Platelet Pathogen Reduction Technology. Should We Stay or Should We Go…?

3. Advantages of PRT for Platelet Transfusions

A- Safety and efficiency benefits.

B- Evidence supporting advantages (extended shelf-life of platelets, decreased transfusion-transmitted infections, reduced risk of GVDH)

Overall Pathogen reduction technology (PRT) has several effects which seems to be mainly positive. We have summarized and commented on most of those here below:

i) 

PRT extends PLT shelf-life.

ii) 

PRT and transfusion reactions.

iii) 

PRT reduces Ta-GvHD.

iv) 

PRT and TTI.

v) 

PRT impact on coagulation proteins.

vi) 

PRT harmonizes TTI risk between countries.

vii) 

PRT does not affect the presence of pre-existing antibodies.

viii) 

PRT and sepsis

i) 

PRT extends PLT shelf-life

The lifespan of platelets (PLT) is currently limited to 5 days. Therefore, any tool that could extend the shelf life of PLT is highly desirable for any Blood Transfusion Service (BTS). The most widely adopted system for monitoring PLT contamination is BacT/ALERT®. This system is particularly prevalent in the UK and Ireland and helps monitor bacterial growth to prevent transfusion-transmitted infections (TTI). BacT/ALERT® can identify contaminated PLT units at a very early stage. Recent studies have shown that BacT/ALERT® can help extend PLT shelf life to 7 days [Ramirez-Arcos]. Additionally, the INTERCEPT® system has demonstrated the ability to preserve PLT quality over 7 days of storage [Ohlsson S]. The potential for extending PLT shelf life should be considered in any cost analysis of pathogen reduction technology (PRT) implementation. A Spanish study indicated that PRT can help reduce the rate of PLT outdates [Gorria C 2020].

ii) 

PRT reduces transfusion reactions.

PRT has been associated with a reduction of PLT transfusion reactions [Gathof 2010] [Pitman JP 2023]. The exact reason is unknown; however, this may simply be due to the inactivation of white blood cells and the consequent abrogation of cytokine production. Some authors have hypothesized a reduction of reactive stimuli by LPS, anti CD3+ and anti CD28 [Fast LD].

iii) 

PRT reduces Ta-GvHD

Irradiation of blood products is used to to prevent the development of Transfusion Associated Graft versus Host Disease (TA-GvHD). Indications for irradiated blood components include patients undergoing intrauterine transfusion, neonatal exchange transfusion, those with congenital cell-mediated immunodeficiencies, patients with Hodgkin lymphoma (for all transfusions during their lifetime), hematopoietic stem cell transplant recipients (both autologous and allogeneic), donors of allogeneic hematopoietic stem cells (in the week prior to and during stem cell harvest), CAR-T therapy recipients (7 days prior to collection and 3 months post-infusion), patients receiving purine analog therapy (e.g., fludarabine, cladribine, deoxycoformycin, bendamustine, clofarabine), those undergoing ATG or alemtuzumab therapy for hematologic diseases, recipients of donations from biologic relatives, and recipients of donations selected on the basis of HLA matching. Early reports in large cohorts of patients in France and Switzerland have shown that pathogen reduction technology (PRT) has strong efficacy for the prevention of TA-GvHD [Corash L 2016]. A study by Fast L and colleagues demonstraated that PRT is even more effective than irradiation for the inactivation of T cells [Castro 2018], as irradiation does not fully impair CD69 expression and the potential for lymphocyte proliferation [Fast LD].

Recently, Sim J and colleagues conducted a randomized prospective study to better evaluate the efficacy and safety of PRT. They studied a relatively large allogeneic transplant cohort (n=30) where blood products were treated only with PRT and did not undergo any leukoreduction or irradiation [Sim J 2019]. This study was successful, as none of the patients developed TA-GvHD. This finding is particularly relevant within hematology, highlighting the potential of PRT to make blood product irradiation and leukoreduction redundant. Additionally, from an economic perspective, this could significantly reduce costs [Fast L 2021]. Liebermann and colleagues also commented on the prevention of CMV infection through leukoreduction, noting that PRT can effectively replace leukoreduction for CMV prevention [Liebermann 2014].

iv) 

PRT reduces TTI

The capacity of reducing the risk of TTI varies according to PRT type. It also differs if PLT are resuspended in plasma or in platelet additive solutions (PAS). The published data on INTERCEPT® showed a high efficacy against: i) Protozoa (Plasmodium falciparum, Trypanosoma Cruzi, Leishmania Mexicana, Leishmania major Jish, Babesia microti); ii) Gram-Negative Bacteria (Escherichia coli, Serratia marcescens, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella choleraesuis, Yersinia enterocolitica, Enterobacter cloacae, Anaplasma phagocytophilum); iii) Gram-Positive Bacteria (Staphylococcus epidermis, Staphylococcus aureus, Streptococcus pyogenes, Listeria monocytogenes, Corynebacterium minutissimum, Bacillus cereus (vegetative), Bifidobacterium adolescentis, Propionibacterium acnes, Lactobacillus species, Clostridium perfringens (vegetative form), Spirochete Bacteria such as Treponema pallidum and Borrelia burgdorferi); iii) Enveloped viruses (HIV-1, HBV (strain MS-2), HCV (strain Hutchinson), HTLV-I , HTLV-II, CMV, Bovine Viral Diarrhea Virus, Duck Hepatitis B Virus, Pseudorabies virus, West Nile Virus, SARS-CoV2 , Chikungunya virus, Influenza A H5N1 virus (Avian Influenza, Zika, Dengue, Yellow Fever); iv) Non-Enveloped Viruses (Bluetongue Virus type 11, Calicivirus, Human Adenovirus-5, Parvovirus B19) [INTERCEPT Platelets, Technical Data Sheet] [Lanteri 2020 MC]. The technical data sheet available on MIRASOL® is not so informative, but clearly states that even this PRT is efficacious against enveloped and non-enveloped viruses, gram negative and gram-positive bacteria and parasites [https://www.terumobct.com/Public/306690232.pdf].

In the case of THERAFLEX activity against the following bacteria is reported (Enterobacter cloacae, Escherichia coli, Klebsiella Pneumoniae, Morganella morganii, Proteus mirabilis, Pseudomonas fluorescens, Serratia marcescens, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus bovis, Streptococcus dysgalactiae, Streptococcus pyogenes, Listeria monocytogenes, Acinetobacter baumannii, Streptococcus agalactiae, Streptococcus pneumoniae, Bacillus cereus, Bacillus thuringiensis, Propionibacterium acnes) [https://aob.amegroups.org/article/view/6833/html]. Also, activity against parasites sucha s Babesia divergens [Castro E 2014] and African mosquito-borne flaviviruses such as West Nile virus (WNV) and Usutu virus (USUV) have been shown [Graveman U 2024].

The use of PRT is quite promising. At the present they are several reports on the use of PRT. For example, Pitman reported on 1,221,031 platelet transfusions in France over 2010-2020 [Pitman 2023]. Escolar and colleagues reported that >875,000 transfusion treated with INTERCEPT® and > 700,000 treated with MIRASOL® have been administered so far, and no case of TTI or sepsis was reported [Escolar].

v) 

PRT impact on plasma coagulation proteins

Plasma products treated with PRT will have reduced levels of key coagulation proteins. Statistically significant reductions in FII, FV, FVIII, FIX, and FXI have been shown [Coene J 2014]. However, this may not necessarily impair the hemostatic function of the plasma product. For example, a thrombin generation (TG) study conducted on plasma treated with INTERCEPT® showed TG levels similar to those of untreated plasmaF, suggesting that hemostatic function is preserved [Ravanat 2018].

Studies have shown that solvent/detergent treated plasma and MB methylene blue) treated can affect Protein-S levels [Flamholz 2000] [Yarranton H] [Hellstern 2011]. This is relevant because Protein-S is a co-factor of Protein-C and is essential for its conversion into activated Protein-C (APC). APC balances the actions of FVa and FVIIIa [Piccin A et al 2022]. MB-treated plasma best preserves FV and FXI levels compared to INTERCEPT® [Backholer L 2016]. This information is particularly relevant because often platelets (PLT) are still resuspended in plasma [Larrea L].

4. Criticisms and Limitations of PRT

Highlight criticisms and limitations (Cost and organizational implications, storage lesion, impact on platelet quality and efficacy, alloimmunization, etc.). Evidence supporting concerns.

The following points were identified as criticism and limitation of PRT:

i) 

Bleeding risk

ii) 

PLT increment count

iii) 

Biochemical changes

iv) 

Mitochondrial DNA inactivation

v) 

PRT alters microRNA

vi) 

Pathogens not impacted by PRT

vii) 

Costs

i) 

Bleeding risk and PLT count increment

The possibility that PRT may affect platelet quality and contribute to a higher bleeding risk has been a concern for several investigators and continues to be so for some. An exhaustive Cochrane review on the risk of bleeding associated with PRT was carried out in 2017 [Estcourt LJ]. More recently, systematic review of all published randomized controlled trials was published by the Italian group of Pati I in 2022. In this study, Pati I and colleagues reported no difference in clinically significant bleeding with INTERCEPT® and MIRASOL®. However, a higher number of bleeding events was observed in the PRT groups [Pati I].

Among these studies, the most concerning is the one conducted by the Dutch group of Kerkhoffs JLH and colleagues [Kerkhoffs JLH 2010]. In this study, a reduced 1-hour corrected count increment (CCI) was documented using INTERCEPT®. Moreover, an increased risk of bleeding was also documented. Interestingly, patients with hematological malignancies such as AML, ALL, and LNH were included. This is relevant since these patients have very low PLT counts and are quite prone to bleeding.

Similarly, the Italian Platelet Technology Assessment Study (IPTAS) showed that the absolute risk difference in WHO Grade ≥2 bleeding for INTERCEPT® was 6.1% (with an upper one-sided 97.5% confidence limit of 19.2%), while the absolute risk difference for MIRASOL® was better at 4.1% (with an upper one-sided 97.5% confidence limit of 18.4%) [Rebulla 2017]. However, in neither case was the absolute risk difference statistically significant. In both trials, post-transfusion platelet count increments were significantly lower in treated versus control patients [Rebulla 2017].

A randomized French study (EFFIPAP) did not show that PLTs treated with PRT (INTERCEPT®) and resuspended in PAS were associated with any higher rate of WHO Grade ≥2 bleeding. However, a 12.5% difference margin was considered for this non-inferiority study [Garban F].

Osselaer JC and colleagues studied a large cohort of patients (n = 651) treated with 5106 blood components transfused with PRT INTERCEPT® products. The authors reported no changes in the number of PLT doses administered with and without PRT implementation [Osselaer JC]. Cazenave JP and colleagues also reported similar findings. Interestingly, these authors also found a reduced number of transfusion reactions associated with PRT using INTERCEPT®. More recently, an Austrian study reported a similar consumption of blood products before and after PRT implementation (INTERCEPT®) over 21 months of follow-up. A similar finding was also reported by Infanti L and colleagues, in a study that also showed the possibility of extending PLT shelf life to 7 days [Infanti L].

This suggests that no significant increase in bleeding was seen with PRT implementation [Amato 2017]. The same group of authors also studied a large cohort of patients treated with massive transfusion [Nussbaumer]. Interestingly, no increased bleeding risk was seen after PRT implementation. Additionally, both the SPRINT [McCullough J] and the EFFIPAP [Garban F] studies enrolled patients with severe hematological conditions and low PLT counts, suggesting that these “fragile” patients are not adversely affected when PRT is implemented.

ii) 

PLT increment count

Several reports have suggested that PRT treated PLT lead to an inferior post transfusion PLT count compared to this obtained when PLT without any PRT treatment are transfused [Blake T 2021]. To analyze this aspect, the concept of corrected count increment (CCI) has been introduced. CCI was initially developed with the intent to facilitate physicians dealing with differential diagnosis of idiopathic thrombocytopenic purpura (ITP) and is currently used for analyzing platelet refractoriness. This index directly correlates to the PLT dose transfused. CCI is based on a small calculation on PLT numbers based on a post-transfusion specimen collected 1 hour after transfusion (CCI_1hour). This index also considers the patient’s body surface area (BSA). Usually after a transfusion of a standard unit of PLT in a patient with not-active bleeding, the PLT count shows an increment between 5-10.000/µL.

If the CCI does not show an increment, further investigations would be required to identify the cause (e.g., immunization to HLA or HPA antigens, ITP, sepsis, etc). A Canadian simulation study reported on possible risk of wastages and PLT shortages caused by PRT implementation. The authors described a reduced CCI when INTERCEPT® was used. This would have led to prescribing more products, and enhanced patient’s exposure to more blood donors. The authors concluded that this would impact on supply chain and potentially increase the risk of TTI because larger exposure to blood products [Blake T 2021]. Different results were shown by the SPRINT randomized study. In particular, CCI at 1 hour and at 24 hours post transfusion were lower for patients transfused with PRT treated PLT. Also, the transfusion interval was shorter leading overall to a higher prescription of PLT, however, no differences in clinical bleeding were seen [Murphy S et al 2006]. However, other studies have not confirmed this data and have not reported any increased PLT consumption for INTERCEPT® [Cazenave][Osselaer][Amato][Nussbaumer][Infanti].

iii) 

Biochemical changes

Malvaux N et al. reported on changes in biochemical markers in PLT concentrate treated with either MIRASOL® or INTERCEPT®. A higher production of lactate, along with a greater reduction in glucose, was observed for MIRASOL®. Swirling at day 5 was also worse when PLT were treated with MIRASOL®, suggesting that INTERCEPT® should be preferred [Malvaux 2022]. Conversely, PLT treated with INTERCEPT® preserved swirling until day 7 [Malvaux 2022] [Lotens Transfusion 2018] [Ohlsson Vox Sang 2018]. However, some biochemical studies have shown problems even when INTERCEPT® is used. Specifically, Stivala S and colleagues reported that PLT treated with INTERCEPT® exhibited reduced function in response to activation agonists (i.e., collagen, thrombin, and von Willebrand Factor). The same study showed increased PLT apoptosis through Bak upregulation and a caspase-dependent pathway, enhancing PLT clearance from the circulation, with obvious clinical implications [Stivala S].

iv) 

Mitochondrial DNA inactivation

Following ultraviolet (UV) light-based pathogen inactivation, mitochondrial DNA (mitDNA) damage can occur. Specific PCR multiplex assays have been developed for testing mitDNA. These assays have demonstrated that pathogen reduction technology is responsible for this damage [Kim S][Bruchmüller]. Furthermore, Bakkour and colleagues showed that mitDNA damage is primarily UV-dependent and not related to the presence of amotosalen [Bakkour].

iv) PRT alters microRNA

Diallo I and his colleagues were the first to report alterations in microRNAs contained in platelet-derived microparticles (PMP) [Diallo I]. The authors suggested that pathogen reduction technology might influence microRNA loading into PMP, which may indirectly affect PMP bioactivity. Alterations of microRNAs (miRNAs) stored within PMP were observed with INTERCEPT®. No such alterations were seen with MIRASOL®. The authors attributed these alterations to the presence of the additive storage solution (amotosalen) used with INTERCEPT®. Arnason and colleagues reported that INTERCEPT® affects only the expression of miRNA-96-5p, showing downregulation of this particular miRNA out of the 25 miRNAs analyzed [Arnason].

v) 

pathogens not impacted by PRT

PRT can significantly contribute to reducing the pathogen load associated with transfusion, but no type of PRT ensures full sterility of blood products. Additionally, PRT is clearly ineffective against prions, spores, and some viruses without a lipid envelope (e.g., Hepatitis A). However, MIRASOL® and THERAFLEX® have been shown to inhibit HEV [Owada 2017]

vi) 

PRT high costs

The cost analysis of implementing Pathogen Reduction Technology varies between studies and in different geographical, epidemiological and economical settings. Several factors affect this cost, including the type of PRT procedure, shorter intervals of sustained transfusion, extended shelf-life from 5 to 7 days, the elimination of test procedures ( such as CMV testing and bacterial culture), the elimination of gamma irradiation.

Cicchetti A and colleagues conducted a cost analysis on PRT in Italian patients, considering over 50,000 transfused patients in one year. They predicted an overall cost increase of 30% [Cicchetti A 2018]. Additionally, the same authors suggested that while PRT can significantly reduce the risk of transfusion-transmitted infections (TTI), it does not guarantee protection against all TTIs. Furthermore, they indicated that PRT is not applicable to all blood products (e.g., red cells) and may cause alterations in product quality [Cicchetti A 2018].

In a constructive criticism, Farrugia emphasized that although current PRT is not perfect, previous regulatory authorities, such as the US Blood Product Advisory Committee, investigating blood inquiries related to HIV transmission, have clearly stated that “partial solutions should be welcome and where possible implemented by BTS” [Blood Products Advisory]. We concur with this statement. Our perspective is that ensuring and improving patient safety should always remain a priority for any BTS.

CF Bell and colleagues, in an earlier cost analysis, also noted that introducing PRT would render bacterial testing redundant, leading to indirect cost savings [Bell CF 2003]. The cost saving associated to the prevention of a potentially emerging virus is very significant when considered in economic studies.

Most study on cost analysis have been conducted on INTERCEPT only. In this respect, a study sponsored by INTERCEPT showed that by adopting PRT the incremental cost ratio (ICERs) of PLT is certainly higher, however this may be justified if new emergent pathogens may arise with a 10-fold risk of transmission with transfusion [Davison N et al 2021]. Gregoire Y and colleagues from Québec showed an incremental cost effectiveness ratio (ICER) on quality-adjusted life years (QALY) equal to $8.1 million/QALY [Gregoire Y]. However, in the presence of a new blood-borne pathogen the ICER was reduced to $123,063. Rosskopf K and his colleagues reported on the advantages of not having gamma irradiation and bacterial screening in place. The analysis concluded that implementing PRT added an additional cost of +7.5% [Rosskopf K]. Mc Cullough and colleagues reported on significant cost saving for each PLT unit treated with PRT, if standard microbiological testing would be removed. Furthermore, the same authors stressed that a shelf-life extension to 7 days would contribute significantly to cost reduction [Mc Cullough 2015].

6. Future Perspectives

• A. Potential improvements and advancements in PRT

The prevention of TTI, cannot prescind from implementing PRT or similar systems for RCC and plasma products. Recently a randomized trial called ReCePI on INTERCEPT for RCC has been conducted in patients undergoing cardiovascular surgery. The trial demonstrated non-inferiority for INTERCEPT treated RCC compared to conventional RCC as measured by the incidence of acute kidney injury (AKI).

Similarly study on fibrinogen compound like cryoprecipitate are currently undergoing [Keltner NA Transfusion 2024].

7. Should We Stay or Should We Go?

• A. Analysis of arguments for and against PRT

A critical review of previous RCT studies did not identify relevant clinical complications when PRT was implemented. For example, the worrisome higher bleeding (>WHO grade 2) or lower CCI did not really emerged, even if data have shown that PRT may impact on the post transfusion PLT count. From the perspective of improving blood safety, there is no clear reason why PRT should not be further implemented. The economic cost associated with PRT implementation, may have been an obvious obstacle. However, considering the benefits of PRT (reduced risk of TTI, better TA-GvHD prevention and no need of irradiation), it is not clear to these authors why PRT has not been widely adopted. Perhaps, the large number of RCT designed to prove that PRT does not impact on product quality (reduced CCI count, or increased bleedings), may have contributed to create he perception that PRT is unsafe. Interestingly, those centers that have already adopted PRT have not moved away from this practice. This indirectly validates PRT. However, the wait and watch approach adopted by other BTS indicates that a large resistance towards implementing PRT still exists.

8. Conclusions

A. Summary of Key Points

B. Personal Recommendation and Final Remarks

TTI in Transfusion Medicine have always been a challenge, particularly because new emerging disease will always be present even in the future. The recent COVID-19 pandemic is a good example of this. For this reason, PRT in transfusion Medicine offers the possibility to reduce and control future events caused by unknown pathogens. The relationship between zoonosis and TTI (West Nile Virus, Zika, MERS, SARS, Malaria, Chikungunya virus etc.) is large and well reported in the literature. The possibility to implement blood safety by using UV lights with or without intercalating agents able to block DNA and RNA replication signaling, is likely to become a cornerstone of Transfusion Medicine. Moreover, the introduction of this technology will even potentiate safety of existing PCR screening practice, ensuring that any false negative sample potentially infective, will still undergo inactivation. This transfusion concept has also been recently debated by Farrugia in his description of a “safety tripod” made by 1) appropriate donor selection, 2) blood screening with molecular technology and 3) the adoption of viral inactivation processes [Farrugia A 2023].

Another advantage of introducing PRT, could be the extended shelf life of blood products such as PLTs. This will have an economical and inventory management practical benefit, allowing to have more products available for longer period of time. Implementation of PRT in low-income countries (e.g. sub-Saharan Africa countries), where TTI risk is high, in theory could be beneficial. For example, in Ghana the risk of blood parasitemia by malaria is >50% [Kasirye R].

However this is not practicable and moreover unrealistic due to the high cost [Allain JP 2016]. Paradoxically, PRT implementation seems more difficult to be accepted in Western countries. Part of the difficulty consist in cultural resistance and lack of vision. Several transfusionists and clinician are also reluctant to implement these devices because afraid of side effects or inefficacy of PRT. This is particularly true in UK and Ireland, where any new procedure affecting the blood products is a delicate and sensitive topic or better to say as a “mine field”. This is probably an indirect psychological consequence of the infected blood products (with HIV and hepatitis) scandals and the still ongoing “Blood Inquiry”. Furthermore, cost analysis is often carried out by local BTS, and local services are discouraged to consider PRT because excessive costs. Therefore, we believe that national health regulatory authorities and international societies (above local BTS), should be involved in accurately evaluating scientific data to clarify the role if PRT implementation is really needed or not.