Table 1. Serum concentration of substance P and severity of chronic pain in both groups of patients.

Parameter/group	OA			RA			P-value
	Mean ±SD	Min	Max	Mean ±SD	Min	Max
SP, pg/ml	327±290	46	1000	563±425	50	1500	0.016
NPS, points	3.0±0.8	2	4	3.1±0.8	2	4	0.582