Clinical trials rarely have a second look, and when they do, their results are not always what the original authors reported. This is the conclusion of a new study, which compared how 37 studies that had been measured reanalyzed the original. In 13 cases, reanalysis came to a result-a different conclusion suggests that many clinical trials may not be accurately reported the effect of a new drug or intervention.
To conduct the study, published today in on Journal of the American Medical Association ( JAMA ), Shanil Ebrahim, a clinical epidemiologist at the school of medicine at Stanford University in Palo Alto, California, and colleagues combed through the MEDLINE database. The online archive contains nearly every life sciences and biomedical research studies conducted over the past 64 years. The team found 37 trials that were retested. Of these, 13 have come to contradictory conclusions with the findings of the original author. Moreover, only five were reanalyses by a set quite different authors, which means they do not get a neutral relook.
In one of the trials that examined the efficacy of methotrexate drug in the treatment of systemic sclerosis autoimmune disease that causes -a healing of the skin and internal organs, the original researchers found that the drug is no more effective than placebo, as they reported in a 01 paper However, in a reanalysis of the same trial in 09, another group of researchers, one of the original authors used Bayesian analysis a statistical technique to overcome the shortcomings of small data sets that plague clinical trials of rare diseases such as multiple. Reanalysis found that the drug was as it appeared more effective than placebo and had a good chance to benefit multiple sclerosis patients.
In another study, researchers re-analyze a 1984 clinical trial of sclerotherapy in which a drug is injected to treat enlarged veins in the esophagus. The original researchers found that the therapy reduces mortality, but did not reduce the risk of recurrent bleeding at a later date. Based on this finding, they recommended sclerotherapy patients. In 01, however, another group of researchers analyzed the same data with a different statistical method which examined the interaction between recurrent bleeding and mortality, and concluded that sclerotherapy does not reduce mortality. Their results imply that doctors should avoid prescribing sclerotherapy in patients with a high risk of mortality, in contrast to the initial conclusion. Sclerotherapy is still commonly used for the treatment of hemorrhoids and varicose veins.
Other reanalysis found fault with the original methodology. For example, in a study on the effectiveness of the mechanical cardiopulmonary resuscitation (CPR) compared to manual CPR in patients with cardiac arrest outside the hospital, one of the hospitals participating in the trial changed halfway protocols. This changed the outcome of the trial in favor of manual CPR, a flaw that the corrected reanalysis. The authors of this reanalysis belonged to the same research group that the original study.
"It is alarming that an important part of testing came to different conclusions," said Ebrahim. While reanalysis does not always mean the original research was flawed, the amended findings indicate a greater need for sharing clinical trial data, he said.
Tom Jefferson, a researcher based in Rome, which reviews the studies for the Cochrane Collaboration nonprofit, says the results of JAMA study does not surprise. "The process [of analyzing clinical trials] is so subjective, you can twist it as you wish." He noted that pharmaceutical companies often do not provide the all-important raw data from clinical trials, instead of choosing to publish summaries highly compressed their results.
last year, the Cochrane Collaboration has succeeded in a 4-year battle with the Swiss pharmaceutical giant Roche to access raw data from unpublished clinical trials of its drug against the flu Tamiflu. governments around the world were stored drugs to protect against a flu epidemic, after clinical trials found the drug to be effective in the disease. But during a re-analysis of these trials, Cochrane Collaboration found that the underlying raw data of several published studies had not been released. When he finally was able to access this data many years later, a re-analysis showed that Tamiflu was not as effective as thought earlier.
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