Stool Testing With Molecular Assay to Minimize Contact Precautions
Condition: Infectious Gastroenteritis
MeSH terms: Gastroenteritis
Study type: Interventional

Summary: 
      This study evaluates the impact of infectious diseases molecular-based stool testing compared
      to conventional stool testing on reducing the need for contact precautions among hospitalized
      patients. Half of patients' stools will be tested with the molecular assay , while the other
      half will be tested with conventional testing.
    

Detailed description: 
      Acute infectious gastroenteritis can be caused by viruses, bacteria or parasites, resulting
      in a diarrheal illness that may be accompanied by fever, abdominal pain and/or cramping,
      hematochezia, nausea, and vomiting. Up to 12.5% to 25% of the population develop a
      gastrointestinal infection each year, with the majority of cases being self-limiting and
      symptoms usually resolving within 14 days without treatment. While the vast majority of the
      estimated 4 million Canadians who develop gastroenteritis have a mild and self-limited
      illness, approximately 9 250 to 14 150 are hospitalized each year with 1.6% to 2.2% dying
      from their disease.

      For hospitalized patients, the majority will have stool samples collected and tested using
      standard microbiology methods that includes culture for bacteria, nucleic acid amplification
      for viruses and bacteria and microscopy or enzyme immunoassays for parasites. The number of
      pathogens that can be identified is limited in most microbiology laboratories, and the
      turnaround time to reporting can take up to 3 days. Recently, new nucleic acid amplification
      technologies have been developed that can test for multiple gastrointestinal pathogens in a
      single run that usually takes less than a 1 day turnaround time to reporting.

      The BioFire® FilmArray Gastrointestinal Panel (FGP) is a multiplex polymerase chain reaction
      test that can simultaneously test for 22 different viruses, bacteria and parasites with
      excellent sensitivity and specificity with a turnaround time of 1 hour. Compared to
      conventional testing methods, the FGP costs 40% more, or about $180 (CDN) per test. Despite
      detecting more pathogens in a shorter period of time, a recent systematic review did not find
      any evidence to support a positive impact on either improved patient outcomes or
      cost-effectiveness compared to conventional testing. Since most gastrointestinal illness
      episodes are mild and self-limiting, it may not be feasible to design a randomised trial to
      demonstrate clinical efficacy of test-treatment given the majority of the 22 pathogens
      detected by the FGP do not benefit from antimicrobial therapy. Instead, measuring other
      outcomes like reduced utilization of hospital resources such as contact isolation days, could
      provide evidence for both clinical benefit and cost-effectiveness.

      To date, the available evidence on the cost-effectiveness of the FGP assay has been based
      largely on observational studies, usually historically controlled before-after designs
      associated with high risk of bias. The only study that was of sufficient quality to be
      included in a systematic review of cost-effectiveness utilized a different PCR-based test.
      Since the FGP assay has been shown to have very similar diagnostic characteristics in a
      head-to-head comparison with this other PCR-based assay, the results will be used to inform
      the primary outcome for this study. In the study by Goldenberg et al., differences in contact
      isolation days between conventional (observed) and PCR-based testing (simulated) were
      estimated and found to result in a reduction of 34.3% in contact isolation days in the
      PCR-based group. Among the 800 patients, this amounted to a mean reduction of 0.94 contact
      isolation days per patient. Unfortunately, confidence intervals were not estimated for this
      point estimate. The cost of a single isolation day was reported as approximately £88 (UK) for
      fiscal 2011/2012. A breakeven analysis demonstrated that a reduction of 252 contact isolation
      days, a reduction of 11.4%, was needed to offset the increased costs associated with the
      PCR-based assay. The cost of the PCR-based assay used in this study was 0.4 times the cost of
      the FGP assay, suggesting that the number of contact isolation days needed to breakeven with
      the FGP assay could be as high as 635. In a more recent conference report of a randomised
      study in the United Kingdom using FGP, an interim analysis estimated a reduction in contact
      isolation days by 0.9 days per patient (95% CI 0.4 to 1.6). There was no data provided for
      cost-effectiveness. Given the extent of uncertainty around both the clinical effectiveness
      and cost-effectiveness of the FGP assay, a randomised test-treat trial would be the best
      option to resolve these uncertainties.
    

Intervention name(s): Conventional Stool Testing; BioFire FilmArray Gastrointestinal Panel
Intervention type(s): Diagnostic Test; Diagnostic Test
Intervention description(s): Stools are tested using conventional culture techniques; Molecular-based stool assay
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
Primary purpose: Health Services Research