Table 4.

Association between selected biomarkers and demographic or clinical variables.

	Age		HIV status		QFN result		Back pain duration		Constitutional symptoms		ODI category
	rs	p-value	MW	p-value	MW	p-value	rs	p-value	MW	p-value	χ2	p-value
Fibrinogen	-0.16	0.32	138	0.30	54	0.01*	-0.55	<0.001*	96	0.002*	10.0	0.04*
CRP	-0.11	0.47	128	0.19	67	0.05	-0.57	<0.001*	116	0.01*	9.10	0.06
IFN-γ	-0.08	0.63	112	0.06	56	0.01*	-0.49	<0.001*	158	0.11	9.99	0.04*
NCAM	-0.28	0.07	139	0.32	60	0.03*	-0.43	0.004*	85	<0.001*	2.92	0.57
Ferritin	0.27	0.09	171	0.98	91	0.27	-0.33	0.03*	179	0.30	4.09	0.39
CCL1	-0.28	0.07	103	0.04*	83	0.17	-0.14	0.37	162	0.15	3.48	0.48
IL-10	-0.21	0.18	125	0.13	93	0.25	-0.19	0.22	200	0.58	1.98	0.74

r^s, Spearman’s rho; MW, Mann-Whitney U statistic; χ², Kruskal-Wallis statistic. Demographic and clinical variables were selected based on a difference between back pain groups at p < 0.10. The association between biomarkers and these variables was investigated as follows: Spearman’s correlation for continuous variables age and back pain duration; Mann-Whitney U test for binomial variables HIV status, quantiferon (QFN) result and constitutional symptoms; Kruskal-Wallis test for categorical variable Oswestry Disability Index (ODI) category. Only confirmed results were included in the HIV and QFN analyses (n = 15 HIV positive, n = 23 HIV negative) (n = 27 QFN positive, n = 9 QFN negative). *Significant at p < 0.05.