Stool Tools: PCR Detection of Astrovirus and Sapovirus

Abstract

FV is an 80 year-old woman with past medical history significant for hypertension, a partial colectomy for ischemic colitis, rheumatoid arthritis, pancreatic insufficiency, and coronary artery disease who had initially presented to her outpatient Gastroenterology follow-up reporting weight loss, constipation, and with continued iron-deficiency anemia. Ultimately, EGD and colonoscopy performed in November 2016 demonstrated only diverticulosis and internal hemorrhoids and pathology results from duodenal and gastric biopsies were unremarkable. In February 2017, she had presented to the Emergency Department complaining of 1 week's duration of diarrhea that was not initially bloody though did have some blood with her last bowel movements prior to presentation. A CT scan of the abdomen revealed no obstruction and no bowel wall thickening. The PCR pathogen panel resulted detection of both astrovirus and sapovirus and other laboratory values for the patient, apart from her baseline anemia, were unremarkable. Upon treatment with loperamide, the patient's diarrhea improved and she was discharged soon after presentation. Acute gastroenteritis (AGE) is characterized by the sudden onset of diarrhea, nausea, vomiting, and abdominal pain. Viruses are certainly the most common known agents of AGE and noroviruses, more specifically, have been estimated to cause 19-21 million cases of AGE per year. Viruses including rotavirus, astrovirus, and sapovirus have also been implicated in cases of AGE but more notably, among children. There seems to be little literature on the prevalence of astrovirus and sapovirus among the other AGE-causing viruses. Conventional diagnosis for such viruses has, in the past, been based on direct antigen detection and electron microscopy though enzyme immunoassays appear to be insensitive and not readily available for all relevant pathogens. Now, however, with the advent of single multiplex PCR testing, it has become easier to detect such pathogens. In fact, most laboratories now include real-time PCR testing as the gold standard for norovirus detection given poor performance of EIA and other assays in detecting the virus. Given use of the pathogen PCR panel, we may ultimately have more information surrounding the incidence and prevalence of astrovirus as well as sapovirus infection. Given this we will be able to glean more information surrounding the natural course of such viruses and the clinical significance infection with them bears.