Implications of the problem orientated medical record (POMR) for research using electronic GP databases: a comparison of the Doctors Independent Network Database (DIN) and the General Practice Research Database (GPRD)

Table 3 Comparison of record length in the DIN and GPRD birth cohorts

	DIN					GPRD
	1989–93 births (n = 20,149)	1994–97 births (n = 20,034)	1989–1997 births (n = 40,183)			1989–93 births (n = 76,310)
	Mean	Mean	Mean	Median	IQR	Mean	Median	IQR
No. of days with a prescription issued	19.6	19.4	19.5	14	8–24	19.8	15	9–26
No. of days with diagnostic codes	15.8	15.7	15.8	13	8–21	22.9	20	13–30
No. of days with diagnostic codes or drugs linked to existing diagnostic codes	23.0	23.2	23.1	18	10–30	_	_	_
No. of days with either diagnostic or drugs or both codes	25.9	26.0	26.0	20	12–33	27.4	23	14–35

– mean number of events in the first 5 years of life averaged across all individuals – median number of events in the first 5 years of life across all individuals – lower and upper quartiles of number of events in the first 5 years of life across all individuals

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