Should all hematopoietic stem cell transplantation (HSCT) donors be routinely screened for human T-lymphotropic virus (HTLV) infection?

HTLV Screening for HSCT Donors

Routine universal HTLV screening is NOT recommended for all HSCT donors in low-prevalence areas, but targeted screening of donors with risk factors (endemic area origin, travel history, or living donors where time permits confirmatory testing) is reasonable.

Geographic and Risk-Based Screening Approach

The screening strategy for HTLV in HSCT donors should be geography-dependent and risk-stratified rather than universal:

• Systematic screening is recommended only in areas of high HTLV endemicity (Caribbean, parts of Africa, South America, Asia, and Oceania) [1, 1
• Selective donor screening in non-endemic areas should focus on donors with risk factors for HTLV-1 infection 1, 2
• Living donors should be screened as time is available to perform confirmatory tests, avoiding unnecessary organ wastage from false-positives 2

Rationale Against Universal Screening in Low-Prevalence Settings

The evidence strongly supports a selective rather than universal approach:

• HTLV seroprevalence in U.S. donors is extremely low at 2.05 per 100,000 donations (0.77 per 100,000 for HTLV-1 specifically) 3
• Current screening assays do not distinguish between HTLV-1 and HTLV-2, leading to significant organ wastage in low seroprevalence areas when false-positives occur 2
• Confirmatory Western blot testing is not always readily available and requires additional time that may not be feasible in deceased donor situations 1, 1

Clinical Context: HSCT vs. Solid Organ Transplantation

While the provided guidelines primarily address solid organ transplantation 1, 1, the principles are relevant but require nuanced application to HSCT:

• HTLV-1 carriers can undergo HSCT without developing ATL or HAM in some cases 4
• Small numbers of HTLV-1-positive cells frequently remain even during complete remission after allo-HSCT, though long-term disease control can be achieved 5
• Atypical HAM can develop rapidly (within 5 months) after allo-HSCT in ATL patients, requiring careful post-transplant monitoring 4

Testing Algorithm When Screening is Performed

When HTLV screening is indicated:

• Initial test: EIA-based serology 1, 1
• If first test is positive: Process a second sample if time is available 1, 1
• If second EIA is negative: Donor can be used 1, 1
• If both tests are positive: Donor should generally be rejected, though donation could be considered for emergency situations, particularly in older recipients 1, 1
• NAT may be useful in identifying false-positive donors 1, 1

Risk of Transmission and Disease Development

The actual transmission risk and clinical consequences remain incompletely defined:

• All transplant donors should be screened for HTLV-1 infection regardless of perceived risk according to one expert review 6, though this conflicts with the more selective approach recommended by transplant societies 2
• The risk of transmission through solid organ transplantation from a confirmed infected donor is unknown, but biologically expected to be higher than blood transfusion due to significant blood volume 6
• Disease can develop within 4 years of transplantation-associated infection, with 11 reports of HAM and 2 of ATL 6
• Pre-existing HTLV-1 infection should not be considered a contraindication to transplantation in recipients 6

Post-Transplant Monitoring

For HTLV-1-infected recipients who undergo HSCT:

• Careful follow-up is essential as immunosuppression may increase the risk of developing HTLV-1-associated disease 2, 4
• Recipients should be counseled that immunosuppression may increase disease risk 2
• Monitor for both ATL and HAM/atypical HAM development post-transplant 4