One of the great things about social media (blogs, Twitter, etc.) is that it encourages dynamic dialogue and discussion. Academics and practitioners alike benefit from the new insights and ‘food for thought’ this generates. With this tenet in mind, here is a letter from Robert-Jan de Vos, Johann Windt and Adam Weir in response to the BJSM blog: Should we really abandon PRP in the treatment of lateral epicondylar tendinopathy? that was written in response to de Vos, Windt and Weir’s publication:  Strong evidence against platelet-rich plasma injections for chronic lateral epicondylar tendinopathy: a systematic review. Br J Sports Med. 2014;48(12):952-956. …comprende? We hope so. 

LETTER TO THE EDITOR BY DE VOS, WINDT, AND WEIR

With great interest we read the letter to the editor regarding our systematic review on the use of Platelet-rich Plasma (PRP) injections in patients with chronic lateral epicondylar tendinopathy.¹ We compliment the authors on their efforts to improve scientific quality in this field. The BJSM Blog is a fantastic forum to host discussions like this and we would encourage other readers to share their thoughts as well. There is a lot of common ground between the two groups but we were surprised that our systematic review conclusions were described as being ‘not properly supported by recent literature’. We would like to emphasise that it was properly designed and performed according to the PRISMA guidelines. In response to this criticism we address some aspects of the letter and explain why we think our systematic review is of value in the field of tendinopathy.

Diagnostic terminology

We hope that we are on the same page regarding the diagnosis. The authors use a different terminology and refer to ‘chronic lateral epicondylitis’. We know that inflammatory theories in tendinopathy are currently popular, but the generally accepted term is “tendinopathy” for these conditions.² This might sound as a semantic discussion, but if authors in a research field cannot agree on terminology and diagnostic criteria for a certain condition, it will be very hard to make comparisons in scientific literature.

Meta analysis

While meta analysis is generally accepted to be the highest level of evidence you should always consider if it is correct to use this technique. By presenting a meta-analysis in the way the authors have done, study design labels (e.g. RCTs or CCTs) are used to imply high study quality and low risk of bias. The assessment of risk of bias is a key step in conducting systematic review and possible meta analysis. It plays an important role in the final assessment of the strength of the evidence. The first question we should ask is whether the included studies have a low risk of bias. If not, it is questionable if the outcome really reflects the efficacy of PRP or the effect of studies with a high risk of bias. We feel that to present a meta analysis one must also first assess the risk of bias and argue the case as to why it is valid to perform a meta analysis. It is known that lower study methodological quality is associated with better treatment outcomes in patellar tendinopathy.³ To simply pool the outcomes of all RCTs performed in this field does therefore not automatically imply a ‘highest level of evidence’.

Corticosteroids

We fully agree with the authors that corticosteroid injections should not be used for control groups in PRP studies. We support the approach to leave these studies out of the final evaluation because of the detrimental effect of corticosteroids.⁴ Corticosteroid injections should be discouraged in the routine management of tendinopathy and they are not suitable as a control group because of the detrimental long-term effects.

Placebo as control

The authors present their analysis of PRP vs autologous blood injections. We would stress the need for more placebo-controlled RCTs, rather than comparison to another active treatment. Creaney et al. randomised patients to a PRP or autologous blood injection and found no significant differences in outcome.⁵ They then concluded that both autologous blood and PRP injections are useful second-line therapies to improve clinical outcomes. However, it would only be possible to draw this conclusion if a placebo-arm was used in the study. Comparison with autologous blood injections would only make sense if this would was “usual care” for tendinopathies. A previous systematic review showed that there was strong evidence that autologous blood injections are not efficacious⁶, so the use of autologous blood injections in routine care or as a control group cannot not be advised.

Should we abandon PRP?

In our opinion the authors do not present a case for the use of PRP in clinical practice. They provide us with a meta analysis where no difference is found between PRP and autologous blood injections.

We feel that at the current time there is strong evidence that both PRP and autologous blood injections are not efficacious. The fact that autologous blood is cheaper than PRP cannot be used to argue a case for it being preferred. In our clinical practice we prefer to use neither.

We are aware that the conclusion of our systematic review is not popular,⁷ as attention for PRP treatment is still growing. We still feel that our review conclusion is robust and it is also supported by other high-quality placebo-controlled studies in the field of musculoskeletal medicine.^8-10 To end again on a positive note we agree with the authors’ final comment, where they advise for more placebo-controlled studies.

References

1. de Vos RJ, Windt J, Weir A. Strong evidence against platelet-rich plasma injections for chronic lateral epicondylar tendinopathy: a systematic review. Br J Sports Med 2014;48(12):952-6.
2. Khan KM, Cook JL, Kannus P, Maffulli N, Bonar SF. Time to abandon the “tendinitis” myth. BMJ 2002;324(7338):626-7.
3. Coleman BD, Khan KM, Maffulli N, Cook JL, Wark JD. Studies of surgical outcome after patellar tendinopathy: clinical significance of methodological deficiencies and guidelines for future studies. Victorian Institute of Sport Tendon Study Group. Scand J Med Sci Sports 2000;10(1):2-11.
4. Coombes BK, Bisset L, Vicenzino B. Efficacy and safety of corticosteroid injections and other injections for management of tendinopathy: a systematic review of randomised controlled trials. Lancet 2010;376(9754):1751-67.
5. Creaney L, Wallace A, Curtis M, Connell D. Growth factor-based therapies provide additional benefit beyond physical therapy in resistant elbow tendinopathy: a prospective, single-blind, randomised trial of autologous blood injections versus platelet-rich plasma injections. Br J Sports Med 2011;45(12):966-71.
6. de Vos RJ, van Veldhoven PL, Moen MH, Weir A, Tol JL, Maffulli N. Autologous growth factor injections in chronic tendinopathy: a systematic review. Br Med Bull 2010;95:63-77.
7. Gosens T, Mishra AK. Editorial in response to the systematic review by de Vos et al: ‘Strong evidence against platelet-rich plasma injections for chronic lateral epicondylar tendinopathy: a systematic review’. Br J Sports Med 2014;48(12):945-6.
8. de Vos RJ, Weir A, van Schie HT, Bierma-Zeinstra SM, Verhaar JA, Weinans H, et al. Platelet-rich plasma injection for chronic Achilles tendinopathy: a randomized controlled trial. JAMA 2010;303(2):144-9.
9. Reurink G, Goudswaard GJ, Moen MH, Weir A, Verhaar JA, Bierma-Zeinstra SM, et al. Platelet-rich plasma injections in acute muscle injury. N Engl J Med 2014;370(26):2546-7.
10. Schepull T, Kvist J, Norrman H, Trinks M, Berlin G, Aspenberg P. Autologous platelets have no effect on the healing of human achilles tendon ruptures: a randomized single-blind study. Am J Sports Med 2011;39(1):38-47.