Talk:Case–control study

Untitled
Banner at the top is distracting, can we remove this? — Preceding unsigned comment added by 75.151.248.161 (talk) 16:07, 27 November 2012 (UTC)

OR and RR
In the figure (ExplainingCaseControlSJW.jpg) the terms RR and OR are not defined. What do they stand for? They should be defined in the figure legend. — Preceding unsigned comment added by 144.30.70.195 (talk) 15:53, 26 September 2011 (UTC)


 * I'm sceptical to the claim that "odds ratio [...] is an inferior measure of strength of association compared to relative risk". Relative risk (RR = p2/p1), odds ratio (OR = (p2/(1-p2))/(p1/(1-p1)) and hazard ratio (HR = log(p2)/log(p1)) are all different ways of expressing the contrast between two probabilities, and they all have different properties. [If anything, I would say that HR is more meaningful whenever it makes sense to talk about hazard rates (i.e. when p = exp(-{integrated hazard rate oven an interval}) as HR is then invariant to the length of the interval as long as the two hazard rates remain proportional in the interval. RR is certainly not invariant to conditioning (background conditions). It may (at least sometimes) be easier to argue that OR an HR could be approximately invariant to conditioning - see https://doi.org/10.1111/2041-210X.13059]. I suggest removing this. --Torbjørn Ergon (talk) 12:22, 16 April 2021 (UTC)


 * Might any of you know of a solid reference to support the claim at the end of the lede that, "A case–control study produces only an odds ratio, which is an inferior measure of strength of association compared to relative risk"?
 * User:Torbjørn Ergon and I are skeptical; see User:Torbjørn Ergon's comments above.
 * User:Torbjørn Ergon and I are skeptical; see User:Torbjørn Ergon's comments above.


 * I"m also skeptical of the claim that Greenhouse said that Cornfield "pointed out that, when the disease outcome of interest is rare, the odds ratio of exposure can be used to estimate the relative risk".
 * I'm skeptical, because I think this is sloppy and imprecise language, when it's accurate, clearer, and more precise to say that "the odds ratio of exposure can be used to estimate the relative risk" when the disease outcome is rare.


 * Jerome Cornfield and Samuel Greenhouse were both leading statisticians of the twentieth century and highly credible, in my judgment. If this is an exact quote, then it should be stated as such.  Otherwise, I recommend we replace it with something that's more precise, like what I wrote.


 * To explain this comparison of OR and RR when the disease outcome is rare, I will use the Big O notation. When $$p$$ is small, $$p/(1-p) = p[1+O(p)]$$, and similarly:


 * OR = $$(p_2/(1-p_2))/(p_1/(1-p_1)$$
 * = $$(p_2/p_1)(1-p_1)/(1-p_2)$$
 * = RR$$[1-p_1+O(p_2)]\quad\text{ as }p_i\to 0$$


 * I'm similarly skeptical the summary box: 360px|thumb|upright=1|Case–control study versus cohort on a timeline. "OR" stands for "odds ratio" and "RR" stands for "relative risk".


 * In particular, if we want to claim that either OR or RR is better for certain uses than the other, I want to see the math explaining why and a solid, credible reference.


 * Without that, I recommend we delete that box and any other references that say that either OR or RR is better than the other: I may be true that one tends to be used more in a certain context,


 * FYI: One key reference is ?
 * Unless someone has easy access to this and other references, I suggest we try Resource Request(s) from The Wikipedia Library.
 * If you want to look at a book, you might try an "Advanced Search" for "Mediatypes is texts" for the title and maybe author you want via archive.org (the Internet Archive).


 * Thanks to User:Torbjørn Ergon for questioning this. DavidMCEddy (talk) 13:57, 16 April 2021 (UTC)

Untitled
study but rather a cohort study. In the cohort study the time evolution of a large group of people (in that case doctors) is studied from time zero into the future and the number of lung cancers is recorded both for smokers and non-smokers. In the case-control one would take a sample of sick people (cases) and healthy people (controls) and then compare the fraction of past smokers and non smokers in the two samples. Cohort studies and case-control studies are fundamentally different even if in the cohort there are "controls". So I think that the reference to Doll's study here is misleading.


 * You mean like this?
 * ''Sir Richard and his colleagues interviewed 700 lung cancer patients to try to identify a possible link.
 * ''"We asked them every question we could think of," he said.
 * "It wasn't long before it became clear that cigarette smoking may be to blame. Gzuckier (talk) 15:11, 16 May 2008 (UTC)


 * If I remember correctly, Doll and colleagues started by just asking lung cancer sufferers everything they could think of - traffic fumes were one of the original ideas - and used that to generate some hypotheses worth testing by a case-control study. They then tested their conclusions about cigarette smoke further with a cohort study, much more expensive and time-consuming but less liable to bias, and further by looking within that cohort study at the risk to subjects who gave up smoking. The latter finding, that those who gave up smoking had a risk of lung cancer that declined to nonsmokers' levels over 15 years or so, was and is thought to give the strongest evidence. It may not be a trial, but it is very difficult to see how it could give a result biased in this particular way. Richard Keatinge (talk) 10:28, 17 May 2008 (UTC)

Mokgand 18:34, 14 August 2005 (UTC) Some sectioning and structure could be helpful. Mokgand 20:05, 14 August 2005 (UTC) The triumph of case control in establishing the health effects of tobacco is mentioned. I have heard that there are examples of cases where case control studies are said (npov :-) to have given misleading results. See :


 * Conflicting evidence - a concern not only for cycle helmet research
 * Estrogen plus Progestin and the Risk of Coronary Heart Disease by JoAnn E. Manso et al in New England Journal of Medicine (Volume 349:523-534 August 7, 2003 Number 6)

I admit to not having read this last one, but it is cited by ''Commentary; Hormone replacement therapy and coronary heart disease: four lessons. Pettiti D. Int Jour Epid 2004;33:461-3'', which again is cited by the cyclehelmets article.

The Lawlor et al. commentary referenced in the Strengths and Weaknesses section discusses a meta-analysis that is not solely of case-control studies, and that indeed "inferred a relative reduction," i.e., a reduction in relative risk, for the exposure (a measure unobtainable in case-control studies themselves, as the panel on this page's upper right notes). Perhaps the Lawlor citation does not belong on this page. Mucketymuck (talk) 14:59, 14 May 2019 (UTC)

Error - I'm pretty sure Doll never won the Nobel prize! Blaise 20:53, September 1, 2005 (UTC)
 * So who is Doll, and what reasons do you have for saying so ?  --85.220.120.207 22:19, 3 September 2005 (UTC)


 * Doll is Sir Richard_Doll. He is not listed among Nobel Laurates in Medicine. --Moklevat 18:36, 19 September 2005 (UTC)


 * I believe you may be correct - should the reference be edited out? Just zis Guy, you know? 09:31, 5 October 2005 (UTC)

Folks, I have added a bit of structure and some commentary on confounding and the Lawlor and Pettiti articles (which I have read), also on a recent study whose cite escapes me (I will find and add) which shows that a majority of highly-cited case-control studies are subsequently contradicted by other evidence. I have tried to do this in a balanced way, reflecting the fact that case-control is still considered valuable evidence despite recent controversies. Hope it's OK. Just zis Guy, you know? 15:41, 4 October 2005 (UTC)

The part about the effectiveness about seat belts and cycle helmets is clearly controversial and should be rewritten, either by choosing non-controversial examples of confounding factors or by adding a statement that these examples are still controversial among the experts. At the very least citations should be added for the claims made. F91jsw 09:10, 1 February 2007 (UTC)

Merge
There has been a merger proposed with Case-controlled trial for some months. Opinions? Merge or remove the tag? Tedernst 18:58, 2 November 2005 (UTC)
 * I don't think there's much to merge, is there anything in Case-controlled trial which is not already here? A redirect may well be sufficient. - Just zis Guy, you know? [T]/[C] 19:36, 2 November 2005 (UTC)
 * Fair enough. I'll dump the text in as if merging and then in a seperate edit will delete out everything that seems to duplicate what's already here.  Could be there will be nothing left at that point. Tedernst 20:54, 2 November 2005 (UTC)

--Browser 18:45, 24 August 2006 (UTC) In reference to smoking 'the eventual results of double-blind prospective studies confirmed the causal link' seems unlikely. How can you have a double-blind study on smoking - double blind means the patient does not know what is happening, but you can't smoke without noticing. Is there a subtlety, like the trials being on high- and low-tar cigarettes where the patient was unaware which was which, or is this just plain wrong?

Rename: Case control study
Wouldn't case control study be a better name for this page? --jwandersTalk 00:12, 9 February 2008 (UTC)

POV?
No, in medical literature case-control is the way this type of study is commonly referred to; not case control —Preceding unsigned comment added by 198.54.202.102 (talk) 12:57, 16 May 2008 (UTC)

The sentence in the first paragraph about "led some to doubt their credibility" sounds POV —Preceding unsigned comment added by 207.181.213.101 (talk) 05:28, 10 April 2008 (UTC)

Cleanup
I just edited this page: I didn't have time to change everything I thought ought to be changed, but I will try to add to this in future, as the quality of this page was simply terrible. (I do have a background in epidemiology, so I thought I would help out a bit with these pages. :-) Alic D (talk) 00:38, 3 August 2011 (UTC)

--161.136.212.150 (talk) 19:25, 2 July 2008 (UTC) This entry is pretty horrible. It really doesn't explain the methodology. It makes some confusing claims about cross-sectional studies, and acts as if all "real" studies were clinical trials. Trials are a specific kind of experiment, and experiments only make sense when there are factors you can reasonably vary and apply random assignment to. There is no discussion in the article about "exposure", which is a central concept, and the discussion about how to analyze case-control studies is just wrong. I did a little bit of editing, but I don't have the time (or knowledge) to make it right. --Somewhat Agree (talk) 19:26, 2 July 2008 (UTC)

Gtakanis (talk) 11:26, 17 March 2008 (UTC) The study by Doll and Bradford on tobacco and lung cancer is not a case-control

Correlation and causation references
I know this is not in protocol, but case control studies cannot show causation. This article says so twice without citation. It is misleading. Also, using tobacco and lung cancer is leading, a less biased example would better explain this type of research design. — Preceding unsigned comment added by 69.255.42.109 (talk) 03:57, 18 November 2011 (UTC)

The British Doctors Study was not a case control study, but a cohort study.. no?
I'm pretty sure of this, and googling the terms seem to suggest the same, maybe some one could verify it and paste the smoking paragraphs over to the cohort study page. — Preceding unsigned comment added by 86.194.80.44 (talk) 08:20, 27 December 2011 (UTC)

It is a case control study, a very famous one so I'm not sure why it has been misattributed here. (How to read a paper 4th ed Trisha Greenhalgh 2011 pp40-41) — Preceding unsigned comment added by 151.227.254.133 (talk) 19:38, 16 December 2014 (UTC)


 * Doll and Bradford Hill's preliminary study, not of doctors, was case-control, see https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2038856/pdf/brmedj03566-0003.pdf. The much larger British Doctors Study, perhaps most conveniently summarized by https://www.ncbi.nlm.nih.gov/pmc/articles/PMC437139/ was a oohort study. I hope this helps. Richard Keatinge (talk) 22:00, 16 December 2014 (UTC)

Fix grammar
Should be using en-dash in "case–control". —DIV (137.111.13.4 (talk) 08:06, 24 January 2014 (UTC))

POV about risk ratio vs. odds ratio
Hi. The article currently states "A case–control study is often used to produce an odds ratio, which is an inferior measure of strength of association compared to relative risk" (bold is mine). The statement in bold is controversial, so this statement violates WP:NPOV. See https://www.jclinepi.com/article/S0895-4356(20)31171-9/fulltext for example of a source disputing that risk ratio is a measure superior to odds ratio. So this part of the sentence should be rewritten, or entirely removed. 147.94.11.173 (talk) 08:35, 15 January 2024 (UTC)
 * I simply removed the statement. 147.94.11.173 (talk) 14:18, 15 January 2024 (UTC)