Table 4.

Causes of false-negative and false-positive registration of cancer diagnoses in the electronic health records

Number	Per cent	Comments
False-positive diagnoses
59	49	No explanation
59	49	No logical reason can be traced in the full EHR text about the registration of a cancer code with this patient
15	13	Coding error by GP
15	13	Coding error by GP (eg, ‘R84’ lung cancer when lung cancer is suspected by the GP)
46	38	Diagnosis correct in EHR
16	13	Year of diagnosis in the EHR is 2011, leaving a small chance that the histological confirmation of the diagnosis (NCR) was performed (and registered) in 2012, while the clinical diagnosis was made and registered in the EHR in 2011
11	9	Year of diagnosis >10 years before 2007; cancer not available in the NCR
8	7	Cancer registered twice at GP
7	6	Patient has moved or diagnosis was made abroad, thus not in the NCR
4	3	No tissue biopsy was performed in agreement with patient and/or family, thus not in the NCR
120	100
False-negative diagnoses
92	77	Information about cancer is available
35	29	Information about cancer is available in plain text in the EHR but cancer is not coded
27	23	GP assigned a wrong code/did not update existing code after diagnosis (eg, ‘X19’ lump in breast instead of ‘X76’ breast cancer)
20	17	Cancer is coded in the EHR but GP assigned a year of diagnosis >2011
10	8	Coded cancer found in full EHR but patient was not in the initial search due to time lapse between the initial search and linkage (>1 year)
16	13	EHR record cannot be retrieved
16	13	Patient EHR cannot be retrieved (probably linkage error)
10	8	No explanation
10	8	No EHR text or codes about any cancer
2	2	Various
2	2	Remaining causes: patient has moved, diagnosis after death
120	100

EHR, electronic health record; GPs, general practitioners; NCR, Netherlands Cancer Registry.