The value of broad access to gut health tests in primary care

Abdominal pain, diarrhea, nausea, vomiting, bloating, weight loss, dyspepsia, oily stool production, iron deficiency, or unexplained malabsorptive symptoms. Those common complaints in a primary care practice may reflect self-limited illness like acute gastroenteritis, food-borne illness, or indigestion. However, they may also signal more serious autoimmune, cancerous, cardiometabolic, infectious, genetic, and inflammatory conditions with meaningful downstream consequences for patients.

In this article:

Clinical challenge | Why it matters | Ordering recommendations | Interpreting test results | Next steps | Supporting resources

Clinical challenge: Complexity in navigating gut health diagnoses

Because gut health symptoms frequently overlap in gastrointestinal (GI) conditions—celiac disease, exocrine pancreatic insufficiency (EPI), Helicobacter pylori (H pylori) infection, infectious diarrhea, and inflammatory bowel disease (IBD)—clinical presentation alone is often insufficient for a definitive diagnosis. (see Fig A) The challenge for clinicians is to accurately and promptly differentiate between potential causes to initiate proper management and avoid the detrimental health consequences  of a delayed gastrointestinal diagnosis. (see Fig B)

A practical, yet comprehensive, diagnostic approach can clarify etiology, reduce diagnostic delay, and support earlier clinical decisions, whether by primary care physicians or gastroenterologists. 

A differential diagnostic approach in this situation is key to ensuring timely and precise clinical management that helps avoid the significant health consequences of a delayed or missed diagnosis.

Why it matters: The whole-body gut health connection

Interconnected across a variety of conditions, gut health is a cornerstone of whole-body wellness. Unfortunately, digestive diseases remain a substantial health burden in the United States. IBD alone affects an estimated 3.1 million people.⁴

Timely, first-line laboratory testing can help primary care physicians transform patient care on a large scale by screening for common pathologies, narrowing the differential diagnosis earlier, selecting the right next step, and coordinating gastroenterology specialty care more efficiently when needed. 

Ordering recommendations: Leverage Quest’s broad gut health testing portfolio

To support the gastroenterology care continuum, Quest Diagnostics offers a spectrum of gut health screening and diagnostic tests that align with the latest clinical guidelines. Primary care providers can help patients stay ahead of serious complications by ordering key tests at the first sign of gut distress.

Recommended tests: Celiac disease

Celiac disease requires both diagnostic testing to determine the condition as well as ongoing testing to monitor progress and to detect associated conditions.

Celiac Disease Comprehensive Panel with Gliadin Antibody (IgG)

• Test code: 36336
• CPT^® codes: 86364, 82784

Components include Tissue Transglutaminase (tTG) Antibody (IgA) [8821], IgA (Immunoglobulin A) [539].

Tissue Transglutaminase (tTG) Antibody (IgA)

• Test code: 8821
• CPT code: 86364 

Recommended test: EPI

Quest’s noninvasive and highly specific test enables providers to diagnose EPI, an underrecognized but clinically significant gastrointestinal condition.

Pancreatic Elastase-1

• Test code: 14693
• CPT code: 82653

Recommended tests: H pylori infections

Quest offers a full H pylori infection testing menu aligned with American College of Gastroenterology (ACG) guidelines.⁸

The H pylori Urea Breath Test is indicated for diagnosing active infection in individuals older than 3 years to those under 60 years with no alarming symptoms and for confirming eradication of infection 4 weeks post-treatment. The H pylori Stool Antigen Test is indicated for the same use cases but can also be used for children under the age of 3.

Helicobacter pylori, Urea Breath Test

• Test code: 14839
• CPT code: 83013*

Helicobacter pylori Antigen, EIA, Stool

• Test code: 34838
• CPT code: 87338*

Recommended test: Infectious diarrhea

From a single specimen, Quest’s qualitative PCR panel can simultaneously detect 9 of the most common pathogens associated with infectious diarrhea.

Gastrointestinal Pathogen Panel, Real-Time PCR

• Test code: 38470
• CPT code: 87506*

Includes Campylobacter group, Salmonella species, Shigella species, Vibrio group, Yersinia enterocolitica, Shiga toxin 1, Shiga toxin 2, Norovirus GI/GII, and Rotavirus A.

Recommended test: Inflammatory bowel disease

Using the results of a CBC (6399) and one inflammatory marker—Calprotectin, Stool (test code: 16796), Lactoferrin, Qualitative, Stool (test code: 10156), Lactoferrin, Quantitative, Stool (test code: 17321)—primary care clinicians can utilize Quest’s IBD Differentiation Panel to gain early diagnostic insight. This allows for a more informed, high-priority referral to a gastroenterologist while the patient awaits a definitive endoscopy. The panel also aids gastroenterologists in differentiating between Crohn disease and ulcerative colitis when endoscopic findings are inconclusive.

Inflammatory Bowel Disease Differentiation Panel

• Test code: 16503
• CPT codes: 86021 (x2), 86036, 86671 (x2)

Components include ANCA Screen with Reflex to ANCA Titer [70171], Myeloperoxidase Antibody (MPO) [8796], Proteinase-3 Antibody [34151], Saccharomyces cerevisiae Antibodies (ASCA) (IgG) [10294], Saccharomyces cerevisiae Antibodies (ASCA) (IgA) [10295].

* CPT code is subject to a Medicare Limited Coverage Policy and may require a signed ABN when ordering. 

The CPT^® codes provided are based on American Medical Association guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payer being billed.

Components of panels can be ordered separately.

Interpreting results of gut health tests

Test result interpretation is highly dependent on the condition and the individual test.

Celiac disease test results

If tTG IgA is detected (≥15.0 U/mL), a positive endomysial antibody (IgA) screen further increases the specificity of the diagnosis. If immunoglobulin A is flagged as low based on the age-appropriate reference range, then tTG IgG and/or gliadin (deamidated) antibody (IgG) should be performed for those with a suspected IgA deficiency. According to best practice guidelines, celiac disease should be confirmed with biopsy of the small intestine.

EPI test results

According to American Gastroenterological Association (AGA) guidance, test result levels <100 μg/g stool are consistent with EPI in the appropriate clinical context, and levels of 100 to 200 μg/g stool are considered indeterminate for EPI.⁹

H pylori infection test results

Positive results indicate H pylori infection. Clinical guidelines indicate that all patients with positive H pylori results be offered eradication therapy, as well as post-treatment testing to confirm eradication.⁸

Infectious diarrhea test results

A positive result shows the presence of the pathogens or toxins associated with infectious diarrhea. However, a negative result does not rule out an infection caused by pathogens not included in the panel.

Inflammatory bowel disease test results

Patients with IBD symptoms should undergo testing to rule out other conditions with similar symptoms. Once differential diagnosis is complete and IBD remains the most likely cause, endoscopy and histology should be used to unequivocally diagnose IBD.

Next steps: Coordinating follow-up, treatment, and referral

When initial workups are completed and a gastrointestinal condition is confirmed or strongly suspected, primary care providers can refer patients to a gastroenterology specialist for any follow-up tests, appropriate treatment, and ongoing monitoring. Testing performed up to this point will help the specialist streamline next steps for the patient.

Supporting resources