Months of bloating, a GP conversation, and then a booking for a coeliac test at Blood London. On the order sits a second line that looks out of place: total IgA.
It belongs there, because the standard coeliac antibody test is an IgA test, and in someone who makes very little IgA it can read normal when coeliac antibodies are present. At Blood London, our coeliac profile measures total IgA alongside it every time, which tells the doctor whether the coeliac result can be relied on. IgA is an antibody, one of the three main classes in the blood alongside IgG and IgM.
You can walk in at 117a Harley Street seven days a week: Monday to Friday 09:00 to 18:00, Saturday and Sunday 10:00 to 14:00. The Coeliac/Gluten Sensitivity Profile is £246.25 plus the £50 blood draw, with results in about 3 days.
Before the visit, keep gluten in your diet. Coeliac UK advises including at least 3g, preferably 6g, of gluten every day for at least six weeks before testing, and carrying on until all tests are complete.
"When someone is tested for coeliac disease, I want their total IgA as well. A few people make very little IgA, and then the usual coeliac antibody test can look normal when it isn't."
Dr Scott Pereira, Consultant Immunologist, GMC 1524080
What happens to a coeliac sample, step by step
At Blood London, a coeliac sample follows the same order every time. The sample is taken at 117a Harley Street and reaches the lab the same day, and the turnaround clock starts there.
- Step 1: three measurements from one sample. The Coeliac/Gluten Sensitivity Profile always includes total IgA, tTG IgA and deamidated gliadin IgG, so total IgA is measured every time.
- Step 2: tTG IgA, the main coeliac marker. Tissue transglutaminase IgA is read alongside the total IgA. When IgA is normal, tTG IgA is the result that answers the coeliac question.
- Step 3: if IgA is low, gliadin IgG takes over. A person with low IgA cannot show a strong IgA-based result, so the deamidated gliadin IgG result answers it instead. It is the coeliac marker that still works when IgA is low.
- Step 4: if tTG IgA is positive or borderline, endomysial IgA confirms it. The endomysial antibodies IgA test checks the same question a second way before anyone draws a conclusion.
- Step 5: the report. Results are emailed in about 3 days, a little longer if a confirmatory test is needed. An optional Blood London doctor review is £75 and can be added to any test.
Booking tTG IgA on its own works differently: when that result is very low, the lab checks total IgA, because a very low tTG can mean no coeliac antibodies or very little IgA.
A raised antibody result is a reason to speak to a doctor about next steps. A blood test alone does not diagnose coeliac disease.
Reading your IgA result
The reference range printed on your report is the one to use, because ranges differ between laboratories and with age.
A low total IgA is called IgA deficiency. It is common, and many people with it have no symptoms and find out only when a coeliac test is done.
A raised IgA can reflect ongoing inflammation or infection. A doctor reads it alongside your other results and your symptoms, which is why a single number out of range is a starting point for a conversation.
What each piece costs
- Total IgA alone: £56.25, results in 1 day.
- tTG IgA alone: £86.25, results in 3 days.
- The two bought separately: £142.50.
- The Coeliac/Gluten Sensitivity Profile: £246.25, which adds deamidated gliadin IgG.
Every option carries one £50 draw per visit, however many tests you take. The profile costs £103.75 more than the two tests alone, and the extra buys the backup marker for low IgA. Anyone with a recent normal total IgA may only need tTG IgA. Someone starting from scratch usually saves a second visit with the profile.
The other reason people test IgA
Frequent chest infections, sinus infections that keep returning or a doctor's note about immune function lead to the second use of IgA. Here it is read with IgG and IgM, which is the job of the immunoglobulins IgG, IgM and IgA test. At £113.13 with results in 1 day, it measures all three main antibody classes together and gives a general picture of immune function.
If you would rather talk the result through face to face, Medical Express Clinic offers GP appointments at the same address. Antibody results sit best beside a general count of cells, so the full blood count guide is a useful companion read, and our page on fasting before a blood test covers preparation on the day.
What does low IgA mean?
Low IgA means the body is making less of this antibody than expected. It can be a lifelong feature without symptoms, or it can sit alongside repeated infections. At Blood London, its main effect on a coeliac test is that tTG IgA may under-read, which is why gliadin IgG is used.
Can I test IgA on its own without a coeliac test?
Yes. The IgA test is available alone at £56.25 plus the draw, and the IgG, IgM and IgA combination suits anyone looking at immune function more widely.
How soon will my results arrive?
Total IgA and the three-antibody combination return in 1 day. tTG IgA, the endomysial test and the coeliac profile take up to 3 days, counted from when the sample reaches the lab.
Book an IgA or coeliac test
Walk in to 117a Harley Street any day, or start with the Blood London home page to choose your test. Results are emailed to you, and a doctor review is there if you want one.