Table 2.

Recall and precision of temporal extraction algorithm

	Gold standard	True positives	False positives	False negatives	Recall	Precision	F measure
Past dates	373	349	10	14	0.93	0.97	0.95
Specified	297	285	3	7	0.96	0.99	0.97
Relative	78	64	7	7	0.82	0.90	0.86
Future dates	123	101	8	14	0.82	0.93	0.87
Specified	30	19	2	9	0.63	0.90	0.75
Relative	93	82	6	5	0.88	0.93	0.91
Recurring dates	13	9	0	4	0.69	1.00	0.82
Present dates	29	29	0	0	1.00	1.00	1.00
Totals	538	488	25*	32	0.91	0.95	0.93

True positives represent dates correctly identified and assigned to individual colonoscopy concepts. Specified dates are any explicit date formats (eg, ‘3/06’, ‘early 1990s’). Relative dates include any reference that requires a calculation (eg, ‘5 years ago’, ‘last Monday’).

^*Seven false positives were identified from sentences without a colonoscopy date (n=670).