Investigations

1st investigations to order

FBC and blood smear

Test
Result
Test

Iron deficiency anaemia is the most common clinical presentation in adults.

Folate (and rarely vitamin B12) deficiency may lead to a macrocytic anaemia. [42]

Result

low Hb and microcytic red cells

immunoglobulin A-tissue transglutaminase (IgA-tTG)

Test
Result
Test

Order an IgA-tTG test in any patient with suspected coeliac disease. [34]

Higher titres have increased positive predictive value. Serological testing should be done on a gluten-containing diet.

Result

titre above normal range for laboratory

endomysial antibody (EMA)

Test
Result
Test

EMA is a more expensive alternative to IgA-tTG with greater specificity but lower sensitivity.

Perform initially if IgA-tTG is unavailable.

Result

elevated titre

skin biopsy

Test
Result
Test

Order this test initially in any patient with skin lesions suggestive of dermatitis herpetiformis.

Both sensitivity and specificity are high.

Result

granular deposits of IgA at the dermal papillae of lesional and perilesional skin by direct immunofluorescence

IgG DGP (deamidated gliadin peptide) or IgA/IgG DGP

Test
Result
Test

Test of choice for individuals with IgA deficiency.

Result

elevated titre

IgG-tTG

Test
Result
Test

IgG-tTG was previously one of the common serological tests for coeliac disease in individuals with known or suspected IgA deficiency. However, this test has been largely replaced by the newer and more accurate IgG DGP or IgA/IgG DGP (deamidated gliadin peptide).

Result

elevated titre

small bowel - macroscopic

Test
Result
Test

The endoscopic appearance is not sensitive for diagnosis. com.bmj.content.model.Caption@7d0bcf68 [Figure caption and citation for the preceding image starts]: Scalloping of the duodenal mucosa in a patient with coeliac disease From the personal collection of D.A. Leffler; used with permission [Citation ends]. com.bmj.content.model.Caption@2b032916 [Figure caption and citation for the preceding image starts]: Scalloping of the duodenal mucosa in a patient with coeliac disease From the personal collection of D.A. Leffler; used with permission [Citation ends].

Result

atrophy and scalloping of mucosal folds; nodularity and mosaic pattern of mucosa

small bowel - histology

Test
Result
Test

Small-bowel histology is essential and the gold-standard test to confirm the diagnosis.

Two biopsies of the bulb and at least four biopsies of the distal duodenum should be submitted for histological analysis.

If possible, grade the results according to the Marsh criteria. Perform small-bowel histology in patients with positive serology or IgA deficiency or if there is high clinical suspicion despite negative serology. Biopsies should be performed while on a gluten-containing diet.

Paediatric patients with symptoms consistent with coeliac disease and a high IgA-tTG titre (above normal range for laboratory) may go on to have confirmatory EMA and HLA-DQ2/-DQ8 testing. If both of these are positive, coeliac disease may be considered confirmed without a small intestinal biopsy. [38]

Both sensitivity and specificity are high. com.bmj.content.model.Caption@6bd9583d [Figure caption and citation for the preceding image starts]: Histological image of small intestinal villous atrophy and crypt hyperplasia From the personal collection of D.A. Leffler; used with permission [Citation ends]. com.bmj.content.model.Caption@4d60c4be [Figure caption and citation for the preceding image starts]: Histological image of small intestinal villi showing resolution of intestinal injury on gluten-free diet From the personal collection of D.A. Leffler; used with permission [Citation ends].

Result

presence of intra-epithelial lymphocytes, villous atrophy, and crypt hyperplasia

Investigations to consider

human leukocyte antigen (HLA) typing

Test
Result
Test

This genetic test is useful to rule out coeliac disease in patients already on a gluten-free diet or in patients with an idiopathic coeliac-like enteropathy.

Result

positive HLA-DQ2 or HLA-DQ8

gluten challenge

Test
Result
Test

People with coeliac disease on a gluten-free diet prior to evaluation cannot be differentiated from healthy controls. In these patients, gluten challenge is necessary. In a gluten challenge, the person is placed back on a gluten-containing diet, with serological tests and small bowel histology assessed after 2 to 8 weeks on the gluten-containing diet. [40]

Result

increase in coeliac serological tests and presence of intra-epithelial lymphocytes, villous atrophy, and crypt hyperplasia on small intestinal biopsy

Emerging tests

saliva coeliac genetic test

Test
Result
Test

It is important to counsel that having HLA-DQ2 or HLA-DQ8 is not equivalent to having coeliac disease, and having these genes alone does not have any known prognostic value. If this test is negative, a person's risk for coeliac disease is extremely low.

Result

positive or negative for either HLA-DQ2 or HLA-DQ8

Use of this content is subject to our disclaimer