Interpreting the GI Pathogen Plus Profile (GPP) Report · Interpreting the DRG GPP report Fecal fat Values over 400 are indicative of fat malabsorption syndromes that lead to steatorrhea

Interpreting theGI Pathogen Plus Profile

(GPP) ReportBernadette M. Mandes Wildemore, MD

Medical and Laboratory Director

DRG Laboratory

All tests were developed and their performance characteristics determined by DRG Laboratory

Diagnosis and treatment are the responsibility of the ordering physician

Interpreting the DRG GPP report

All testing at DRG is performed via molecular methods

Polymerase Chain Reaction (PCR)

Enzyme Linked Immuno-sorbent Assay (ELISA)

Sections of the GPP Report

Bacteria and Toxins by PCR

Antibiotic Resistance by PCR

GI Health Markers

Parasites by PCR

Fungi by PCR

Each of the analytes are listed by name on the left of the report

The quantitative value is listed for each analyte in the column labeled

‘Quantitation’

The result is listed for each analyte in the column labeled ‘Result’


It is imperative that the ordering clinician work in concert with the

laboratory values as provided by DRG. As our laboratorians do not

actually SEE the patient, it is critical for the treating physician to be

familiar and comfortable with the lab values we provide. Consultation

with our laboratory medicine specialists are always available if

questions arise

Result interpretation for Bacteria and Toxins section of GPP

For most of the values in the ‘Bacteria and Toxins by PCR’ section of the

report, DRG has determined the ‘cut-off’ or ‘nominal’ value as ≥ to 350

In other words, 350 is where the value turns from negative to positive

The exceptions include the Helicobacter pylori (HP) markers and the HP

stool antigen (please see later slides)

Interpreting the GPP ‘line by line’

First, let’s start with the Bacteria and Toxins by PCR section

Interpreting the GPP

Clostridium difficile (toxins A and B)

Bacterium that can cause significant diarrhea and colitis (≥3 loose stools in 24 hours)

Complaints usually associated with current or recent antibiotic therapy

Usually accompany treatment with

Fluoroquinolone

Clindamycin

Cephalosporin

Penicillin

BUT can be tied to any antibiotic use

Particularly of concern in very young or very old, or immunocompromised patients


C. difficile is a critical infection to identify and treat aggressively (i.e., antibiotics)

Suggested treatment protocol is the responsibility of the ordering clinician; however, treatment

generally includes

Stop ALL non essential antibiotics

Confirm that C. difficile toxin is present via confirmatory method (DRG assay works for this)

AVOID empiric therapy until diagnosis is confirmed

Treat


Campylobacter

Campylobacter enteritis due to C. jejuni, C. coli, and C. lari are clinically indistinguishable

Complaints include belly pain, cramping, and diarrhea

Treatment is generally supportive (except for immunocompromised patients)


Escherichia coli (E. coli) 0:157

While E. coli may be considered normal flora in some humans, significant

pathogenic strains exist

Pathogenic E. coli strains are categorized into pathotypes

Six pathotypes are associated with diarrhea and collectively are referred to as

diarrheagenic E. coli.


Diarrheagenic Escherichia coli types

Shiga toxin-producing E. coli (STEC).

Often times, this is the specific pathotype involved in the more noteworthy outbreaks

The Shiga toxin producing E. coli strains include two major strains: Stx1 and Stx2

Enterotoxigenic E. coli (ETEC)

Suggested treatment protocol is the responsibility of the ordering clinician; however, treatment generally includes

Supportive therapy (hydration)

Antibiotics should be avoided

Antibiotics and Imodium® may increase the risk of hemolytic uremic syndrome (HUS), a potentially fatal

complication

Interpreting the Helicobacter pylori (HP) values on the GPP

The HP values are one of the exceptions to the ≥ 350 rule for many of the

analytes. For these, the cut off values are below:

Helicobacter pylori (H. pylori) ≥ 51.75

cagA ≥ 199.5

vacA ≥ 181.5

iceA ≥ 350.5

oipA ≥ 1500

Interpreting the GPP report

What are the virulence factors (VF) as reported on the GPP?

These factors give additional information to the treating physician regarding the potential for the

development of gastric cancer (GC)

The development of GC involves the interplay among three important factors

The agent (generally, H. pylori) and its pathogenicity

Host (patient) characteristics

Environment

Additional information regarding the individual VF is available on our website for the DRG HP panel

(HPP) report

Interpreting the GPP report The HP stool antigen value is the other analyte that differs from the ≥ 350

rule. The cut off value for the stool antigen is 3 ng/mL

H. pylori stool antigen ¹ : Negative or positive

The ‘superscript one’ refers to the area of the report that reads:

“Please note: The Helicobacter pylori (H. pylori) value can remain positive even in

the absence of an active infection. The H. pylori stool antigen functions to

determine if the infection is active or current; therefore, favoring treatment. The

cut off value for HP stool antigen is 3ng/mL”

Critical numbers in the Bacteria and Toxins by PCR section of GPP Report

Below are key values that should alert the clinician to a significant issue

Clostridium difficile (C. difficile) toxin A and/or toxin B

C. difficile is a potentially noteworthy infection that generally requires antibiotic treatment

If symptoms warrant, ALL non-essential antibiotics should be stopped

Treat case with appropriate antibiotic

H. pylori stool antigen

A positive value indicates an active or current infection, and usually suggests treatment

This is even more critical when the patient is positive for one or more of the virulent factors


Reliable methods to determine eradication of HP infection

Noninvasive testing options for H. pylori include serology, urea breath

testing (UBT), and stool antigen

Serologic testing has poor sensitivity and specificity values

The sensitivities and specificities of UBT and stool antigen are essentially equivalent

However, UBT requires the patient make significant dietary and medical changes


Salmonella spp.

Significant diarrheal illness

Most patients develop diarrhea, fever, and abdominal cramps within 12 and 72 hours after

infection

Usually self-limited, but may be of special concern for immunocompromised patients

Severe illness may require hospitalization for blood borne illness


Shigella spp.

Significant diarrheal illness

Symptoms include diarrhea (sometimes bloody), fever, abdominal pain, and tenesmus

Symptoms usually self limited except in immunocompromised

Bismuth subsalicylate (e.g., Pepto-Bismol®) may be helpful

Antibiotics should be avoided

If any of the bacteria or toxins, or stool antigen are determined positive by

DRG, AND the antibiotic resistance box is checked on the TRF, you will see the

report below


Each of the values listed in the Antibiotic Resistance by PCR section of the

report are commonly used antibiotics for the treatment of H. pylori

However, the antibiotics are not specific for H. pylori

The result will be either sensitive or resistant

Resistant values indicate antibiotics that likely won’t work for this patient

It is important to note that the results in this section are not organism specific;

rather, they are patient specific


Resistance traits are genetically encoded, so at DRG we test for the specific genes

that confer antibiotic resistance (AR)

Although nucleic acid-based detections systems are generally rapid and sensitive,

it is important to remember that the presence of a resistance gene does not

necessarily equate to treatment failure

Resistance is an ever evolving field as bacteria continue to evolve with the

transfer of resistance one to another


Beta lactam antibiotics target the penicillin-binding proteins (PBPs). The

beta-lactam ring portion of this group of antibiotics binds to these different

PBPs, rendering them unable to perform their role in cell wall synthesis

This then leads to death of the bacterial cell due to osmotic instability or

autolysis

Specific examples include penicillin, carbapenam, and cephalosporin


Nitroimidazole antibiotics have been used to combat anaerobic bacterial and

parasitic infections

The most common example is metronidazole (Flagyl®).


Fluoroquinolones belong to a family of broad spectrum, systemic antibacterial

agents

Fluoroquinolones are active against a wide range of aerobic gram-positive and

gram-negative organisms

Examples include ciprofloxacin (Cipro®) and lexofloxacin (Levaquin®).


Tetracycline is generally used in the treatment of infections of the urinary

tract, respiratory tract, and the intestines

The use of tetracycline is becoming more and more limited due to widespread

development of resistance in the causative organisms


Genetic resistance is associated with presence of the nitroimidazole

resistance genes nimA-H and nimJ

The affected drugs include metronidazol, tinidazol, and ornidazol


Vancomycin is indicated for the treatment of serious, life -threatening

infections by gram-positive bacteria unresponsive to other antibiotics



Next, let’s move on to the GI Health Markers section of the GPP report


Anti-Gliadin IgA

This first analyte is to determine if a patient has a sensitivity to gluten

This assay does NOT confirm celiac disease, as that is only possible through an invasive small

intestinal biopsy

The anti-gliadin assay is a superlative non invasive alternative to detect the antibodies

commonly found in patients that have celiac disease

Our assay detects circulating IgA antibodies to gliadin, an antibody found in ~80% of patients

with celiac disease

It is directed against the alpha/beta and gamma (α,β,γ) gliadins, and may also found in a number

of patients who are not enteropathic

Patients with values over 100 U/L should be considered for a gluten free diet to relieve

GI symptoms such as bloating, diarrhea, constipation, and irritable bowel


Calprotectin and Lactoferrin

Elevated levels of calprotectin and lactoferrin indicate that

neutrophils (PMNs) have migrated in to the lumen of the intestine

These PMNs are markers of inflammation within the gut

High calprotectin and lactoferrin levels are indicative of inflammatory bowel disease (IBD); however, the

assay does not differentiate ulcerated colitis from Crohn disease

This test may be useful for monitoring disease activity

The test is also positive in patients with bacterial infection


Fecal fat

Values over 400 are indicative of fat malabsorption syndromes that lead to steatorrhea

Disorders of exocrine pancreatic function

Celiac disease

Short bowel syndrome (in which much of the small intestine has had to be surgically removed and

the remaining portion cannot completely absorb all of the fat)

Small bowel bacterial overgrowth syndrome (SIBO)


Fecal occult blood (FOBT)

This is the only non quantitative assay we perform at DRG Laboratory

This assay looks for microscopic (occult) blood in the stool secondary to upper or

lower intestinal bleeding; however, false positives are possible

The value with be negative or positive

A positive value should prompt a search for the cause of the bleeding


sIgA 1 and sIgA 2

These markers are indicative of secretory IgA

This is the antibody that lines the interior of the intestines

Cut off value → 1000; however much higher values are possible

Anything that comes in to contact with the mucosa of the gut

may be seen as a foreigner by the immune system

sIgA 1 > sIgA 2 → IBD


Next, let’s move to the Parasites by PCR section of the GPP report


Blastocystis hominis

Gastrointestinal parasite found in ~23% of US population (in 2000)

Four commonly described forms are the vacuolar, granular, amoeboid, and cyst forms

Fecal oral transmission within humans has only been identified for the cyst form

Symptoms include diarrhea, nausea, abdominal cramps, bloating, excessive gas, and anal

itching

May also be associated with irritable bowel syndrome (IBS)

Suggested treatment includes nitazoxanide

Entamoeba histolytica

This parasite may infect up to 10% of the world’s population

Symptoms can include fulminating dysentery, bloody diarrhea, weight loss, fatigue,

abdominal pain, and amoeboma

Cysts survive outside the host in water, in soils, and on foods


Giardia spp.

Intestinal parasite of infected humans

Infection occurs by ingesting or coming into contact with contaminated food, soil, or

water (seasonal infection from fresh water lakes is common)

Symptoms include violent diarrhea, excess gas, stomach or abdominal cramps, upset

stomach, and nausea


Trichomonas spp.

Intestinal parasite of infected humans

The trichomonad species include T. vaginalis, T. tenax, T. hominis

T. hominis is also known as Pentatrichomonas hominis

This third organism inhabits the intestinal tract in the area of the cecum (portion of the intestines

between the small and large bowel)

Diagnosis of this organism as ‘pathogenic’ is currently controversial, but is believed to be a marker

for other, clearly pathogenic organisms in the stool

Furthermore, this organism is also believed to be associated with diarrhea, in addition to being

found in some liver abscesses


Please keep in mind that values in the range of 350-900 MFI (particularly among

the parasites) are ‘molecularly positive,’ but may not be clinically significant

Treatment based on these results is recommended only if clinical symptoms and

appropriate assessment of the patient warrant


Lastly, let’s move to the Fungi by PCR section of the report


Candida spp.

This yeast is an opportunistic infection commonly found on skin

Gastrointestinal infection with candida species is usually a symptom of dysbiosis

Return to a healthy gut microbiome is most often suggested

Candida infection also accompanies overzealous use of antibiotics or antacids,

alcohol overuse, or poor diet


The results indicated on this report represent organisms that may be commensal

and normally found in a given patient, particularly given his or her environmental

exposures. A positive value does not necessarily indicate the need of treatment.

Values given here should always be interpreted in concert with the greater

clinical picture for an individual patient. Any laboratory value should never be

taken in isolation without careful clinical judgement.

DRG Laboratory

References

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Yoshikawa H, Wu Z, Kimata I; et al. (January 2004). "Polymerase chain reaction-based genotype classification among human Blastocystis hominis populations isolated from differrentcountries". Parasitol. Res. 92 (1): 22–9.

Blastocystis hominis infection. Diseases and Infections. Mayo Foundation for Medical Education and Research. Last accessed October 7, 2015.

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Interpreting the GI Pathogen Plus Profile (GPP) Report · Interpreting the DRG GPP report Fecal fat Values over 400 are indicative of fat malabsorption syndromes that lead to steatorrhea