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Pⁿ Blog
The Pⁿ Blog is a forum for opinions, questions, controversies, and instructive discussions across the field of pathology and its relevant subspecialties.
Friday, January 03, 2014
The (DNA) Crystal Ball is Cloudy.
I hope that everyone had an enjoyable holiday season and has a happy new year.
Genetic testing is becoming quite a rage, at least in certain demographic segments of the population.  Magazines and even television advertisements market these products.  Take a buccal swab from yourself or your dog and you can find out your (or your dog's) lineage.  Take another one from yourself, mail it off to a the right lab and, at least according to the advertising hype, you can find out your risk for all sorts of diseases.  Sound too good to be true?  Well, at least for now it IS too good to be true.  I would refer you to a very interesting article in the December 30th issue of the New York Times entitled, "I had my DNA picture taken with varying results."
The author, Kira Peikoff is a 28-year-old writer who decided to send DNA specimens to three labs that claimed to provide disease risk analysis on the basis of a DNA sample.  The specimens went to 23andMe, Genetic Testing Laboratories, and Pathway Genomics.  The results were quite enlightening, in an unexpected way, and perhaps not too dissimilar from visiting several fortune tellers or palm readers with diverse crystal balls or tea leaves.  As just one example of the divergence of findings, 23andMe indicated elevated risks compared to the general population for psoriasis and rheumatoid arthritis, while Genetic Testing Laboratories indicated the lowest risk for exactly these two diseases!
It's clear that whole genome sequencing could give anyone a LOT of information about genetic predispositions, although even there good controls do not exist and the role of nature v. nuture is complex for many disease entities.  However, these marketed tests are looking at only single-nucleotide polymorphisms (SNPs), and often not the same SNPs for each disease predilection.  As Dr. Robert Klitzman points out in the article, this is like trying to understand a book by reading the first letter on each page.
This is an area that isn't going to go away and is one that the FDA is increasingly concerned about. 23andMe received a strong warning from the FDA regarding concerns about the accuracy of its testing system.  Pathway was blocked by the FDA from selling its DNA kits in Wahlgrens.  Class action suits have been filed against several companies for allegedly meaningless results.  
Ms. Peikoff's article is a short and enjoyable read.  I recommend it.  By the way, even though human disease risk prediction based on SNPs is a total crap shoot, at least at the moment, the pet lineage testing works rather well if you want to know what went into the makeup of your mongrel.  Human lineage testing is also reported to work reasonably well. 
About the Author

Stacey E. Mills, MD
Stacey E. Mills, MD, a graduate of University of Virginia (UVA) and the UVA Medical Center, has authored nearly 230 articles, 20+ books, atlases and monographs—including the renowned Sternberg's Diagnostic Surgical Pathology. He has been a practicing Professor and Staff Pathologist at UVA for 30+ years and is Director of Surgical Pathology and Cytopathology. His clinical specialty is general surgical pathology with emphasis on neoplasms and neoplasm-like lesions. Dr. Mills is also Editor-in-Chief of The American Journal of Surgical Pathology.