Clinical effect modifiers of antibiotic treatment in patients with chronic low back pain and Modic changes - secondary analyses of a randomised, placebo-controlled trial (the AIM study)

Table 2 Distribution of the potential effect modifiers according to treatment groups

	Amoxicillin (n = 89) Number of patients	Placebo (n = 91) Number of patients
Primary effect modifiers
Modic changes type I
Yes	58	60
No	31	31
Missing	0	0
Previous disc surgery
Yes	18	20
No	71	71
Missing	0	0
Pain provocation test
Negative	15	10
Positive	74	81
Missing	0	0
CRP
< 5 mg/L	70	82
≥ 5 mg/L	14	7
Missing	5	2
Exploratory effect modifiers
Disturbed sleep
No	42	47
Yes	46	42
Missing	1	2
Pain characteristics
Fluctuating	70	63
Constant	19	26
Missing	0	2
Duration of low back pain
< 2 years	31	25
≥ 2 years	58	65
Missing	0	1
Age
< 40 years	28	27
≥ 40 years	61	64
Missing	0	0
Gender
Male	36	39
Female	53	52
Missing	0	0

CRP C-reactive protein
ODI Oswestry Disability Index. Score from 0 to 100. Higher scores indicate more severe pain and disability

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