Table 2.

Missing items and success of obtaining items by telephone follow-up.

Measure (total number of items)	Baseline				Four months				Six months
	Items missing		Items obtained by telephone follow-up		Items missing		Items obtained by telephone follow-up		Items missing		Items obtained by telephone follow-up
	n	%	N	%	n	%	n	%	n	%	n	%
Intermittent and Constant Osteoarthritis Pain scale	0/550	0	N/Aa	N/Aa	16/330	5	11/16	69	11/275	4	11/11	100
Western Ontario and McMaster Universities Osteoarthritis Index	56/1200	5	49/56	88	33/720	4.5	24/33	72	31/600	4	24/31	77
Beck Depression Inventory	4/1050	0.4	0/4	0	42/630	7	21/42	50	43/525	8	0/21	0
Beck Anxiety Inventory	4/1050	0.4	¼	25	42/630	7	21/42	50	43/525	8	0/21	0
EQ-5D-5 L™	5/300	2	2/5	40	2/180	1	0/2	0	0/150	0	0	0
Total	0		52		4		77		6		35

The numerator is the total number of items missing, the denominator is the total number of items for the whole dataset at that time point (at baseline n = 50, at four months n = 30, and at six months n = 25).

^aN/A because there were no missing data at this time point for this scale. The numerator is the amount of items that were collected over the telephone; the denominator is the total number of missing items for that scale for that time point. The percentage reflects the amount of missing data that could be obtained over the telephone.