A Guide to Vitamin D and IBD Testing

About the IDK® Vitamin D and IBD Testing Panel

IBD and vitamin D deficiency are both highly prevalent health issues, particularly in the US but also around the world. Studies have connected the two, showing that vitamin D deficiencies can lead to an increased risk of developing IBD. It has also been found that many individuals with IBD have a higher prevalence of vitamin D deficiency. It is suspected that the gut microbiome is responsible for metabolizing vitamin D from its precursor form into its active form, thus, a more diverse gut microbiome will allow for increased metabolism, and subsequently, more active vitamin D.

This connection between IBD and vitamin D suggests any lab that runs testing for IBD should consider adding vitamin D tests to their portfolio, in order to better evaluate the overall health of individuals affected by IBD. Immundiagnostik, Inc. has solutions for both IBD and vitamin D testing to create the IDK® IBD + Vitamin D Testing Panel.

Download the IDK® Vitamin D and IBD Testing Panel Guide to discover more.


Calprotectin shows high stability in feces and has been established as a fecal marker of inflammatory bowel diseases (IBD) because it is released into the stool by the intestinal mucosa in response to intestinal inflammation. It allows a reliable differentiation between organic intestinal diseases (IBD, colon cancer) and functional intestinal diseases (irritable bowel syndrome).

A calprotectin protein - calprotectin is a biomarker of inflammatory bowel disease.

Pancreatic Elastase

Pancreatic elastase is a proteolytic enzyme produced in the pancreatic acinar cells and then secreted into the duodenum where it is converted into an active enzyme. Upon activation, pancreatic elastase degrades proteins and plays an important role in digestion.

The stool concentration of pancreatic elastase reflects the secretory capacity of the pancreas, allowing for the diagnosis of exocrine pancreatic insufficiency (EPI). EPI is characterized by reduced pancreatic enzyme activity which inhibits digestion.


Zonulin is a tight-junction regulating protein in the digestive tract. Zonulin binds to a specific receptor on the surface of intestinal epithelia and triggers a cascade of biochemical events which induces tight junction disassembly and a subsequent permeability increase of the intestinal epithelia, allowing some substances to pass through and activate immune reactions.

An illustration comparing the normal tight junctions of healthy villi versus leaky gut progression.

An increased intestinal permeability, also known as ‘leaky gut, is associated with metabolic syndrome, obesity, and several autoimmune, inflammatory, and neoplastic diseases. Based on the evidence, leaky gut plays a meaningful role in diseases such as multiple sclerosis, rheumatoid arthritis, asthma, and inflammatory bowel diseases.

Secretory IgA

Fecal secretory IgA (sIgA) is the most abundant class of antibodies found in the intestinal lumen. The immune tolerance of the intestinal mucosa can be evaluated using the concentration of fecal sIgA. A deficiency of sIgA points to diminished activity of the mucosa immune system, whereas increased sIgA values indicate increased activity and local inflammation of the intestinal mucosa.


α1-Antitrypsin is released during inflammatory processes by polymorphonuclear neutrophilic granulocytes (PMN) to reduce the proteolytic activity of PMN elastase in the inflammation region. α1-Antitrypsin is also a serine proteinase inhibitor, thus it acts as both a regulatory and anti-inflammatory protein.

The measurement of fecal α1-Antitrypsin concentration is used to evaluate and monitor chronic inflammatory intestinal diseases because it is a marker for intestinal protein loss and permeability as well as intestinal inflammation.


Lysozyme is an antimicrobial enzyme that is part of the immune system and is detected in all cells of the inflammatory infiltrate during an acute flare of Crohn’s disease. To some extent, lysozyme is also secreted actively by mononuclear cells into the bowel lumen.

An illustration of the human intestines showing where Crohn's disease affects these organs.



Myeloperoxidase (MPO) is a hemoprotein that is secreted by neutrophils upon their activation. The determination of MPO in stool, therefore, reflects the inflammatory activity of Crohn’s disease or ulcerative colitis.

25-OH Vitamin D3/D2

Inactive vitamin D is hydroxylated in the liver to form 25-OH vitamin D, which is the major storage form of vitamin D. The 25-OH Vitamin D3/D2 LC-MS/MS Kit is intended for the quantitative determination of 25 OH vitamin D3 and 25 OH vitamin D2 in serum and plasma, which can give an accurate evaluation of the overall vitamin D supply in the body and reveal if there is a vitamin D deficiency.

1,25 (OH)2 Vitamin D

25-OH vitamin D is metabolized in the liver into 1,25 (OH)2 vitamin D. A deficiency of 1,25 (OH)2 vitamin D can be explained by metabolic disturbances, caused either by genetic enzyme defects (rare) or kidney malfunctions (more common). Even slightly impaired kidney function can lead to a decrease of 1,25 (OH)2 vitamin D concentration.

An illustration of how vitamin d is absorbed by the body through sunlight or food consumption, and then how it is synthesized within the body and organs.

Since 1,25 (OH)2 vitamin D has important functions in calcium metabolism as well as supplementing secretion of parathyroid hormone from the parathyroid glands, increasing kidney malfunctioning leads to the development of renal osteopathy, which is characterized by osteomalacia and osteitis fibrosa.

Vitamin D Combi Immutube®

The main storage form and the best measure of vitamin D supply is 25-OH vitamin D3, which is metabolized by the enzyme, 1α-hydroxylase, into the hormone 1,25 (OH)2 vitamin D3/D2 (D hormone) in the kidney. Since D hormone concentrations change in response to the demands of metabolism, the concentration will indicate the kidney’s functioning abilities.

If 25-OH vitamin D3 is metabolized by the enzyme, 25-OH vitamin D3 – 24-hydroxylase, then 24,25 (OH)2 vitamin D3 is formed. This form of vitamin D is thought to be related to bone metabolism and chronic kidney disease.

The IDK® Vitamin D Combi ImmuTube LC-MS/MS Kit extracts five vitamin D metabolites in a specific single-step affinity purification, thereby separating it from disturbing matrix components and isobaric interferences and allowing for the detection of the five metabolites with high specificity and sensitivity.

1,25 OH Vitamin D Slurry

The IDK® 1,25 OH Vitamin D Slurry is used in conjunction with the LC-MS/MS testing method for vitamin D. After the sample extraction process, the slurry is briefly added to the serum for a short period of incubation in order to prepare it for the LC-MS/MS testing device.

Add Vitamin D to Your IBD Testing Panel

Several studies have demonstrated a clear connection between vitamin D deficiency and the presence of IBD. Vitamin D deficiencies can lead to an increased risk of developing IBD, and many individuals with IBD also have a higher prevalence of vitamin D deficiency. These findings indicate the gut microbiome may be involved in metabolizing vitamin D into its active form such that a more diverse gut microbiome is related to an increased rate of metabolism.

Immundiagnostik, Inc. offers a full Vitamin D and IBD panel of immunoassays which allow labs to help better evaluate the overall health of individuals affected by IBD. This panel combines our most popular gastrointestinal ELISAs, which help identify intestinal inflammation and permeability, with our vitamin D kits to help analyze active and precursor vitamin D supply.

Contact us to learn more about adding vitamin D to your lab’s IBD testing panel.

No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.

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