(b).

Volume of whole blood	Volume of PRP injected	Number of injections during the study period	Study period	Pain scores evaluated in the study
200 ml	2 ml	Single	6 m	VAS RDQ
9 ml	2 ml	Single	2-10 m	NRS ODI
60 ml	1.5-3 ml	Single	24 w	VPS
30 or 60 ml	1.5 ml	Single, at one or multiple levels	6 m	VAS ODI
30 ml	1-2 ml	Single, at one or multiple levels	8 w	FRi, NRS, SF-36, and modified NASS
200 ml	2 ml	Single	10 m	VAS RDQ
Not mentioned	1.5 ml	Single	12 m	Improvement T2 nuclear signal intensity↑

Abbreviations: ACT: activation; BDI: Beck Depression Inventory; DPQ: Dallas Pain Questionnaire; FRI: functional rating index; L-PRP: leukocyte- and platelet-rich plasma; m: months; NRS: numerical rating scale; ODI: Oswestry Disability Index; P-PRP: leukocyte-poor PRP; PRP: platelet-rich plasma; RDQ: Roland-Morris Disability Questionnaire; SF: short form; SF-MPQ: short-form McGill Pain Questionnaire; vPS: verbal pain scale; w: weeks; VAS: visual analog scale; NASS: North American Spine Society.