Table 2.

Data collection and classification of reviewed medical records, annual incidence of GP-reported Lyme carditis diagnoses per 10 million inhabitants and annual total numbers among the 16.6 million inhabitants of the Netherlands in 2009 and 2010

Incidence questionnaire sent to GPs	N	(% of 9178)
Response to question on Lyme carditis	3067	(33.4 %)
GP practice population	7,682,803
Reports of diagnosed Lyme carditis	39
Annual incidence of Lyme carditis in 2009 and 2010 per 10 million inhabitants, based on 39 GP reports of Lyme carditis per 7,682,803 practice population
Crude incidence for Lyme carditis	25	(95 % CI: 18–34)/10,000,000
Medical record review	N	(% of 22)
Response on GP reported cases	22
GP unable to recall identity	7	(31.8 %)
Unwilling to cooperate	4	(18.2 %)
Invalid reports of Lyme carditis	3	(13.6 %)
Medical records reviewed	8	(36.4 %)
Classification of reviewed medical records	N	(% of 11)
Very likely diagnosis	6	(54.5 %)
Likely diagnosis	1	(9.1 %)
Possible diagnosis	–
Not Lyme carditis	1	(9.1 %)
Invalid report of Lyme carditis, not reviewed	3	(27.3 %)
Clinical presentation within 2009 or 2010	N	(% of 8)
	3	(37.5 %)
Adjusted a annual incidence of Lyme carditis in 2009 and 2010 per 10 million inhabitants
Incidence for Lyme carditis	6	(95 % CI: 4–8)/10,000,000
National numbers	10

95 % CI: 95 % confidence intervals.

^aAdjusted for 63.6 % very likely + likely diagnoses, and for 37.5 % clinical presentations within the targeted period of 2009 or 2010.