Inflammatory Bowel Disease (IBD) is a chronic, autoimmune disease, encapsulating both Crohn’s Disease (CD) and Ulcerative Colitis (UC) in which the gastrointestinal tract is affected by inflammation. While the peak incidence rates occur between the ages of 15 to 35, persons of any age and gender are affected with over 40,000 people in Ireland living with IBD. Current disease markers for IBD include blood tests to measure C-reactive protein (CRP), stool tests to measure Faecal Calprotectin (FCP)- both of which indicate inflammation when the levels rise-, endoscopic assessment including histological assessment from tissue biopsies, and intestinal ultrasound to measure bowel wall thickening in correlation to disease activity.  While these markers are well-established and exhibit accuracy, they can vary vastly from patient to patient, thus it is crucial to establish a baseline for comparison of disease activity. Additionally, endoscopic assessment is moderately invasive and there are issues with compliance regarding FCP samples for analysis. Being able to identify which patients are more likely to flare more often and more severely from their time of diagnosis can help to determine how much follow-up each patient will require. 

Previous studies have shown that Body Mass Index (BMI) is inconsistent when used to monitor disease activity in IBD and air displacement plethysmography measurements has displayed ample correlation to recurrence of disease and severity of disease. Higher ratios of visceral adipose tissue to subcutaneous adipose tissue (VAT:SAT) have shown to correspond to a shorter time between IBD flares and increase in disease activity.

The BOD POD is an apparatus used to measure body composition through air displacement plethysmography (ADP) by use of body weight and volume ratios. An oscillating diaphragm between the test and reference chambers produces sinusoidal perturbations that in turn produce small pressure changes. These pressure changes are monitored and analysed for pressure at the frequency of oscillation which is 3 Hz. The BOD POD became the first commercially available air-displacement plethysmograph in the mid-1990s and consists of a BOD POD plethysmography, electronic weighting scale, calibration weights and cylinder, computer, software, and test and reference chambers.

Air displacement plethysmography (ADP) is proving to be an advantageous method of measuring body composition and the relationship between body size and adiposity in clinical practice over other methods such as hydrostatic weighing (HW), duel-energy X-ray absorptiometry (DXA), and multi-compartment [3-compartment (3C) and 4-compartment (4C)] models.

The BOD POD apparatus itself is accurate, safe, and fast, with measurements taking no more than five minutes, and has low running and maintenance costs. It is ideal for those that are elderly, disabled, and those weighing up to 250 kg, with a smaller version, the PEA POD, available for infants and young children. While other methods of body composition measurement have worked well, the BOD POD is non-invasive while measuring weight, body volume, fat and fat-free mass, and lung volumes, and is easy to use for both the healthcare professional and the patient in question.

This study will be a prospective study with visits spanning one year. Each visit will include measurements of height, weight, body composition via BOD POD, FCP, CRP, questionnaires about disease activity and quality of life, as well as endoscopy, intestinal ultrasound, and radiology results, if available per standard of care. An additional visit will be conducted in case of a flare outside the timeframes of the regular visits and the same measurements will be collected. 

Disease activity will be compared against visceral adipose tissue (VAT) as measured through the BOD POD and validated against radiology measurements of VAT if available. Any patient with a diagnosis of Inflammatory Bowel Disease who has flared within 30 days of the baseline will be eligible to participate in the study, allowing that they are willing and able to sign the consent and willing to have their body composition measurement with the BOD POD.

This is a pilot study with an aim of recruiting 30 patients and 15 healthy controls over a period of 12 months with 6 months of prospective follow-up and 24 months of retrospective analysis. After initial analysis, a more specific sample size can be calculated for validation.

Additionally, blood samples will be taken for cytokine analysis and RNA isolation to look at inflammatory markers in those with IBD as compared to healthy controls as well as differences in flaring and non-flaring timepoints per patient.

Healthy controls will participate in the demographics collection, blood sample analysis, and body composition analysis, as well as anything else per standard of care.