Reducing transfusion-associated malaria in Pakistan: an algorithmic approach

Abstract

Blood transfusions represent a small but significant source of malaria transmission. Most blood banks rely solely on donor questioning to exclude malaria patients from donating blood. No guidelines exist for in vitro screening of donor blood for malaria in endemic areas. Possible laboratory screening techniques include: microscopy; enzyme-linked immunosorbent assay (ELISA) antibody testing; polymerase chain reaction (PCR) testing; and rapid diagnostic antigen tests. However, all these modalities have diagnostic limitations. Based on a best evidence review, we present recommendations using an algorithmic approach to blood screening for malaria in Pakistan. This algorithm considers regional endemicity for malaria, as well as a detailed donor history, in order to decide whether donor blood should be tested with rapid antigen testing. We hope this algorithm will assist in the development of future national guidelines for screening blood for malaria that will reduce the risk of blood-borne transmission.

What is the best strategy for the prevention of transfusion-transmitted malaria in sub-Saharan African countries where malaria is endemic?

“…Only a few parasites in a unit of blood are sufficient to cause infections in susceptible individuals namely children, pregnant women and immunocompromized patients [20]. TTM presents, therefore, a public health risk, requiring effective methods of donor screening [33]. Any malaria screening test used by the transfusion services in SSA needs to be highly sensitive [20,34].…”

“…RDTs detect Plasmodium -specific parasite proteins, such as pan-malarial lactate dehydrogenase (pLDH), and P. falciparum specific histidine-rich protein 2 (HRP2). Most of these assays are in a ‘dipstick’ format that can be used with minimal training, are field applicable, and provide a result within 10-20 minutes [27,33,39]. However, RDTs methods have not offered improved sensitivity over microscopy, and their sensitivity decreases as parasitaemia falls below 100 parasites/μL.…”

“…Also, false positives are observed, especially after treatment, as the parasite antigens detected can remain in the circulation following parasite clearance, this being especially the case for the HRP2 antigen-based tests. Eventually, current RDTs are either specific to P. falciparum , or they cannot distinguish between the parasite species present [33,35]. Heutmekers et al using a RDT CareStart pLDH showed for instance that overall sensitivity for P. falciparum and P. vivax was good, but poor for P. ovale and P. malariae [40].…”

“…Owing to its prohibitive cost as well as the fact that the infrastructure needed is scarcely available in SSA malaria-endemic zones, which by the way are almost all resource-limited settings, PCR is not currently, or in the foreseeable future, a viable alternative for the screening of blood donations [27]. PCR may be probably best used in a stepwise fashion when other testing modalities are non-diagnostic but when the index of suspicion for malaria is high [33]. …”

“…But this strategy lacks the capacity of eliminating asymptomatic but malaria-parasitaemic blood donors [30,42]. To be useful, the medical selection through donor questionnaire must be integrated in an algorithm including other screening tools [33]. …”