What is plasma rich platelet (PRP) therapy?

Basics of Platelet-Rich Plasma (PRP) Therapy

Platelet-rich plasma (PRP) therapy is an autologous blood-derived product containing concentrated platelets that release growth factors and cytokines to potentially promote tissue healing, though its clinical efficacy remains uncertain for most applications due to lack of standardization and inconsistent evidence. 1

Definition and Preparation

PRP is defined as an autologous derivative of whole blood that contains a supraphysiological concentration of platelets, typically at least 2-3 times above normal circulating levels 1, 2. The preparation process involves:

1. Collection of the patient's blood with appropriate anticoagulation

   • Trisodium citrate is most commonly used
   • Acid citrate dextrose (ACD) and citrate phosphate dextrose (CPD) are also effective
   • EDTA is not recommended as it causes platelet swelling and activation 1

2. Processing methods:

   • Gravitational centrifugation techniques (most common)
   • Standard cell separators
   • Autologous selective filtration technology (plateletpheresis) 1

3. Activation (optional):

   • PRP can be applied with or without activation
   • Activation triggers release of growth factors from platelet α-granules 1

Biological Mechanism

PRP's regenerative properties are based on:

• Release of bioactive proteins, growth factors, and cytokines upon platelet activation

• Creation of a local environment that promotes:

  • Angiogenesis
  • Stem cell homing
  • Cell migration and proliferation
  • Tissue differentiation
  • Deposition of matrix proteins like collagen 1, 3

• Development of a fibrin scaffold that acts as a temporary matrix to assist tissue repair 1

Classification System

The International Society on Thrombosis and Haemostasis has proposed a standardized classification system for PRP based on:

1. Presence of leukocytes (≥1%)
2. Presence of red blood cells (≥10%)
3. Activation method
4. Platelet concentration
5. Preparation technique 1

Main categories include:

• PRP (pure platelet-rich plasma)
• L-PRP (leukocyte-rich PRP)
• Red-PRP (red blood cell-rich PRP)
• Red-L-PRP (red blood cell and leukocyte-rich PRP)
• PRF (platelet-rich fibrin) variants 1

Clinical Applications

PRP has been investigated for various conditions with varying levels of evidence:

• Appropriate applications with moderate evidence:

  • General wound healing 1
  • Certain tendon pathologies (lateral epicondylitis, rotator cuff tendinopathy) 4
  • Patella tendinopathy 4

• Uncertain applications with limited evidence:

  • Burn injuries
  • Tendon injuries (general)
  • Acute muscle injuries
  • Bone healing
  • Maxillofacial injuries
  • Sports injuries
  • Osteoarthritis 1, 5

• Not recommended based on current guidelines:

  • Osteoarthritis treatment (The American College of Rheumatology/Arthritis Foundation strongly recommends against PRP for osteoarthritis) 5
  • Skin aging as beauty therapy 1

Limitations and Concerns

1. Lack of standardization:

   • Significant variability in preparation methods
   • Different platelet concentrations
   • Variable presence of leukocytes and red blood cells
   • Different activation protocols 1, 5

2. Inconsistent evidence:

   • Varying efficacy reported across studies
   • Many studies have moderate to high risk of bias
   • Poor patient stratification
   • Lack of standardized outcome measures 5

3. Quality control issues:

   • Need for proper characterization of PRP products
   • Importance of reporting:
     • Platelet yield
     • Purity (contamination with RBCs and WBCs)
     • Activation status
     • Growth factor content
     • Activation procedure 1

Safety Profile

PRP is generally considered safe as it uses the patient's own blood products, with no serious adverse effects consistently reported in studies 5, 6. However, its efficacy for improving morbidity, mortality, or quality of life remains unproven for most applications 5.

Key Considerations for Clinical Use

If considering PRP despite limited evidence:

1. Ensure proper characterization of the PRP product
2. Consider biorepository banking of samples for quality control
3. Use standardized outcome measures to assess response
4. Recognize that any benefits may be temporary
5. Consider PRP as an option primarily for chronic musculoskeletal conditions that have failed other established treatments 5, 4