Presentation on theme: "Hannah Hagan 91017622. Before new ideas are accepted by the medical profession they are put through trials to make sure that they are correct. There are."— Presentation transcript:
Before new ideas are accepted by the medical profession they are put through trials to make sure that they are correct. There are different types of trial, and each one has its own advantages and disadvantages. The best trials are designed so that the likelihood of the results being a coincidence is very small. The results of these trials are ‘stronger’ than the results of other trials The strongest types of trial are at the top of the pyramid, and the weakest are at the bottom
To reduce the likelihood that the results of a trial are due to chance: The results should be reproducible. This means that if you (or someone else) repeats the experiment, the results will be the same. There should be as few confounding factors as possible. A confounding factor is something that isn’t part of the study that affects the results. For example, in a study where you are looking at whether someone’s risk of heart disease is affected by their weight, if you don’t find out if they smoke or not, then smoking is a confounding factor because it can cause heart disease. There should be a different result in people who were treated with the new treatment compared to those who were treated with the old treatment. The image is a copyrighted image from the Arjan Dice website.
William Walwyn wrote a book in 1681 about his work. It described 80 cases where people were cured by his medicines. Interestingly, a lot of the people mentioned had already been treated by bleeding and purging, two common treatments of the day. The medicine described in the book could only be bought from Walwyn. Walwyn decided that medicine should be liquid, clear, pleasant and so good for you that it was impossible to overdose on. This was just his opinion. In his book, a lot of the people who got better had already been treated by doctors. The creator of the image is 88gugu88
In the late 1700’s George Pearson said that “ The testimony of a single observer, however experienced, and worthy to be credited, it is apprehended if insufficient for procuring such facts a general acceptance”. This was in response to Jenner’s work on cow-pox, which was just his observations and experimentation. This suggests that people were beginning to appreciate the reproducibility of experiments. This was the century that Dr Edward Jenner discovered that cow-pox prevented people from catching small pox. This was a case series study. William Woodville shared his method of inoculating patients with cow-pox. “I took the matter of cow-pox, in a purulent state, from the teats of a cow, with which I immediately inoculated seven persons by a single puncture in the arm of each, or rather by scratching the skin with the point of the lancet, till the instrument became tinged with blood.” This allowed others to copy his method and verify his results. The images are available at: http://commons.wikimedia.org/wiki/Edward_Jenner http://commons.wikimedia.org/wiki/File:George_Pearson_b1751.jpg
The Lancet, a respected medical journal, was established. This meant that doctors all over the country could access the latest information. It also meant that they could question research that had been done. Studies reported in this journal were similar to those published today. They included an introduction to the area, a methodology section, followed by their results and the limitations of their study. Images from: http://www.thelancetglobalhealthnetwork.com/about-us http://commons.wikimedia.org/wiki/File:Scalpel.png
In 1942 that the first medical randomised controlled trial was published. This revolutionised EBM. Previous trials were mainly useful when the new idea had a big, immediate impact, like when insulin was used in diabetes. The RCT allowed ideas that had smaller benefits (or harms) to be recognised. Today changes in medical practice almost always require a RCT; often changes are only made following the results of many RCTs. This is known as a meta-analysis and provides the strongest evidence. This image is the work of G. Terry Sharrer, Ph.d. National Museum Of American History.
1. Walwyn W, 1681. Physick for families: or, the new, safe and powerful way of physick, upon constant proof established, enabling everyone, at sea or land, by the medicines herein mentioned, to cure themselves, their friends and relations in all distempers and diseases. 2. Pearson G, 1798. An inquiry concerning the history of cowpox: prinicipally with a view to supercede and extinguish the samllpox. 3. Woodville W, 1799. Reports of a series of inoculations for the variolae vaccinae or cow pox: with remarks and observations on this disease considered as a substitute for the the smallpox. 4. The Lancet (1823-1824): MDCCCXXXII-IV. 5. Doll R, 1992. Sir Austin Bradford Hill and the progress of medical science. BMJ:305;pg 19-26 All images are copyright free unless otherwise noted.