Dried plasma spot testing – the answer for making blood transfusion testing safer in africa?

Pistorius, Charlotte (2018-12)

Thesis (MMed)--Stellenbosch University, 2018.

Thesis

ENGLISH ABSTRACT: Sub-Saharan Africa (SSA) has a unique set of challenges pertaining to blood transfusion. Two of the largest contributing factors are: (1) the most common disease states in SSA require large amounts of blood as a lifesaving intervention e.g. malaria, and (2) the highest burden of infectious diseases transmissible through transfusion (Tapko, Toure, & Sambo, 2014) is found in SSA. This has often led to the dichotomous donor base that exists in SSA, consisting of Voluntary Non-remunerated Blood donors (VNBD) and family or replacement donors (FRD), since transfusion centres are unable to supply the demand when relying only on VNBD. VNBD are the safest blood donors as they have no monetary incentives and are under no direct social pressure to donate. Monetary incentives have been shown to entice individuals that know or suspect themselves to be infected with a blood borne agent to donate blood. Nucleic Acid Testing (NAT) in conjunction with serological testing is the gold standard for testing, however the vast distances and high temperatures of SSA makes transport of traditional plasma samples a logistical nightmare. Many publications evaluating the stability, suitability and ease of use of dried blood spot (DBS) and dried plasma spot (DPS) for NAT have been published. Generally results have been shown to be comparable to traditional plasma samples. DBS are being used successfully in the early infant diagnosis (EID) programs for HIV by means of PCR testing especially in Africa. Ethical approval was obtained to conduct a study to determine whether DBS and/or DPS testing would be suitable for use in a resource limited setting for blood screening. Two cohorts were included. Cohort A consisted of 900 de-identified negative new donor samples. Cohort B consisted of 100 de-identified confirmed positive donor samples, 9 procured reactive samples, and a contamination panel. After routine donor testing was completed at Western Province Blood Transfusion Service, one DBS sample and one DPS sample for each blood donor was prepared and analysed with the Ultrio Elite Assay on the Panther analyser (Hologic Inc., USA). Logistically DBS/DPS is well suited for the resource-poor countries as samples are: a.Easy to obtain (fingerpick samples could be used). b.Transport is simplified as samples will not leak or haemolyse due to high temperatures. c.Samples can be stored at room temperature. DBS/DPS samples demonstrated superb specificity. DPS samples would be suited for screening blood and reduced cost involved in NAT testing provided that the HBV sensitivity is increased. Further detailed economic viability and large-scale studies need to be performed to determine sensitivity and specificity within a specific population.

AFRIKAANSE OPSOMMING: Bloedoortapping in Sub-Sahara Afrika(SSA) word geteister deur unieke uitdagings. Die twee grootste bydraende faktore is: 1)die mees algemene infeksies in SSA vereis menige bloedoortappings as ingrypende lewensredendeen lewensverbeterende terapie bv. Malaria, 2)die grootse las van aansteeklike siektes, wat deur bloedoortapping oorgedra word, word in SSAaangetref (Tapko, Toure and Sambo, 2014). Hierdie twee faktore het bygedra tot die ontstaan van die tweeledigeskenskersbasis wat in SSA gevind word. Die tweeledigeskenkersbais bestaan uit vrywillige onvergoede bloedskenkers(VOBS) en familie lede en/of vervangings skenkers(VS). Daar word dikwels staat gemaak op VS as gevolg van die feit dat bloedoortappingssentrums nie in staat is om die aanvraag te voorsien wanneer daar slegs op VOBS staat gemaak word nie. VOBS is die veiligste bloedskenkers omdat hulle geen monetêre motiewe het nie en onder geen direkte sosiale druk verkeer om te skenk nie. Monetêre motiewe kan individue, wie kennis dra of vermoed dat hulle bloed besmet is met oordraagbare agente, aanspoor om te skenk. Die kombinasie van nukleïensuurtoetsing (NAT) en serologiese toetsing is die goue standaard vir bloedoortappings-siftingstoetse, maar die lang afstande en hoë temperature van SSA maak die vervoer van tradisionele plasma monsters 'n logistieke nagmerrie. Menige publikasies oor die stabiliteit, geskiktheid en gemak van die gebruik van gedroogde bloed kol (DBK) en gedroogde plasma kol (DPK) vir NAT is reeds gepubliseer. Oor die algemeen het die resultate vergelykbaar met tradisionele plasma monsters vertoon. DBK word veral in Afrika suksesvol gebruik in die vroeë babadiagnose-programme (EID) vir die toetsing van menslike immuniteits virus deur middel van polimerase kettingreaksie. Etiese goedkeuring was verkry vir die studie wat beoog om te bepaal of DBK/DPK geskik sal wees om te gebruik vir siftings-bloedoortappingstoetse in 'n hulpbron beperkte omgewing. Twee kohorte was ingesluit by die studie. Kohort A het bestaan uit 900 gedeïdentifiseerde negatiewe nuwe skenkermonsters. Kohort B het bestaan uit 100 gedeïdentifiseerde bevestigde positiewe skenkersmonsters, nege aangekoopte reaktiewe monsters en 'n besmettings paneel. Nadat roetine siftings-bloedoortappingstoetse deur dieWestelike Provinsie Bloedoortappingsdiens voltooi was, is een DBK monster en een DPK monster vir elke bloedskenker voorberei en getoets deur die Ultrio Elite reagens op die Panther instrument (Hologic Inc., VSA). DBK/DPK is logisties geskik vir hulpbronbeperkte lande want die monsters: a. Is maklik om te verkry (Vingerprikmonsters kan gebruik word). b. Vervoer van monsters kan vereenvoudig word omdat monsters nie lek of hemoliseer weens hoë temperature nie. c. Kan teen kamertempuratuur geberg word. DBK/DPK het uitstekende spesifisiteit gedemonstreer (100%). DPK sal geskik wees vir die toeting van bloed en vermindering in koste verbonde aan NAT toetsing, slegs as die HBV sensitiwiteit verhoog word. Verdere ekonomiese, lewensvatbare en grootskaalse studies moet uitgevoer word om die sensitiwiteit en spesifisiteit binne 'n spesifieke bevolking te bepaal.

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