Field assessment of dried Plasmodium falciparum samples for malaria rapid diagnostic test quality control and proficiency testing in Ethiopia

Abstract

BackgroundRapid diagnostic tests (RDTs) are now widely used for laboratory confirmation of suspected malaria cases to comply with the World Health Organization recommendation for universal testing before treatment. However, many malaria programmes lack quality control (QC) processes to assess RDT use under field conditions. Prior research showed the feasibility of using the dried tube specimen (DTS) method for preserving Plasmodium falciparum parasites for use as QC samples for RDTs. This study focused on the use of DTS for RDT QC and proficiency testing under field conditions.MethodsDTS were prepared using cultured P. falciparum at densities of 500 and 1,000 parasites/μL; 50 μL aliquots of these along with parasite negative human blood controls (0 parasites/μL) were air-dried in specimen tubes and reactivity verified after rehydration. The DTS were used in a field study in the Oromia Region of Ethiopia. Replicate DTS samples containing 0, 500 and 1,000 parasites/μL were stored at 4°C at a reference laboratory and at ambient temperatures at two nearby health facilities. At weeks 0, 4, 8, 12, 16, 20, and 24, the DTS were rehydrated and tested on RDTs stored under manufacturer-recommended temperatures at the RL and on RDTs stored under site-specific conditions at the two health facilities. Reactivity of DTS stored at 4°C at the reference laboratory on RDTs stored at the reference laboratory was considered the gold standard for assessing DTS stability. A proficiency-testing panel consisting of one negative and three positive samples, monitored with a checklist was administered at weeks 12 and 24.ResultsAt all the seven time points, DTS stored at both the reference laboratory and health facility were reactive on RDTs stored under the recommended temperature and under field conditions, and the DTS without malaria parasites were negative. At the reference laboratory and one health facility, a 500 parasites/μL DTS from the proficiency panel was falsely reported as negative at week 24 due to errors in interpreting faint test lines.ConclusionsThe DTS method can be used under field conditions to supplement other RDT QC methods and health worker proficiency in Ethiopia and possibly other malaria-endemic countries.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-014-0524-z) contains supplementary material, which is available to authorized users.

External quality assessment in resource–limited countries

“…Methods for preparing stable positive controls from cultured P. falciparum using DBS and dried tube specimens (DTS) have been demonstrated ( 68 , 69 ). Tamiru et al reported performance of DTS PT challenges at 1000 and 500 parasites/µL in a field trial in Ethiopia; false negative DTS at 500 parasites/μL were reported after 24 weeks’ storage due to errors in interpreting faint test lines ( 70 ). Aggett reported stability of CD4 PT samples as only 7 days at ambient temperature and 14 days when refrigerated ( 32 ).…”

Evaluasi Penggunaan Nilai Formulasi Sebagai Nilai Acuan Dalam Penyelenggaraan Uji Profisiensi Air Permukaan

“…Partisipasi dalam skema UP diperlukan dan bermanfaat bagi semua laboratorium pengujian. Banyak skema UP telah dilakukan di seluruh dunia dalam berbagai bidang pengujian, seperti di bidang analisis lingkungan (Asiah, 2017), analisis air (Kim et al, 2010), sifat fisik (Hegazy et al, 2010), serum manusia (Carter et.al, 2010), klinis (Tamiru et al, 2015), mikrobiologi (Smith, 2015), dan makanan (Dajay et al, 2019)…”

Stabilization of RDT target antigens present in dried Plasmodium falciparum-infected samples for validating malaria rapid diagnostic tests at the point of care

“…While the world waits for the complete development of PCW, dried Plasmodium falciparum -infected samples were developed as possible cheaper alternatives in monitoring the performance of RDT in routine use [ 9 ]. The dried P. falciparum -infected sample tubes contain the RDT target antigens; histidine rich protein 2 (HRP2), lactate dehydrogenase (LDH) and aldolase [ 9 , 10 ]. The challenge facing their applicability is protein degradation and rapid loss of reactivity during prolonged storage at ambient conditions [ 9 , 10 ].…”

“…The dried P. falciparum -infected sample tubes contain the RDT target antigens; histidine rich protein 2 (HRP2), lactate dehydrogenase (LDH) and aldolase [ 9 , 10 ]. The challenge facing their applicability is protein degradation and rapid loss of reactivity during prolonged storage at ambient conditions [ 9 , 10 ]. Furthermore, it is challenging to establish well characterized samples for specific RDTs, as well as quantification of target antigens.…”