Table 3.

Prevalence estimates by subgroup

	Studies, n	Studies with prevalence estimates, n	Median prevalence, %	IQR, %	Ratio of 75th to 25th percentile
Overall	59	40	4·91	2·64–11·51	4·36
Features of algorithms used to identify AD patients
Diagnosis code category
Limited to AD	35	26	4·30	2·14–6·70	3·13
AD plus others	23	13	11·53	9·20–30·23	3·29
Algorithm included number of visits/codes
Required multiple occasions	8	8	4·27	3·85–5·61	1·46
No	50	31	5·60	2·24–12·37	5·52
Algorithm specified the type of provider associated with a code
Yes	5	5	4·53	4·39–6·70	1·53
No	53	34	4·91	2·50–11·50	4·60
Algorithm included prescription data
Yes	5	3	16·93	12·37–32·49	2·63
No	54	37	4·53	2·50–10·94	4·38
Study characteristics
Age of patient population
Children only	32	19	10·94	4·69–19·00	4·05
Adults +/− children	27	21	3·80	2·14–5·60	2·62
Continent
Europe	28	21	10·35	3·80–16·93	4·46
North America	8	4	6·05	2·85–9·05	3·18
Asia	21	15	4·39	2·21–6·70	3·03
Type of routinely collected data
National patient register	3	1	12·37	n/a	n/a
Administrative database	34	26	4·27	2·24–6·70	2·99
Primary care database	15	11	13·24	2·79–31·40	11·25
Hybrid	4	2	6·81	4·42–9·20	2·08
Terminology
Atopic dermatitis	31	21	4·69	2·24–10·94	4·88
Atopic dermatitis/eczema	3	2	2·85	2·50–3·20	1·28
Atopic eczema	5	4	3·85	2·25–7·13	3·17
Eczema	17	13	11·50	4·42–30·23	6·84
Prevalence calculation
Time period
1‐year period prevalence	9	9	2·79	2·24–3·43	1·53
Multiyear period prevalence	29	29	8·90	4·15–13·21	3·18

IQR, interquartile range; AD, atopic dermatitis; n/a; not applicable.