Local Coverage Article Response to Comments

Response to Comments: Multiplex Gastrointestinal Pathogen Panel (GPP) Tests for Acute Gastroenteritis (AGE)


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Response to Comments: Multiplex Gastrointestinal Pathogen Panel (GPP) Tests for Acute Gastroenteritis (AGE)
Article Type
Response to Comments
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As an important part of Medicare Local Coverage Determination (LCD) development, National Government Services solicits comments from the provider community and from members of the public who may be affected by or interested in our LCDs. The purpose of the advice and comment process is to gain the expertise and experience of those commenting.

We would like to thank those who suggested changes to the Multiplex Gastrointestinal Pathogen Panel (GPP) Tests for Acute Gastroenteritis (AGE). The official notice period for the final LCD begins on June 16, 2022 and the final determination will become effective on August 1, 2022.

Response To Comments


Laboratory Developed Test (LDT)- The College of American Pathologists (CAP) and Association for Molecular Pathology (AMP) submitted joint comments, including a recommendation to cover “high quality laboratory developed tests (LDTs) that are not FDA approved… when a test meets appropriate analytical and clinical validity (AV/CV) standards and fulfills the “reasonable and necessary” criteria as outlined in the proposed LCD.”

NGS agrees that LDTs may qualify, and the following language has been added: “Tests must be FDA approved/cleared, or if a laboratory developed test (LDT), have a published, peer-reviewed study supporting analytic validity, or certification by a third-party consistent with the New York State Department of Health’s Clinical Laboratory Evaluation Program (CLEP) review standards.”


≥6 stools per 24 hours- Another CAP/AMP recommendation was to delete the wording related to “passage of ≥6 unformed stools per 24 hours” associated with indication 1b, as too restrictive, and revise to ≥ 3 unformed stools per 24 hours.

The reference to ≥6 unformed stools per 24 hours was meant as an example of what might be seen in severe illness, not a requirement. The underlying definitional requirement is already ≥3 loose or watery stools/day. We’ve added “e.g.” to the referenced parenthetical list for clarity.


Repeat panel testing- CAP/AMP also recommended coverage of a second panel test “for the same clinical indication if the first panel yielded a negative result AND there is a high index of suspicion for a pathogen as the cause of symptoms, AND the patient’s clinical condition is not improving or is deteriorating, AND as long as the test fulfills the criteria for coverage set forth in the LCD.”

NGS agrees and has added the suggested language.


More than 72 hours after hospitalization- CAP/AMP requested “that the LCD language state clearly that NGS will not cover tests more than 72 hours after a patient is admitted to the hospital and is still an inpatient.”

NGS agrees and has modified the policy language accordingly.


Laxative in the prior 48 hours- CAP/AMP requested that “laxatives in the prior 48 hours” be struck as a contraindication. “AMP and CAP believe that the requirement stating that a patient must not have used laxatives prior to 48 hours of the test, is overly restrictive. Patients who utilize laxatives are still capable of contracting an infection, regardless of laxative use. Further, there are medications other than laxatives that may exacerbate normal bowel movements. This draft LCD requirement would have a negative impact on multiple patient groups; for example, those patients with Clostridioides difficile (C. diff).”

While NGS agrees that laxative use and infection are not mutually exclusive, it is also true that laxative use is cited as a potential confounding factor in result interpretation (1), even in the context of C. difficile (2). However, we will exempt those with signs of severe disease that may warrant hospitalization regardless of the prior use of laxatives.

  1. O'Neal M, Murray H, Dash S, Al-Hasan MN, Justo JA, Bookstaver PB. Evaluating appropriateness and diagnostic stewardship opportunities of multiplex polymerase chain reaction gastrointestinal testing within a hospital system. Ther Adv Infect Dis. 2020;7:2049936120959561.
  2. McDonald LC, Gerding DN, Johnson S, et al. Clinical Practice Guidelines for Clostridium difficile Infection in Adults and Children: 2017 Update by the Infectious Diseases Society of America (IDSA) and Society for Healthcare Epidemiology of America (SHEA). Clin Infect Dis. 2018;66(7):e1-e48.

Specialty/Place of service (POS)- CAP/AMP commented that the outpatient specialty requirements related to highly multiplexed GPPs were too restrictive, citing additional delay and cost. They recommend that the following language be added after “Testing is ordered by a clinician specialist in Infectious Diseases or Gastroenterology”: “or a healthcare guideline or algorithm with contribution of infectious disease or gastrointestinal specialist.” The medical director of bioMerieux made a similar case, noting: “Because acute gastroenteritis is not a condition generally requiring specialized treatment, patients seeking care for this condition are often seen by primary care physicians and physician extenders. Many facilities report successful use of multiplex gastrointestinal pathogen panel (GPP) tests for outpatient testing, ordered and interpreted by primary care providers and without an infectious disease (ID) specialist." This was echoed by the Mayo Clinic Director of Clinical Virology.

The draft LCD specialty restrictions only apply to highly multiplexed GPPs ordered in an outpatient setting. Only the CAP/AMP comment seemed to recognize that distinction and acknowledge the need for some type of added expertise. As noted in the LCD Analysis of Evidence section, NGS believes specialist involvement in selection and interpretation of highly multiplexed GPPs important for both individual patient care and overall antimicrobial stewardship. However, involvement can simply be documented communication with the ordering primary care physician. The outpatient specialist ordering requirement has been relaxed accordingly; this also obviates the need for the geographic exception. We feel reference to “a healthcare guideline or algorithm” to be too vague to be added.


Additional ICD-10 codes- CAP/AMP requested the addition of three ICD-10 codes to the Billing and Coding article (R19.7 Diarrhea, unspecified; R10.84 Generalized abdominal pain; and R11.2 Nausea with vomiting, unspecified). The Mayo Clinic Director of Clinical Virology requested R19.7 and A09 (infectious gastroenteritis and colitis).

NGS agrees that, in the absence of detection of a specific pathogen, ICD-10 code R19.7, Diarrhea unspecified, is appropriate, and it has been added. A09 was already listed. We disagree with the others as too nonspecific.

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