Table 1.

Characteristics of primary care registry databases that will be approached for this study

Name of database	Country	Number of patients	Data coding	Free text available	Linkage to hospital data available	Estimated number of SVT casesa	Intended use of database: development/validation
Intercity Consortium [14]	The Netherlands	1M	ICPC codes	Yes	No	13,100	Validation
Pharmo General Practitioner Database [15]	The Netherlands	2.5M	ICPC codes	Yes	Yes	32,750	Validation
SAIL databank [16]	Wales	3.5M	Read codes	No	Yes	45,850	Validation
CPRD Gold and Aurum [17]	England	50M	Read and Snowmed codes	No	Yes	655,000	Development

^aBased on an incidence rate of 1.31 per 1000 person-years and the assumption of 10 years follow-up [3]

ICPC International Classification of Primary Care