Platelet-Rich Plasma (PRP) Preparation Protocol

What PRP Is

PRP is an autologous blood product prepared by centrifuging a patient's own blood to concentrate the platelet fraction (typically 3-5x baseline platelet concentration) along with associated growth factors, released from centrifuged peripheral blood - Rheumatology, 2-Volume Set (2022, Elsevier), p. 3511. It is used across orthopedics (tendinopathy, osteoarthritis), dermatology (alopecia areata, skin rejuvenation), and ENT.

Standard Preparation Steps

1. Patient evaluation and consent Screen for contraindications (active infection, malignancy, thrombocytopenia/platelet dysfunction, anticoagulant therapy, severe anemia).

2. Blood draw Venous blood (typically 10-60 mL depending on protocol/kit) is collected into tubes containing an anticoagulant (usually sodium citrate) to prevent premature clotting and platelet activation.

3. First ("soft") spin - plasma separation Whole blood is centrifuged at low speed (roughly 100-270 x g for 5-10 minutes in published protocols) to separate red blood cells from the plasma/buffy coat layer. This produces three layers: RBCs at the bottom, a buffy coat (platelets + leukocytes) in the middle, and plasma on top. Centrifugation force, time, tube size, and blood volume all affect final platelet yield.

4. Second ("hard") spin - platelet concentration The plasma and buffy coat are transferred to a new tube and re-spun at a higher speed (commonly cited ranges ~1000-3000 x g for 5-15 minutes) to pellet the platelets. The upper fraction becomes platelet-poor plasma (PPP); the lower fraction, resuspended in a small plasma volume, is the final PRP. Some commercial kits use a single-spin process instead of this double-spin method.

5. Classification / composition check PRP preparations vary by:

Leukocyte content: leukocyte-rich PRP (LR-PRP) vs leukocyte-poor PRP (LP-PRP)
Activation status: activated (with calcium chloride/thrombin, triggering immediate growth factor release) vs non-activated
Platelet concentration factor relative to baseline whole blood

This is clinically important, since orthopedic literature notes composition and protocol reporting is frequently inconsistent between studies (see evidence note below).

6. Quality check Platelet count verification and sterility confirmation before use.

7. Optional activation Some protocols activate the PRP just before injection (calcium chloride, thrombin, or mechanical) to trigger degranulation and immediate growth factor release; others rely on in-vivo activation by contact with collagen/tissue at the injection site.

8. Administration Injected at the treatment site (e.g., intra-articular for knee OA, peritendinous for tendinopathy, intradermal/intrafollicular for alopecia areata) or applied topically, usually immediately after preparation to preserve platelet viability.

Related technique: PRF (Platelet-Rich Fibrin)

Distinct from PRP - uses no anticoagulant, is centrifuged immediately after the draw (classic protocol ~408 x g for 12 min), and fibrin polymerizes during spinning to trap platelets/leukocytes in a solid/gel matrix rather than a liquid concentrate.

Textbook-Documented Clinical Uses

Osteoarthritis / tendon injury: PRP injected to recruit platelet growth factors and promote tissue repair, though structural benefit over placebo remains unproven - Rheumatology, 2-Volume Set, p. 3511-3519; Campbell's Operative Orthopaedics 15th Ed, p. 1041-1047.
Alopecia areata: used as monotherapy or adjunct; one double-blind trial showed superiority over low-dose intralesional triamcinolone and placebo - Fitzpatrick's Dermatology Vol 1&2, p. 1549.
Fracture/bone regeneration: discussed as a regenerative adjunct in Rockwood and Green's Fractures in Adults, 10th ed, p. 2083.
Blood banking context: PRP is also an intermediate product in platelet component manufacturing (separated by slow-speed spin, then high-speed spin of the PRP) - Harrison's Principles of Internal Medicine 22E, Table 118-1, p. 1064.

Evidence Caveats (Recent Literature)

A 2025 systematic review (Lim et al., Arthroscopy, PMID 38522650) found that most orthopedic PRP studies fail to report their preparation protocol and final composition, making cross-study comparison and true protocol standardization difficult. This is a major limitation when trying to define "the" PRP protocol - results are highly dependent on the specific device/spin parameters used.
A 2025 network meta-analysis (Yu et al., J Orthop Surg Res, PMID 40551225) compared different PRP preparation protocols specifically for knee osteoarthritis and found efficacy varies by preparation type (leukocyte content, activation, number of injections) - supporting the idea that "PRP" is not a single standardized product but a family of protocols with different clinical effects.
The Rheumatology textbook also flags that recent placebo-controlled trials failed to show efficacy for PRP in knee and ankle OA, consistent with ongoing controversy despite promising early reports.

Practical takeaway: there is no single universally-mandated PRP protocol. Centrifugation speed/time, single vs double spin, anticoagulant choice, activation method, and leukocyte content should be selected and reported based on the specific clinical indication and the commercial kit/device being used, since these variables measurably change the final platelet and growth factor concentration delivered to the patient.

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