Testing for coeliac disease rarely leads to a diagnosis: a population-based study

Figures & data

Figure 1. Figure one depicts the search string that was used to find eligible cases. Three techniques were used that to find cases both separate from each other or combined (and/or). In free text annotations, in the ICPC coding system and in laboratory test results. TTG: tissue Transglutaminase, HLA: human leukocyte antigen, ICPC: International Classification of Primary Care, D99.06: code for coeliac disease diagnosis.

Figure 2. Flowchart of search strategy and patient selection based on general practice contacts in 2016 related to gluten or coeliac disease in a cohort of 207.200 patients distributed over 49 general practices and distribution of diagnosis in the included study population (n = 1972). ICPC-1: International Classification of Primary Care, D99.06: ICPC-1 code for coeliac disease, GP: general practitioner, CD: coeliac disease, NCGS: non-coeliac gluten sensitivity, tTGA: tissue Transglutaminase antibodies, GDS: gastroduodenoscopy. *1: Number of patients registered in 49 of the general practices associated with the Academic network of general practice at VU University Medical Centre in 2016, *2 patients with a confirmed diagnosis out of all patients that were referred to a specialist.

Table 1. Baseline characteristics of all patients (n = 1972) with at least one coeliac disease or gluten-related general practice contact in 2016.

Variables	Study population (gluten- or coeliac disease related contact in 2016 (n)	%	Serological test performed in observation period (n)	%	Newly diagnosed coeliac disease (n)	%
Patients	1972	100	1305 ^a	65.9	21	1.1
Gender, female	1326	67.2	867	66.4	13	61.9
Age, mean (95% CI)^b	30.8 (13.3–48.0)		31.5 (30.6–32.4)		21.3 (12.3–30.3)
<22	536	27.2	328	25.1	13	61.9
22-30	545	27.6	359	27.5	1	4.8
31-45	525	26.6	368	28.2	4	19.0
>46	366	18.6	250	19.2	3	14.3
Reported relatives with coeliac disease	65	3.3	46	3.5	3	14.3

In the second column all patients in that group that were serologically tested for coeliac disease (n = 1305) are characterised. The last column exhibits the characteristics of all patients that tested positive for CD (n = 21).

^aIncluding five patients that were previously diagnosed with coeliac disease; CI: confidence interval, ^bage at time of contact based on year of birth, CD: coeliac disease.

Table 2. Recorded main reason for CD-or gluten related contact in 2016, and the frequency of serological testing and positive test results in the study population (n = 1972).

Reported main reason for consultation
	Total = 1972		serologically tested = 1305		Positive test result = 21
	N	%^a	N	%^a	N	%
Gastrointestinal	1418	71.9	964	74.8	14	4.3
Stomach ache/cramps	600	30.4	409	68.2	8	2
Diarrhoea	264	13.4	178	67.4	1	0.6
Changing bowel habits	145	7.4	104	71.7	2	1.9
Distension	143	7.3	98	68.5		0
Constipation	81	4.1	52	64.2		0
Non-specific	68	3.4	48	70.6	1	2.1
Nausea	43	2.2	31	72.1	1	3.2
Flatulence	40	2	26	65		0
Rectal blood loss	23	1.2	9	39.1		0
Reflux	5	0.3	3	60		0
Vomiting	2	0.1	2	100	1	50
Borborygmi	2	0.1	2	100		0
Fecal incontinence	1	0.1	1	100		0
Viscous stool	1	0.1	1	100		0
General symptoms	201	10.2	132	50.1	2	0.5
Fatigue	114	5.8	77	67.5		0
Weight loss	30	1.5	23	76.7	2	8.7
Anaemia	26	1.3	15	57.7		0
Weight gain	8	0.4	6	75		0
Growth retardation	8	0.4	2	25		0
Dizziness	2	0.1	2	100		0
Syncope	2	0.1	1	50		0
General malaise	2	0.1	2	100		0
Arthralgia	2	0.1	2	100		0
Excessive Perspiration	1	0.1	1	100		0
Insomnia	1	0.1	0	0		0
Vitamin B deficiency	1	0.1	0	0		0
Hematuria	1	0.1	1	100		0
Angioedema	1	0.1	0	0		0
Asthmatic complaints	1	0.1	0	0		0
Dental problems	1	0.1	0	0		0
Neurological	12	0.6	9	46.3		0
Headache	9	0.5	8	88.9		0
Tingling sensations	2	0.1	1	50		0
Neuropathy	1	0.1	0	0		0
Dermatological	63	3.2	34	60.2		0
Pruritus	23	1.2	14	60.9		0
Eczema	22	1.1	9	40.9		0
Aphthous stomatitis	5	0.3	3	60		0
Other oral cavity abnormalities	4	0.2	2	50		0
Acne	2	0.1	0	0		0
Psoriasis	2	0.1	1	50		0
Exanthema	2	0.1	1	50		0
Rosacea	1	0.1	1	100		0
Alopecia	1	0.1	1	100		0
Lichen Sclerosus	1	0.1	1	100		0
Exanthema	2	0.1	1	50		0
Reported Family History CD	40	2	29	72.5	2	6.9
Fear of CD	20	1	14	70
Hypothyroid Disease	10	0.5	8	80
Ophthalmic	3	0.2	3	100
Not reported	205	10.4	113	55.4	3	2.8
Total	1972	100	1305	66.3	21	1.6

^aPercentage of total number of patients with CD or glutenrelated contacts for this registered main reason for contact in 2016; CD: coeliac disease.

Figure 3. Heterogeneity between general practices (n = 49) in the numbers of patients with at least one coeliac disease or gluten-related contact in 2016 and in the diagnostic approach. Patients that were diagnosed before 2016 were excluded from analysis. On the horizontal axis the participating practices are numbered arbitrarily from 1 to 49. The left vertical axis shows the number of patients that had at least one CD-related contact in 2016. The right vertical axis depicts the percentage of these patients that got tested for CD (orange/upper line) in 2016, and the percentage of these tested patients that were diagnosed with CD (black/lower dotted line). CD: coeliac disease.