An analysis of medical studies published on Blastocysts finds that medical researchers overwhelmingly have identified Blastocystis as disease causing. The study began by examining every Blastocystis paper indexed in the NIH's PubMed database before January 19, 2008. From an initial group of 680 studies, the research team identified 102 which met the criteria of the study - mainly, an abstract was available, and the researcher made a conclusion about Blastocystis' ability to cause disease following laboratory or clinical study. Of those 102 papers, 84% (86/102) identified Blastocystis as disease causing, while 16% (16/102) indicated that it did not cause disease.
"In this study, we took a hard look at whether there really is really controversy around Blastocystis, or whether medical professionals are using the term to evade their professional responsibility," noted study co-author Ken Boorom. The study was co-authored by 11 scientists from 9 countries. The authors included researchers who were working at the United States Center for Disease Control, China's Center for Disease Conrtol, the United States Air Force, the Pasteur Institute, a World Health Organization Collaborating Center for Parasitological Research, the Scottish Parasitology Laboratory, and additional public health labs in Thailand, Greece, and Turkey.
The study was published in BMC Parasites and Vectors. In addition to providing the final results, interested researchers can download and examine all the raw data used in the analysis, such as the list of 680 PubMed indexed studies, why each one was included or excluded, and a list of the 102 studies included in the final analysis.
Garbage In, Garbage Out
One of the most striking findings was that most of the studies identifying Blastocystis as harmless were published before 1994. When studies published in the last 15 years are considered, 95% of the researchers concluded Blastocystis was disease causing. "If there is a large group of people who are sure that Blastocystis is harmless, they aren't getting past the peer review process. We apparently have a medical system that is leaderless, and run mostly by armchair quartebacks," noted Boorom.
Why did the early studies have different conclusions? Blastocystis can be difficult to detect, and pathology laboratories were largely unregulated in the United States before 1993, when congress implemented the Clinical Laboratory Improvement Act (CLIA). The acts, were introduced to stop the creation of "laboratory sweatshops" where technicians were expected to analyze hundreds of samples per day. Before this, laboratory analysis could be performed in individuals without any formal training or testing, and the failure of one lab to properly identify cervical cancer cells caused the death of many women. Prior to CLIA, some physicians performed their infectious disease tests, and tests could also be performed by any nurse or staff member regardless of training. Because Blastocystis looks very similar to fat cells, or white blood cells, researchers may have been mis-reading samples.
"This is the largest study of this kind. This is the first time a group has systematically examined every study from a standard database like PubMed, and used that to examine consensus opinion in the medical research community" Boorom commented. Papers published in following years used more advanced methods for investigating the virulence of organisms, such as animal studies. Researchers publishing later papers may have had more reliable diagnostic services, since more Blastocystis photographs were published, and better diagnostic methods were developed. The study also found that none of the papers that contradicted Blastocystis as a pathogen were published by individuals identified as parasitologists. "That's like getting advice on HIV infection without asking a virologist." commented Boorom.
Boorom KF, Smith H, Nimri L, Viscogliosi E, Spanakos G, Parkar U, Li LH, Zhou XN, Ok UZ, Leelayoova S, Jones MS. Oh my aching gut: irritable bowel syndrome, Blastocystis, and asymptomatic infection. Parasit Vectors. 2008 Oct 21;1(1):40.PMID: 18937874