(P-BC-60) Lessons Learned from Assessing a Donor Screening Malaria Nucleic Acid Test with a Spike and Recovery Approach.

Background/Case Studies: In 2023, a probable case of transfusion-transmitted-malaria (TTM) was linked to a Canadian blood donor with an unrecognized asymptomatic semi-immune malaria infection and a parasitemia of 0.0004%. A later risk-based decision-making process (RBDM) proposed implementing a malaria/Plasmodium nucleic acid testing (NAT) technology at Canadian Blood Services. The Roche cobas Malaria Assay (Roche Diagnostics GmbH, Mannheim, Germany) offers a molecular diagnostic solution for genus level detection of Plasmodium spp., P. falciparum, P. malariae, P. vivax, P. ovale, and zoonotic species (e.g. P. cynomolgi). The malaria assay is intended for use in blood donor screening. This study describes lessons learned from a series of spike and recovery experiments carried out in the Canadian Blood Services Surveillance and Discovery Laboratory (SDL).

Study

Design/Methods: Laboratory processes were developed at the SDL (Ottawa, ON) for testing with the Roche cobas Malaria Assay on the Roche 6800 platform (Roche Diagnostics GmbH, Mannheim, Germany). Known NAT-positive specimens identified at a reference clinical microbiology laboratory (ProvLab Alberta, Edmonton, AB, Canada) were noted for original crossing threshold (Ct), infected red blood cells/ml and % parasitemia. Specimens were spiked into Roche Whole Blood Collection tubes (RWBCT; Roche Diagnostics GmbH, Mannheim, Germany) and transported to the SDL for testing. Results were reviewed by technologists and microbiologists at the laboratory. Lessons learned were developed by technologists and microbiologists after the review of results.

Results/Findings: Table. Lessons learned from a malaria spike and recovery testing project.

Variable	Information generated	Implication
Limits of detection	100% detection rates of P. falciparum dilutions (100 iRBCs/ml) were within 1 log of the 10 iRBC/ml (100% reactive) from the package insert of the commercial test.	Pre-analytical and analytical processes ensured successful identification of spiked specimens.
Comparison of positivity to initial reference laboratory Ct value	The Roche NAT was positive at dilutions past the Ct cutoff of the reference laboratory assay.	Clinicians managing donors with a positive Roche NAT result should consider clinical tests characteristics.
Comparison of parasitemia to prior TTM case	The detectability of parasitemia was 2-3 logs more sensitive than the implicated donor parasitemia from the TTM case.	The assay would have allowed for the interdiction of Plasmodium-positive components.

Conclusions: This approach ensures high analytical sensitivity for detection of very low parasitemia levels. Findings highlight the assay's suitability for blood donor screening in our setting and work is ongoing to operationalize this approach.