Case Study  


Celiac disease manifesting under the guise of IBS: don’t be fooled  

Saskia, a 23-year-old female university student, had suffered with occasional diarrhea for several years by the time she requested a telephone consultation with her GP in August 2020. Over time, Saskia had learnt to live with the problem, and had ‘diagnosed’ herself with irritable bowel syndrome (IBS).

Organic diseases such as coeliac disease should be ruled out before a diagnosis of IBS is made.1 Do not let confirmation bias affect your clinical decision-making.

Celiac disease has a prevalence of 1 percent in the general population,3 but only 10-50 percent of these cases are diagnosed.

August 2020: GP telephone consultation

Saskia explained to the GP that she had been living with IBS for several years, which she had been self-managing with over-the-counter medications. However, over the past 2 months her symptoms had worsened, with: 

  • Watery diarrhea
  • Urgency after eating (opened bowels up to three times per day)
  • Abdominal discomfort/pain  



The GP ascertained that Saskia had not recently travelled internationally and had no family history of gastrointestinal or gynecological disorders. Her weight was stable, and she was currently eating a range of foods with no restrictions on gluten or dairy intake. She had no blood in her stools and was not opening her bowels overnight.

Saskia was in a stable relationship, used the combined oral contraceptive pill, and denied any stress associated with her home life or studies.

The GP noticed that there was no mention of IBS on Saskia’s medical records. On further questioning, Saskia explained that she had ‘self-diagnosed’ after speaking to a friend who had a diagnosis of IBS and researching the syndrome on online forums.

A face-to-face consultation was arranged for a more thorough assessment the same day, given that Saskia had never received a formal diagnosis.

The symptoms of different gastrointestinal conditions are very similar,5 making it difficult and frustrating for both patients and healthcare professionals to identify the relevant condition.





Face-to-face consultation

After testing negative for COVID-19, Saskia attended the appointment. Her GP conducted a thorough abdominal examination, which was unremarkable with no palpable masses; there were also no signs of anemia or jaundice.


Saskia declined the offer of a rectal examination, and as she was young and had no tenesmus or rectal bleeding, the GP felt that it was acceptable to proceed without one. Appropriate safety-netting advice was given in the event her symptoms should progress or change.

The GP sent off the following blood tests:

  • Full blood count (FBC)
  • Inflammatory markers
  • Tissue transglutaminase (tTG) IgA
  • Total IgA

A fecal calprotectin test was considered, but the GP decided it was best to wait for the blood results before deciding how to proceed. 

tTG IgA is the recommended first-line test for celiac disease, together with total IgA to check for IgA deficiency.6




2-week follow-up telephone appointment: blood results

Saskia was phoned by her GP 2 weeks later, after the following blood test results had returned:

  • FBC: normal
  • Inflammatory markers: normal
  • tTG IgA: 131 U/mL (13x ULN)
  • Total IgA: normal (1.9 g/L) 

The GP explained to Saskia that her symptoms were likely due to celiac disease and advised her to begin a strict gluten-free diet.  


The prevalence of celiac disease in patients who are diagnosed with IBS based on symptom criteria is up to 4.7 percent.

28 percent of patients with celiac disease first receive treatment for IBS.8

Screening for celiac disease in patients with IBS, as recommended by international guidelines,9 can help resolve symptoms,10 can improve quality of life, and is cost-effective.11,12




Management and patient support plan

Saskia was referred to a dietitian for specific advice regarding food-labeling, alternatives to gluten-containing foods, and how best to maintain appropriate calcium and iron intake. 


A 3-monthly review was arranged to monitor her tTG IgA until levels returned to normal. In addition, an annual review was set up to check:

  • Her adherence to a gluten-free diet
  • Her FBC
  • For associated symptoms
  • For presence of other autoimmune conditions

Saskia was signposted to celiac disease charities for further information and support, should she require it. 

It is common practice for tTG IgA to be tested every 3 months, until normalized, and once a year as an indicator of diet adherence.6

Other autoimmune conditions are more common in patients with celiac disease than in the general population.3




Do you test tTG IgA every 3 months until normalized, for your patients with celiac disease? 

Yes No


This is a fictional case study, and the image used is of a model.
FBC: full blood count; IgA: immunoglobulin A; tTG: tissue transglutaminase; ULN: upper limit of normal

1. Moayyedi P, Mearin F et al. Irritable bowel syndrome diagnosis and management: a simplified algorithm for clinical practice. United European Gastroenterol J 2017;5(6):773-788

2. Elston D M. Confirmation bias in medical decision-making. J Am Acad Dermatol 2020;82(3):572

3. Gujral N, Freeman H J, Thomson A B. Celiac disease: prevalence, diagnosis, pathogenesis and treatment. World J Gastroenterol 2012;18(42):6036-6059

4. West J, Fleming K M et al. Incidence and prevalence of celiac disease and dermatitis herpetiformis in the UK over two decades: population-based study. Am J Gastroenterol 2014;109(5):757-768

5. Frissora C L, Koch K L. Symptom overlap and comorbidity of irritable bowel syndrome with other conditions. Curr Gastroenterol Rep 2005;7(4):264-271

6. Al-Toma A, Volta U et al. European Society for the Study of Coeliac Disease (ESsCD) guideline for coeliac disease and other gluten-related disorders. United European Gastroenterol J 2019;7(5):583-613

7. El-Salhy M, Hatlebakk J G et al. The relation between celiac disease, nonceliac gluten sensitivity and irritable bowel syndrome. Nutr J 2015;14:92

8. Card T R, Siffledeen J et al. An excess of prior irritable bowel syndrome diagnoses or treatments in celiac disease: evidence of diagnostic delay. Scand J Gastroenterol 2013;48(7):801-807

9. World Gastroenterology Organisation. Irritable bowel syndrome: a global perspective. Available at: Accessed June 2022

10. Ford A C, Chey W D et al. Yield of diagnostic tests for celiac disease in individuals with symptoms suggestive of irritable bowel syndrome: systematic review and meta-analysis. Arch Intern Med 2009;169(7):651-658

11. Mohseninejad L, Feenstra T et al. Targeted screening for coeliac disease among irritable bowel syndrome patients: analysis of cost-effectiveness and value of information. Eur J Health Econ 2013;14(6):947-957

12. Mein S M, Ladabaum U. Serological testing for coeliac disease in patients with symptoms of irritable bowel syndrome: a cost-effectiveness analysis. Aliment Pharmacol Ther 2004;19(11):1199-1210