Leukocyte rich or leukocyte poor: two different products sold under one name

Ask any two clinics what PRP costs and you will get two numbers you can compare. Ask what is in it and the conversation usually ends at the same three sentences: we draw your blood, we spin it, we inject the concentrated platelets. That description is accurate and it conceals the single largest source of variation in the entire field.

Platelet rich plasma is not a drug. It is a category of preparation, and the preparations inside that category differ in platelet concentration, in volume, in whether they are activated before injection, and above all in whether the white blood cells were kept or discarded. That last choice splits PRP into two products with different biological behavior, and both are sold under the same three letters at the same price point.

The original element in this piece is a four question consultation script that forces the actual preparation parameters into the open before you pay, together with a reading of what each kind of non answer tells you about the clinic. The parameters exist on the device manufacturer's own specification sheet and take a clinic thirty seconds to look up. The reason patients almost never see them is that nobody asks in terms the clinic can answer, and the questions below are written to be answerable.

What the distinction actually is. Whole blood is separated by centrifugation into layers. Platelets concentrate in a narrow band near the boundary between plasma and red cells, and white blood cells, particularly neutrophils, concentrate in the same neighborhood. How aggressively the operator draws from that band, and how many spins the protocol uses, determines whether the final product is leukocyte rich, meaning white cell concentration above whole blood baseline, or leukocyte poor, meaning below it. The overview of how PRP is made covers the mechanics. What it cannot tell you is which side of that line any given clinic lands on, because the answer is a function of the specific system on the counter.

Leukocytes are not inert passengers. Neutrophils bring proteases and reactive oxygen species along with growth factors. In a degenerating tendon, that additional inflammatory signal is argued to be part of the point, because tendinopathy is characterized by a failed rather than excessive healing response and the tissue may need provoking. Inside a synovial joint, the same signal is argued to be a liability, because the joint lining reacts to it and short term pain flares are more commonly reported. The review of the leukocyte rich versus leukocyte poor debate lays out both positions and, importantly, does not declare a winner.

Where the evidence currently sits. For knee osteoarthritis, the head to head question has been examined directly. A systematic review of leukocyte rich versus leukocyte poor PRP for osteoarthritis is the most direct look at whether the distinction changes outcomes, and the broader comparison of PRP against hyaluronic acid in knee osteoarthritis is the study most often cited to justify offering PRP for joints at all. Read together, they support a defensible position rather than a settled one: PRP outperforms hyaluronic acid in pooled analyses, and the leukocyte question is not resolved with the confidence that clinical marketing implies in either direction. For tendon work, the leukocyte rich preparations are the ones with the larger share of positive trials, which is a different statement from saying they have been proven superior.

Question one: which system do you use, by name? Every commercial kit has a name. The answer should be a product name, not a description. A clinic that separates blood using a generic laboratory centrifuge and manual pipetting is not automatically worse, but it is operating without a standardized protocol, which means the product varies between operators and between visits.

Question two: is it a single spin or a double spin protocol? Single spin protocols generally yield lower platelet concentration and, depending on draw technique, often retain leukocytes. Double spin protocols concentrate platelets further and allow the leukocyte layer to be excluded more deliberately. Either answer is fine. No answer is the signal.

Question three: what platelet concentration does it produce relative to my baseline, and is it leukocyte rich or leukocyte poor? This is the question. It has a number attached and the number is on the manufacturer specification. Concentrations across commercial systems commonly range from roughly two times baseline to well above five times, which is a wide enough spread that two clinics quoting the same price are not selling the same thing.

Question four: why that one for my problem? This is where you find out whether the choice was made or inherited. A good answer connects the preparation to the tissue: leukocyte rich for a chronic tendon, leukocyte poor for an intraarticular injection, with a reason. A weak answer is that this is what the clinic has always used. That is not disqualifying, since most clinics own one system, but it should reframe the conversation from what is best for you to what is available here.

Reading the non answers. A clinic that cannot name the system is not tracking its own inputs. A clinic that says all PRP is essentially the same is stating something the published literature spent fifteen years disproving. A clinic that answers all four without hesitating has probably had the conversation before, which is itself the most useful data point you will collect, and it belongs alongside the other criteria for choosing a provider.

What the studies do not tell you. The largest weakness in this entire literature is that a majority of published PRP trials do not characterize the injected product at all. They report the system used, sometimes, and the volume, sometimes, and frequently neither the platelet concentration achieved nor the leukocyte content. That means when two trials of PRP for the same condition disagree, it is often impossible to know whether they disagreed about the treatment or simply administered two different treatments. Reporting standards have been proposed repeatedly and adopted inconsistently. Until that changes, pooled analyses in this field are averaging across products, and any confident claim that PRP does or does not work for a given joint is making a stronger statement than the underlying data supports.

The takeaway is not that one preparation is right. It is that you are buying a specified product and are usually being sold an unspecified one, and four questions at the consultation converts the first into the second.