What are the types of platelet-rich plasma (PRP) orthobiologics?

Types of Platelet-Rich Plasma (PRP) Orthobiologics

Platelet-rich plasma (PRP) orthobiologics can be classified into four main types based on leukocyte content and red blood cell presence: PRP, Leukocyte-rich PRP (L-PRP), Platelet-rich fibrin (PRF), and Leukocyte-rich platelet-rich fibrin (L-PRF), with each having red blood cell-rich variants. 1

Primary Classification System

According to the International Society on Thrombosis and Haemostasis (ISTH) classification system, PRP products are categorized based on three key components:

1. Cellular Content:

   • PRP (without leukocytes, <1% of total cell count)
   • L-PRP (with leukocytes, ≥1% of total cell count)
   • PRF (fibrin-based without leukocytes)
   • L-PRF (fibrin-based with leukocytes)

2. Red Blood Cell Content:

   • Standard versions (minimal RBCs, <10% of total cell count)
   • Red-cell rich variants (≥10% of total cell count):
     • Red-PRP
     • Red-L-PRP
     • Red-PRF
     • Red-L-PRF

3. Activation Status:

   • Type I: No activation
   • Type II: With activation
   • Type III: Other activation methods 1

Additional Classification Parameters

The comprehensive classification also includes:

• Platelet Concentration:

  • Category A: Low concentration (<900,000 platelets/μL)
  • Category B: Medium concentration (900,000-1,700,000 platelets/μL)
  • Category C: High concentration (>1,700,000 platelets/μL) 1, 2

• Preparation Method:

  1. Gravitational centrifugation techniques
  2. Standard cell separators
  3. Autologous selective filtration technology (plateletpheresis) 1, 2

Clinical Relevance of Different PRP Types

The different PRP formulations have varying biological properties and potential clinical applications:

• Standard PRP: Contains minimal leukocytes and RBCs, providing concentrated growth factors with reduced inflammatory potential

• L-PRP: Contains leukocytes that contribute immune and antibacterial properties, but may increase inflammatory response

• PRF and L-PRF: Provide a fibrin scaffold that can act as a temporary matrix to assist tissue repair 1

• Red blood cell-rich variants: Contain significant RBC content, which may affect the biological activity of the preparation 1

Preparation Considerations

PRP preparation involves several critical steps:

• Blood collection: Typically using trisodium citrate as the anticoagulant (EDTA should be avoided as it damages platelets) 2

• Centrifugation: Low-g centrifugation for short periods maximizes platelet yield while maintaining viability 2

• Activation: May occur naturally upon contact with collagen-rich tissues or be induced prior to application 2

Clinical Applications

Different PRP formulations may be more suitable for specific orthopedic applications:

• For tendinopathies: Leukocyte-rich PRP (L-PRP) has shown efficacy, particularly for lateral epicondylitis 2, 3

• For osteoarthritis: Leukocyte-poor PRP (LP-PRP) is generally preferred 2, 3

• For patellar tendinopathy: L-PRP has demonstrated moderate evidence of efficacy 3

Limitations and Challenges

The field of PRP orthobiologics faces several challenges:

• Lack of standardization in preparation methods
• Variability in platelet concentration
• Differences in cellular content
• Variability in activation techniques
• Heterogeneity in application methods 2

These factors contribute to inconsistent clinical outcomes and make direct comparison between studies difficult.

Future Directions

For optimal use of PRP orthobiologics:

• Standardization of preparation protocols is essential
• Large-scale clinical trials with proper design are needed
• Better understanding of which PRP type is optimal for specific conditions is required 2

The classification system proposed by the ISTH provides a framework for standardized reporting and comparison of PRP preparations, which is crucial for advancing the field of orthobiologic therapy.