Description and initial evaluation of incorporating electronic follow-up of study participants in a longstanding multisite cohort study

Table 1 Median (interquartile range; IQR) number of contacts required for completion of follow-up by use of electronic questionnaire and type of follow-up among CARDIA participants at the Chicago field center

	Last follow-up before eCARDIA pilot	Follow-up during eCARDIA pilot	P-value^**
	Median (IQR)	Median (IQR)
Contact information follow-up*
Follow-up completed using electronic questionnaire (n = 336)	1 (1 – 3)	1 (1 – 2)	0.0002
People who completed follow-up using another mode (n = 341)	3 (1 – 4)	3 (2 – 4)	0.0009
People who did not complete follow-up (n = 20)	4 (3 – 6)	8 (7 – 9)	0.004
Medical conditions follow-up*
Follow-up completed using electronic questionnaire (n = 361)	1 (1 – 3)	2 (1 – 3)	0.47
People who completed follow-up using another mode (n = 302)	3 (1 – 5)	4 (2 – 5)	0.0001
People who did not complete follow-up (n = 34)	6 (3 – 11)	9 (7 – 12)	0.02

^*P < 0.0001 comparing the three categories of follow-up based on the Kruskal-Wallis test
^**P-value comparing participant contacts before and after eCARDIA based on the Wilcoxon signed rank sum test

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