Table 4.

Subgroup analyses of respondents and non-respondents at 2 year

Outcome a	I. Respondents n = 491 (77.6%)		II. Non-respondents n = 138 (21.8%)		III. Consistent non-respondents b n = 11		p-value of difference
							I vs. II	I vs. III
EQ-5D score c	0.46 (0.36–0.60)	< 0.001	0.41 (0.30–0.64)	< 0.001	0.64 (0.19–0.76)	0.003	0.8	0.6
Health state d	31 (28–34)	< 0.001	27 (22–32)	< 0.001	28 (13–43)	0.002	0.1	0.7
Leg pain d	40 (37–43)	< 0.001	44 (38–50)	< 0.001	43 (25–61)	0.001	0.3	0.8
Back pain c	22 (18–28)	< 0.001	26 (17–32)	< 0.001	40 (17–66)	0.008	1.0	0.3
Benefited from the operation, n (%) e	447 (91)		124 (91)		11 (100)		0.8	0.3
Received workers compensation, n (%) f	141 (29)4		0 (29)		4 (36)		1.0	0.6

^a Improvements from baseline (absolute values) are shown.

^b Group III is a subgroup of group II.

^c Median change, (95% CI) and p-value

^d Mean change, (95% CI) and p-value

^e Patients who stated that they had “some”, “much”, or “very much” benefit from the operation.

^f Patients who were on full or partial sick leave, on rehabilitation, or disability pensioners.