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February 21, 2005
Genetic blood test for sz?
Assessing the Validity of Blood-Based Gene Expression Profiles for the Classification of Schizophrenia and Bipolar Disorder: A Preliminary Report
Ming T. Tsuang, Nadine Nossova, Tom Yager, Min-Min Tsuang, Shi-Chin Guo, Kou Ge Shyu, Stephen J. Glatt, and C.C. Liew
American Journal of Medical Genetics Part B (Neuropsychiatric Genetics) 133B:1–5 (2005)
In this paper, the authors are describing a new technique for doing genetic testing. Traditionally, DNA tests are done on tissues, particularly the tissue that shows evidence of the disease being queried. In psychiatric illness however, that is difficult or impossible because one cannot do a brain biopsy without significant risk of harm to the patient. It has been hypothesized that blood may be a “sentinel” marker for disease in the body. That means that if there is a problem somewhere in the body, it may show evidence in the blood in addition to the location where the problem has occurred. Using blood is helpful also because there is a large supply in the body, it is reproduced rapidly so multiple samples are possible, and it is easy and safe to obtain with little pain or risk to the patient. These authors specifically were looking at RNA in the blood to help differentiate between people with bipolar disorder, schizophrenia and the normal population.
This study showed some very exciting and interesting results. While it is limited by a small sample size and a very homogenous population, the possibilities raised by this work are significant. They were able to look at a large number of genes, including many that would not have been thought to have a relation to schizophrenia. They used an “unbiased” approach which utilized a more wide ranging view to look for potential markers. They found that they could differentiate between schizophrenia and bipolar and healthy control with approximately 95% reliability. One of the major markers noted in schizophrenia had to do with genes that are turned on in inflammatory diseases (like rheumatoid arthritis, cystic fibrosis and myocarditis.) This may mean that schizophrenia has an inflammatory component that was not previously considered important to the mechanism.
This study, while interesting and potentially significant, does have several caveats that need to be remembered. It was a small study that looked at 74 patients (30 with schizophrenia, 16 with bipolar disorder and 28 healthy controls.) All of the patients were of Han Chinese descent and were inpatients in Taiwan. It is possible that this population has unique genetic characteristics that were being picked up, though they were compared with people of similar descent and in a similar location in the world. Also, all of the patients were undergoing treatment with antipsychotics. It is possible that the medications were causing some of the changes noted in the blood and that could account for some of the difference between schizophrenia patients and healthy controls. Antipsychotics for example, may have a small pro-inflammatory effect which could cause the inflammatory markers to be positive perhaps. Larger studied, with more diverse population and preferable people who are naïve to antipsychotic medication would be ideal to study and could give a more clear answer to the questions being asked by the authors. However, it is still an important finding and worthy of future research to help identify potential markers in blood to assist in the diagnosis and genetic prediction for schizophrenia and bipolar disorder.Posted by Jacob at February 21, 2005 07:55 PM