In Star Trek, Dr. Leonard McCoy used a medical tricorder to effortlessly diagnose a lot of conditions (Tricorder – Wikipedia, the free encyclopedia, Medical tricorder – Wikipedia, the free encyclopedia). While many of the newest diagnostic tests are not as portable, they share a feature of being able to diagnose a wide range of conditions quickly. These tests include imaging studies like MRI and CT, genetic microarrays, and now PCR panels to diagnose a broad array of respiratory and gastrointestinal ailments.
One of the newest is the “xTAG GPP.” With one stool sample, this Gastrointestinal Pathogen Panel (GPP) can detect at least 11 common bacteria, viral, and parasitic pathogens in about five hours. Thus, all patients with identifiable gastroenteritis illnesses can be diagnosed more quickly. The test relies on a “multiplex nucleic acid test.”
FDA News Release Jan 15, 2013 (Press Announcements > FDA permits marketing of first test that can …):
“Infectious gastroenteritis is an inflammation of the stomach and intestines caused by certain viruses, bacteria, or parasites. Common symptoms include vomiting and diarrhea, which can be more severe in infants, the elderly, and people with suppressed immune systems. Gastroenteritis can be spread easily through person-to-person contact and contaminated food, water, and surfaces.
The Centers for Disease Control and Prevention reports that between 1999 and 2007 gastroenteritis-associated deaths in the United States increased from nearly 7,000 to more than 17,000 per year. Norovirus and Clostridium difficile accounted for two-thirds of the deaths.
The xTAG Gastrointestinal Pathogen Panel (GPP), a multiplexed nucleic acid test, detects the following causes of gastroenteritis:
- Clostridium difficile (C. difficile) toxin A/B
- Escherichia coli (E. coli) O157
- Enterotoxigenic Escherichia coli (ETEC) LT/ST
- Shiga‐like Toxin producing E. coli (STEC) stx 1/stx 2
“Tests such as the XTag GPP that can detect viruses, bacteria, and parasites from one sample at the same time can help clinicians more quickly identify and treat what’s causing gastroenteritis,” said Alberto Gutierrez, Ph.D., director of the Office of In Vitro Diagnostics and Radiology at the FDA’s Center for Devices and Radiological Health. “The test could also allow clinicians and public health professionals to more quickly identify and investigate the source of potential gastroenteritis outbreaks.”
The manufacturer demonstrated the performance of the xTAG GPP by collecting samples from 1,407 patients with suspected infectious gastroenteritis and comparing the xTAG GPP results to individual tests that are known to separately and reliably detect the 11 viruses, bacteria, or parasites associated with the xTAG GPP. The manufacturer also ran the test on 203 samples from patients with previously confirmed infectious gastroenteritis, and 313 additional specimens from pediatric patients with suspected infectious gastroenteritis. Results were comparable to the individual tests. Due to the risk of false positives, all positive results from the xTAG GPP need to be confirmed by additional testing (blog entry underlined for emphasis, not in original FDA release).
Luminex, Inc., of Austin, Texas, manufactures the xTAG.”
According to manufacter’s website, the test also detects Yersinia, Entamoeba histolytica, and adenovirus. It reports sensitivity of of >94% for almost all pathogens (except Salmonella which was 84%) and specificity of >94% for all of the pathogens.