(1) Safeguarding platelet donors: the value of bacterial screening, (2) Are whole blood donors with genetic haemochromatosis (GH) in England more likely to have infection risks?

1. Safeguarding platelet donors: the value of bacterial screening (International Society of Blood Transfusion, ISBT – Poster 148)

Background

Bacterial screening of platelets was introduced in England by NHS Blood and Transplant in 2011. Since then, 3.5 million platelets have been screened by NHSBT. In the last two years (2022-2023), we screened 536889 platelet donations with 286514 manufactured as pooled platelet donations. Donors of donations culture positive for significant bacteria were followed up to exclude underlying disease.

Aims

Here we describe the impact of bacterial screening on both blood safety but also as a potential early indicator of underlying illness in donors. We highlight the challenges of following up donors where a pooled platelet is contaminated with a potentially significant marker organism, and the importance of referral of such cases for investigation.

Methods

Bacterial screening is carried out using the large volume culture methods. In brief, pooled platelets are manufactured from 4 blood donations and held at 22⁰C for 36 hours. An 8 ml sample is cultured both aerobically and anaerobically on the BacT/Alert 3D analyser for 6 hours, released as negative to date, and recalled if initial reactive within 7 days. Initial reactive bottles are cultured for growth and identification. Where growth is confirmed in both the initial reactive bottles and pack, the results are issued as confirmed positive. If potentially significant organisms are identified, donors are contacted and asked to participate in a post-donation interview and as appropriate, referred for further investigations.

Results

Of the pooled platelets screened, 0.31% (873) were initially reactive at screening with 0.10% (294) confirmed positive. To date, we have reviewed the source of organisms isolated from bacterial screening of all pooled platelets in England in 2022 and 2023 (Table 1).

Most bacteria isolated from pooled platelet donations are skin commensals predominantly Cutibacterium acnes, small numbers of other bacteria usually found in the gut or oropharynx require investigation. In all confirmed cases no donors had disclosed any recent or current illness or ongoing medical investigations.

During 2022, a pooled platelet donation tested positive for Streptococcus gallolyticus subsp. pasteurianus, formerly S. bovis biotype II. All donors were asymptomatic at the time of donation and on follow up, associated red cells were negative on screening. All donors and their primary care physicians were contacted regarding the screening results. One donor had previously had a colonoscopy and the oldest donor, aged 75+, had a history of low Hb leading to deferral. Further discussion took place with the older donor in the pool given our previous experience of the increased risk of underlying disease in otherwise apparently healthy donors. Some 10 months later, following referral to gastroenterology and numerous investigations, an early diagnosis of colorectal cancer was reported resulting in bowel resection. Timely surgery led to cancer remission.

Summary/ Conclusion

Determining risk is challenging in asymptomatic individuals who are apparently healthy blood donors. The implementation of bacterial screening for platelets has not only improved transfusion safety but also led to early detection of underlying diseases in asymptomatic donors.

This screening process ensures early detection, donor follow-up, and specialist referrals, demonstrating its importance in both transfusion safety and donor health.

2. Are whole blood donors with genetic haemochromatosis (GH) in England more likely to have infection risks? (British Blood Transfusion Society, BBTS)

Introduction

GH is an inherited disorder which can cause severe complications and lead to death. Venesection, the primary treatment for GH, reduces morbidity and mortality. NHSBT allows GH patients on maintenance phase to donate whole blood if they meet the usual eligibility criteria. Over the past two years, we have noted donors with GH testing positive for markers of infection. To better understand the significance of this and identify areas for improvement, we assessed GH donor eligibility related to infection between November 2022 and November 2024.

Methods

We reviewed all registered GH donors to identify active donors and donors deferred for confirmed positive markers of infection. Positivity rates were compared to the whole blood donor (WBD) population in England.

Post-test discussion (PTD) notes and donation safety check forms for confirmed positive GH donors were reviewed to determine donor eligibility.

Results

A total of 2478 GH donors were registered during this period. 53.15% (1326/2478) were active donors, of which 0.45% (6/1326) were later permanently withdrawn due to syphilis (4/6) or anti-HBc (2/6) detection.

Of the four donors positive for syphilis infection, three were eligible; two were unaware of their past syphilis infection and one was treated for yaws. One donor was ineligible because they did not declare previous syphilis treatment.

A PTD is not carried out for donors with anti-HBc only therefore eligibility was not determined for these two donors.

WBD data for 2023 was obtained from routine surveillance. The positivity rate for syphilis in GH donors was 0.30% (4/1326, 95% CI 0.08-0.77%), compared to 0.06% (79/ 124,070, 95% CI 0.05-0.08%) in first-time WBDs.

The positivity rate for anti-HBc in GH donors was 0.15% (2/1326, 95% CI 0.02-0.54%) compared to estimated 0.73% (905/124,070, 95% CI 0.68-0.78%) in first-time WBDs.

Conclusion

The syphilis positivity rate in GH donors appears to be higher than in whole blood donors but numbers are low. Expanding our data analysis over a 5-year period will enable us to improve the significance of our findings. Prior screening of GH donors before donating will ensure GH patients can receive the venesection treatment they require and in the appropriate setting.

Outputs

1. (2025), Abstract. Vox Sanguinis, 120: 211. https://doi.org/10.1111/vox.70030
2. Abstract to be published in Transfusion Medicine – Official journal of BBTS