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Reference Guide
KBMO Diagnostics
Zonulin Add-On

Zonulin Add-On

KBMO Diagnostics
Zonulin Add-On
KBMO Diagnostics
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Zonulin Add-On
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About the Test

Our New Unique Zonulin Assay is Now Included on the FIT 132 and FIT 176

Developed in collaboration with Dr. Brent Dorval and Dr. Alessio Fasano, KBMO Diagnostics has created a proprietary Zonulin assay, now included as part of the FIT 132 and FIT 176 panels. 

This proprietary Zonulin assay is the only assay currently available that does not cross-react with haptoglobin, properdin, or any complement fragments, ensuring precise and reliable results. 

This achievement is attributed to the creation of a unique recombinant Zonulin protein, meticulously engineered to uphold accuracy and stability. Notably, the assay's measurement of Zonulin antibody levels offers enhanced consistency, circumventing the fluctuations often observed in conventional Zonulin protein assays and providing a reliable indicator of the degree of leaky gut present.

This test is available as a stand-alone test requiring a blood spot sample, and is included in the FIT 132, FIT 176, and Gut Barrier Panels by KBMO Diagnostics.  The FIT 132 and FIT 176 Panels are available as blood spot and serum tests, and the Gut Barrier Panel requires a blood spot sample.   

What is Zonulin?

Zonulin is a protein that plays a pivotal role in regulating intestinal permeability, a critical aspect of gut barrier function. Under normal physiological conditions, zonulin is involved in the maintenance of tight junctions between intestinal epithelial cells, which form a barrier that controls the passage of molecules and substances from the gut lumen into the bloodstream. This function is crucial for preventing the entry of harmful pathogens, toxins, and undigested food particles into systemic circulation, thereby maintaining gut homeostasis and overall health. [3., 4.]

However, in pathological conditions such as leaky gut syndrome, dysregulation of zonulin production and activity can occur, leading to increased intestinal permeability. In leaky gut, the tight junctions between epithelial cells become compromised, allowing the unrestricted passage of substances across the intestinal barrier. This breach in gut integrity can trigger systemic inflammation, immune dysregulation, and contribute to the development or exacerbation of various chronic health conditions, including autoimmune diseases, allergies, and gastrointestinal disorders. [3., 4.]

What is the Clinical Relevance of Blood Testing for Zonulin?  

Leaky gut may be a progressive condition, meaning that its severity can worsen over time if left unaddressed.  [11.]  Zonulin antibody testing emerges as a valuable tool for assessing the degree of intestinal permeability and monitoring the progression of leaky gut in a more reliable manner than blood testing for the zonulin protein, which can show variability from sample to sample.  [16.]

By measuring levels of zonulin antibodies in the bloodstream, clinicians can gain insights into the activity of zonulin and the integrity of the gut barrier. This information enables healthcare providers to tailor interventions and therapies aimed at restoring gut health and mitigating the systemic consequences of leaky gut. 

What is the Clinical Significance of IgA 1 + 2 Antibody Testing?

IgA 1 and IgA 2 testing in food sensitivity tests holds clinical significance primarily in the context of assessing mucosal immunity and gut barrier function, and it may play a role in the development of immune tolerance.  [6., 9.]  

Immunoglobulin A (IgA) is the primary antibody found in mucosal secretions, including those of the gastrointestinal tract. IgA defends against pathogens and antigens present in the gut, as well as in maintaining the integrity of the gut epithelium and developing immune tolerance to beneficial gut microbes.  [6.]

Dysregulation of mucosal immunity, characterized by alterations in IgA production, has been implicated in various gastrointestinal disorders, including inflammatory bowel diseases, celiac disease, and irritable bowel syndrome. [15.]

By measuring IgA 1 and IgA 2 levels in the context of food sensitivity testing, healthcare providers can gain insights into the status of mucosal immunity, the integrity of the gut barrier, and immune activity in the GI tract. 

Abnormalities in IgA levels may indicate disruptions in gut barrier function, increased intestinal permeability (leaky gut), or heightened immune responses to dietary antigens, all of which can contribute to gastrointestinal symptoms and systemic inflammation.

What is the Clinical Significance of IgG 1-4 Antibody Testing?

The Zonulin Assay by KBMO Diagnostics employs testing for all four IgG antibody subclasses: IgG 1-4.  IgG antibodies 1-3 activate a branch of the innate immune system called complement, which stimulates an inflammatory response.  In contrast, IgG 4 does not have this capability.  

Some studies indicate that IgG-mediated immune responses might contribute to the pathogenesis of gastrointestinal inflammation and leaky gut.  Additionally, testing antibody levels against zonulin may be more reliable than testing for zonulin itself in the blood due to stability factors.  [5., 14., 16.]   

IgG4, a subtype of immunoglobulin G antibodies, plays a crucial role in modulating immune responses.   

It's essential to maintain a balanced level of IgG4, as excessive amounts can paradoxically lead to increased inflammation and immune sensitization.  Increased IgG4 levels have been associated with allergies and with autoimmune conditions.  For instance, elevated IgG4 levels have been implicated in conditions such as rheumatoid arthritis, myasthenia gravis, pemphigus vulgaris and thrombotic thrombocytopenic purpura. [8., 10., 13.]

What is the Clinical Significance of C3d Testing? 

C3d (Complement Component 3) is a protein of the innate immune system that can promote an inflammatory response.  The inclusion of complement proteins C3d in the Zonulin Assay by KBMO Diagnostics provides a more comprehensive assessment of the immune response to dietary antigens. 

Complement proteins play a crucial role in the immune cascade triggered by IgG-mediated reactions. Specifically, C3d is involved in the opsonization of immune complexes, facilitating their recognition and clearance by phagocytic cells; their role can increase the actions of IgG antibodies many times over. By measuring levels of C3d alongside IgG antibodies against common foods, this test offers valuable insights into the inflammatory response associated with food sensitivities.

Complement activation, particularly through the C3d pathway, may contribute to the pathogenesis of various immune-mediated disorders, including food sensitivities and allergic reactions.  [17.]

Who Can Benefit from the Zonulin Assay by KBMO Diagnostics?

Individuals Seeking to Optimize Health: even in the absence of symptoms, KBMO’s Zonulin Assay can offer insights into gut health, providing an opportunity for preventative measures against potential health issues and supporting the body’s natural processes.

Patients with Chronic Digestive Dysfunction: for those who have suffered from chronic symptoms with or without a clear diagnosis, the Zonulin Assay from KBMO Diagnostics can help identify underlying food sensitivities or inflammation in the gut that may be contributing to their health issues.

Autoimmune Diseases: since gut health is closely linked to the immune system, identifying and addressing compromised gut barrier health can provide additional treatment options and provide crucial support in managing autoimmune conditions. [1.]

Gastrointestinal Disorders: for patients struggling with Small Intestinal Bowel Overgrowth (SIBO), Irritable Bowel Syndrome (IBS) and Inflammatory Bowel Disease (IBD), the Zonulin Assay by KBMO Diagnostics can identify previously silent leaky gut that may be contributing to symptoms like gas, bloating, diarrhea, and constipation. [2., 12.]

Digestive Complaints: people experiencing unexplained digestive issues such as gas, bloating, heartburn, indigestion, diarrhea, or constipation can identify potential causes like leaky gut and receive targeted treatment recommendations.  [12.] 

Neurological and Cognitive Issues: the vagus nerve is the primary nerve that innervates the digestive tract, and is considered the “highway of the gut-brain axis”.  Insights into the gut-brain axis through the Zonulin Assay may reveal how leaky gut impacts an individual’s cognitive function and affects memory, concentration, and brain fog. [3., 4.]

Skin Conditions: conditions like acne and psoriasis have been linked to gut health. Identifying and addressing leaky gut can be a part of a comprehensive treatment plan to improve and restore skin health. [7.]

Mood Disorders: the gut-brain connection means that digestive inflammation can impact mood and emotional well-being, making the Zonulin Assay by KBMO Diagnostics a valuable assessment tool for individuals with these conditions. [3., 4.]


[1.] Brady DM. Molecular Mimicry, the Hygiene Hypothesis, Stealth Infections and Other Examples of Disconnect between Medical Research and the Practice of Clinical Medicine in Autoimmune Disease. Open Journal of Rheumatology and Autoimmune Diseases. 2013;03(01):33-39. doi: 

[2.] Capobianco I, Di Vincenzo F, Puca P, Becherucci G, Mentella MC, Petito V, Scaldaferri F. Adverse Food Reactions in Inflammatory Bowel Disease: State of the Art and Future Perspectives. Nutrients. 2024 Jan 25;16(3):351. doi: 10.3390/nu16030351. PMID: 38337636; PMCID: PMC10857040. 

[3.] Fasano A. Zonulin and Its Regulation of Intestinal Barrier Function: The Biological Door to Inflammation, Autoimmunity, and Cancer. Physiological Reviews. 2011;91(1):151-175. doi:

[4.] Fasano A. All disease begins in the (leaky) gut: role of zonulin-mediated gut permeability in the pathogenesis of some chronic inflammatory diseases. F1000Res. 2020 Jan 31;9:F1000 Faculty Rev-69. doi: 10.12688/f1000research.20510.1. PMID: 32051759; PMCID: PMC6996528. 

[5.] Gocki J, Bartuzi Z. Role of immunoglobulin G antibodies in diagnosis of food allergy. Postepy Dermatol Alergol. 2016 Aug;33(4):253-6. doi: 10.5114/ada.2016.61600. Epub 2016 Aug 16. PMID: 27605894; PMCID: PMC5004213.

[6.] Gutzeit C, Magri G, Cerutti A. Intestinal IgA production and its role in host-microbe interaction. Immunol Rev. 2014 Jul;260(1):76-85. doi: 10.1111/imr.12189. PMID: 24942683; PMCID: PMC4174397.

[7.] Katta R, Schlichte M. Diet and dermatitis: food triggers. J Clin Aesthet Dermatol. 2014 Mar;7(3):30-6. PMID: 24688624; PMCID: PMC3970830. 

[8.] Koneczny I. Update on IgG4-mediated autoimmune diseases: New insights and new family members. Autoimmunity Reviews. 2020;19(10):102646. doi:

[9.] Konstantinou GN, Nowak-Węgrzyn A, Bencharitiwong R, Bardina L, Sicherer SH, Sampson HA. Egg-white-specific IgA and IgA2 antibodies in egg-allergic children: is there a role in tolerance induction? Pediatr Allergy Immunol. 2014 Feb;25(1):64-70. doi: 10.1111/pai.12143. Epub 2013 Oct 7. PMID: 24118158; PMCID: PMC4134474.

[10.] Maslinska M, Dmowska-Chalaba J, Jakubaszek M. The Role of IgG4 in Autoimmunity and Rheumatic Diseases. Front Immunol. 2022 Jan 25;12:787422. doi: 10.3389/fimmu.2021.787422. PMID: 35145508; PMCID: PMC8821096. 

[11.] Paray BA, Albeshr MF, Jan AT, Rather IA. Leaky Gut and Autoimmunity: An Intricate Balance in Individuals Health and the Diseased State. Int J Mol Sci. 2020 Dec 21;21(24):9770. doi: 10.3390/ijms21249770. PMID: 33371435; PMCID: PMC7767453.

[12.] Pasta A, Formisano E, Calabrese F, Plaz Torres MC, Bodini G, Marabotto E, Pisciotta L, Giannini EG, Furnari M. Food Intolerances, Food Allergies and IBS: Lights and Shadows. Nutrients. 2024 Jan 16;16(2):265. doi: 10.3390/nu16020265. PMID: 38257158; PMCID: PMC10821155. 

[13.] Qin L, Tang LF, Cheng L, Wang HY. The clinical significance of allergen-specific IgG4 in allergic diseases. Front Immunol. 2022 Oct 25;13:1032909. doi: 10.3389/fimmu.2022.1032909. PMID: 36389804; PMCID: PMC9648126. 

[14.] Simeonova D, Ivanovska M, Murdjeva M, Carvalho AF, Maes M. Recognizing the Leaky Gut as a Trans-diagnostic Target for Neuroimmune Disorders Using Clinical Chemistry and Molecular Immunology Assays. Curr Top Med Chem. 2018;18(19):1641-1655. doi: 10.2174/1568026618666181115100610. PMID: 30430944.

[15.] Song DJ, Shen J, Chen MH, et al. Association of Serum Immunoglobulins Levels With Specific Disease Phenotypes of Crohn’s Disease: A Multicenter Analysis in China. Frontiers in Medicine. 2021;8. doi:

[16.] Vojdani A, Vojdani E, Kharrazian D. Fluctuation of zonulin levels in blood vs stability of antibodies. World J Gastroenterol. 2017 Aug 21;23(31):5669-5679. doi: 10.3748/wjg.v23.i31.5669. PMID: 28883692; PMCID: PMC5569281.

[17.] Yves Laumonnier, Rabia Ülkü Korkmaz, Nowacka AA, Jörg Köhl. Complement‐mediated immune mechanisms in allergy. European Journal of Immunology. 2023;53(10). doi:

Vojdani A, Vojdani E, Kharrazian D. Fluctuation of zonulin levels in blood vs stability of antibodies. World J Gastroenterol. 2017 Aug 21;23(31):5669-5679. doi: 10.3748/wjg.v23.i31.5669. PMID: 28883692; PMCID: PMC5569281.

About the Test

This is a single-marker add-on test measuring zonulin. It can be added to the FIT 44 or FIT 22.

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Lab Test Information
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Lab Company
KBMO Diagnostics
Sample Type
Blood Spot
Shipping Time
3 - 7 days
Turnaround Time
10 days
Test Preparation Starts
No test preparation required
Number of Collection Days
1 day
Methods Used For Processing
Lab Certifications
CLIA Certified
CAP Accredited
ISO 15189
COLA Accredited
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