Standardising PRP Preparation: Variables That Change the Product

Ask five clinics to describe their PRP preparation protocol and you will hear five kit brand names, a centrifuge speed quoted in rpm with no rotor radius attached, and at least one confident "we double-spin" with no numbers behind it. None of that is a protocol. A PRP preparation protocol is a manufacturing specification: draw volume, anticoagulant, tube system, force and time for each spin, which fractions are kept, what volume the platelets end up in, and the longest acceptable interval between draw and injection. Change any one of those and you have changed the product.

The trials that give PRP for androgenetic alopecia its credibility were run on defined, repeatable preparation methods — Gentile's randomised half-head trial and Alves and Grimalt's double-blind study both specified their processing before the first patient was bled. A clinic that cannot state its own parameters cannot borrow those results as a benchmark, cannot troubleshoot a cluster of non-responders, and cannot tell whether a new technician has quietly changed what goes into the syringe.

What a PRP preparation protocol must specify#

One page is enough, provided every line carries a number. The working minimum: whole-blood draw volume (10–30 mL covers most scalp work); anticoagulant and ratio (ACD-A or 3.2% sodium citrate at roughly 1:9); the centrifuge by model and rotor radius; force in g and duration for each spin, with the brake setting; whether the buffy coat is included or excluded; the plasma fraction discarded; the final product volume; the maximum draw-to-injection interval; and the platelet-count cadence used to verify all of the above.

Two things about that list are routinely missed. First, it names hardware. A protocol written for a swing-out rotor does not transfer unchanged to a fixed-angle machine, because the separation geometry differs and the cell layers sit tilted. Second, the document has an owner. Someone — usually the lead nurse or the physician running the programme — signs changes, dates versions and files it alongside the clinic's other operating documents, exactly as described in our guide to clinic SOPs. An unowned protocol decays into folklore within a quarter.

Spin force and time: g, not rpm#

Revolutions per minute is not a unit of separation. Relative centrifugal force depends on rotor radius and the square of rotor speed, so two centrifuges both set to 3,000 rpm can apply forces that differ by nearly a factor of two. Every figure in your prp spin protocol should be written in g, with the rpm equivalent for your specific machine noted beside it.

Convention across published methods and kit inserts clusters in predictable bands: a soft first spin of roughly 100–300 g for 5–10 minutes to sediment red cells, and — in double-spin methods — a harder second spin of roughly 400–700 g for 10–15 minutes to pellet platelets, which are then resuspended in a fraction of the plasma. Pushing force well beyond those bands does not buy proportionate yield; it costs yield, through premature activation and platelet fragmentation. Longer is not safer either: an extended hard spin packs the pellet so tightly that resuspension turns violent, which defeats the purpose.

The honest footnote to that table: no scalp trial demonstrates that 5× beats 2.5×. If a single-spin system reliably measures 2–3× with clean handling, you are inside the range the published half-head trials worked in, and the burden of proof sits with anyone telling you to add complexity.

Leukocyte content is the other fraction decision. Including the buffy coat raises growth-factor and enzyme load together; excluding it gives a cleaner, lower-inflammation product. Scalp evidence does not settle the question — which is precisely why your protocol should. Pick leukocyte-rich or leukocyte-poor, state it, and stop letting the answer depend on who is pipetting that day.

Tubes, anticoagulant and kit systems#

ACD-A and 3.2% sodium citrate are the two defensible anticoagulants for reinjected product; both are dosed near 1:9 and both need immediate gentle inversion. EDTA belongs to the haematology analyser only. Gel-separator citrate tubes are convenient in single-spin workflows, with a known cost: a slice of the platelet yield stays at the gel interface, which is one reason measured concentration factors often undershoot expectations.

Closed commercial kits buy a sealed sterility path, consistent tube geometry and an audit trail, at roughly €40–150 per session against under €10 for open tubes. Neither choice is wrong; what is wrong is assuming the kit-box number describes your product. Insert claims are generated at ideal fill volumes with perfect technique, and real-world yields commonly land 30–50% below them. Record the lot number of whatever you use, and re-verify by counting whenever it changes. Training is the better half of the spend here — structured preparation modules exist across the industry, Bind Pharma runs one such programme — because their real value is forcing a team to write its numbers down and defend them.

Platelet concentration: targets and their limits#

Most scalp protocols aim for a platelet concentration of 2–6× the patient's baseline. The often-quoted absolute threshold of 1.0–1.5 million platelets per microlitre was imported from oral-maxillofacial and orthopaedic work decades ago; nothing on the scalp derives it independently. Treat it as a reference point, not a pass mark.

Here is the part most teams get backwards: the largest source of dose variation in a standardised clinic is not the spin — it is the patient. Normal baseline counts run from 150 to 450 ×10⁹/L, a three-fold spread, so an identical protocol delivers a three-fold range of platelet dose across a week's list. This is why dose, not factor alone, belongs in the record: concentration multiplied by injected volume, logged per session. Two patients "treated identically" may have received 3 billion and 9 billion platelets, and if that is never written down, no pattern in your outcomes will ever become visible.

Handling: the last thirty minutes#

Timing discipline is cheap and routinely ignored. Draw once the patient is confirmed in the chair, not during the consultation to save time. Process at room temperature, resuspend by gentle repeated inversion — never a vortex — and inject within roughly 60 minutes of the draw. Label the syringe with patient identity the moment it is filled; a strict single-patient workflow from draw to needle is the only reliable defence against the worst error this treatment can produce. The injection stage itself — depths, spacing, volumes per point — is covered in our step-by-step PRP protocol.

Verification: counts turn a document into a protocol#

A written protocol you never audit is a belief system. The audit is simple: baseline and product platelet counts on a benchtop analyser, with product divided by baseline as your concentration factor. Count every batch for the first month of a new programme, then drop to a monthly spot-check plus a forced recount after any change — new kit lot, centrifuge service, new operator. Expect the drift you find to be boring: fill volumes creeping, timers rounded down, a brake left on. Fix one variable at a time and recount, as you would tune any process.

This is also where prp standardisation meets the commercial argument. A clinic building PRP into a proper service line — pricing, capacity, retention, as laid out in our piece on building a PRP programme — is ultimately selling repeatability, and repeatability is a training outcome before it is an equipment outcome. Teams drilled on why each parameter exists, not just the sequence of button presses, are the ones whose product survives staff turnover; that case is made in our review of PRP training for clinic teams. Standardise first, measure always, and market only the numbers you can prove.

Sources and further reading#

• Gentile P, Garcovich S, Bielli A, et al. The effect of platelet-rich plasma in hair regrowth: a randomized placebo-controlled trial. Stem Cells Translational Medicine. 2015;4(11):1317–1323.
• Alves R, Grimalt R. Randomized placebo-controlled, double-blind, half-head study to assess the efficacy of platelet-rich plasma on the treatment of androgenetic alopecia. Dermatologic Surgery. 2016;42(4):491–497.