Targeted faecal biomarkers in patients with Rome III-confirmed IBS
| Biomarker | Assay used | Definition of abnormal result | Interpretation of abnormal result in context of IBS |
|---|---|---|---|
| Culture for pathogenic or potentially pathogenic bacteria* | Routine culture. | Present. | Suggestive of GI pathogenic disease. |
| Culture for beneficial bacteria (Lactobacillus, Bifidobacterium) | Routine culture. | Growth in 1 or fewer quadrants (Lacto)/2 or fewer quadrants (Bifido). | Reduced numbers of beneficial symbionts (dysbiosis).13 14 |
| Pancreatic elastase-1 | Monoclonal antibody EIA (Pancreatic elastase 1 stool test, ScheBo Biotech USA, Colorado Springs, Colorado, USA). | <200 μg/g | Suggestive of exocrine pancreatic insufficiency. |
| Calprotectin | ELISA, PhiCal, Lysaker, Norway. | >50 μg/g | Suggestive of neutrophilic inflammation, for example, IBD. |
| Eosinophil protein X | Modified EDN sandwich ELISA†, MBL International, Woburn, Massachusetts, USA. | >7 μg/g | Suggestive of food allergy or parasites (or other causes of eosinophilic inflammation). |
| Parasites‡ | EIA for Entamoeba histolytica/dispar, Giardia lamblia, Cryptosporidium; light microscopy for all other parasites. | E. histolytica/dispar, G. lamblia, Cryptosporidium: EIA-positive§, Blastocystis hominis: present on microscopic exam, all other parasites: present on microscopic exam. | |
| Occult blood | Hemosure one-step iFOB test, (Hemosure Irwindale, California, USA). | Present. | Suggestive of inflammation, malignancy, enteric infection. |
Seven biomarkers were chosen for determination of prevalence of abnormal results in a Rome III-confirmed IBS population. All of these have been reported as evidence of potential aetiological roles in production of IBS symptoms.
*See online supplementary table 1 for bacterial/fungal pathogen designations.
†Laboratory-derived test (LDT) based on.10
‡See online supplementary table 2 for parasite pathogen designations.
§Detection by ELISA (EIA).
EDN, eosinophil-derived neurotoxin; IBD, inflammatory bowel disease; IBS, irritable bowel syndrome; iFOB, immunochemical faecal occult blood; MBL, Medical and Biological Laboratories Co, Ltd.