Human T-lymphotropic virus in Irish blood donors: Impact on future testing strategy

Abstract

Aim: A risk-based approach to the testing of blood donations for Human T-Lymphotropic Virus (HTLV) should include an assessment of blood donation seroepidemiology. The objectives of the present study were to determine the proportion of HTLV positive units in Irish blood donations, and subsequently, to estimate the current risk of transfusion transmitted HTLV (TT-HTLV).

Methods: Over 3 million donations screened between 1996 and 2020, were included in the study (n = 3,666,253). Factors considered in the assessment of TT-HTLV risk included: (I) HTLV seropositivity, (ii) probability of a leucodepletion failure, and (iii) the HTLV testing strategy.

Results: Six HTLV positive donations were detected throughout the study period, all of them in previously unscreened blood donors (0.000164%; n = 6/3,666,253), 3 of whom had donated prior to the introduction of HLTV antibody testing. On average 0.11% of manufactured blood components assessed, failed to satisfy the leucodepletion quality assurance criteria of less than 1 × 10⁶ cells/unit. In using these values to model the risk of TT-HTLV, it was shown that the combination of leucodepletion with either universal screening of all = donors, or selective testing of first-time donors, a possible HTLV transfusion transmitted infection would be prevented every 468-3776 years.

Conclusions: This is the first report on the proportion of HTLV positive in Irish blood donations (1996-2020) and will be used to inform blood donation screening policy in Ireland. Evidence is provided for recommending a selective HTLV donor screening algorithm in Ireland that is accompanied by a robust framework for continued surveillance of leucodepletion failure rate.

Keywords: HTLV; Ireland; blood; donation; epidemiology; human T-Lymphotropic virus; risk; seropositivity.

FIGURE 1

Prevented HTLV transfusion transmitted infections between 1996 and 2020 according to each testing algorithm. (A) The estimated number of prevented transfusion‐transmitted HTLV infections (TT‐HTLV) per number of donations screened per year is shown. A universal testing algorithm is depicted by filled shapes and varied depending on leucodepletion parameters. A selective first‐time donor testing algorithm is depicted by striped shapes and varied depending on leucodepletion parameters. The circled values estimate the number of prevented TT‐HLTV using selective first‐time donor HTLV screening in combination with leucodepletion. (B) The estimated number of prevented transfusion‐transmitted HTLV infections (TT‐HTLV) compared to leucodepletion without any HTLV testing is shown. The prevented TT‐HTLV for first‐time testing, universal testing and per HTLV strain shown. Leucodepletion is the most significant factor at reducing TT‐HTLV. Rates are based on quality control data from 2018 to 2020.