Click Calculate to discover (with the mid-p exact) that the difference may be marginally significant with this unrealistically small sample. More results are needed. Data from Rosner, B Fundamentals of Biostatistics, 5th ed., Duxbury, 2000, p More Exercises 183 cases of endometrial cancer were compared with the same number of controls matched by age, race, date of admission, and hospital. The factor of interest was previous exposure to oral estrogen (conjugated estrogens). There were 12 pairs in which both case and control were exposed, and 121 pairs in which neither was exposed. Discordant pairs included 7 with unexposed case and exposed control and 43 with exposed case and unexposed control. Find the odds ratio and compare it with the odds ratio using the unmatched methods of TwobyTwo analysis, which gave an odds ratio of Did the matching make a difference?

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