Abstract
BackgroundDried blood spots are commonly used for sample collection in clinical and non-clinical settings. This method is simple, and biomolecules in the samples remain stable for months at room temperature. In the field, blood samples for the study and diagnosis of malaria are often collected on dried blood spot cards, so development of a biomarker extraction and analysis method is needed.MethodsA simple extraction procedure for the malarial biomarker Plasmodium falciparum histidine-rich protein 2 (HRP2) from dried blood spots was optimized to achieve maximum extraction efficiency. This method was used to assess the stability of HRP2 in dried blood spots. Furthermore, 328 patient samples made available from rural Zambia were analysed for HRP2 using the developed method. These samples were collected at the initial administration of artemisinin-based combination therapy and at several points following treatment.ResultsAn average extraction efficiency of 70% HRP2 with a low picomolar detection limit was achieved. In specific storage conditions HRP2 was found to be stable in dried blood spots for at least 6 months. Analysis of patient samples showed the method to have a sensitivity of 94% and a specificity of 89% when compared with microscopy, and trends in HRP2 clearance after treatment were observed.ConclusionsThe dried blood spot ELISA for HRP2 was found to be sensitive, specific and accurate. The method was effectively used to assess biomarker clearance characteristics in patient samples, which prove it to be ideal for gaining further insight into the disease and epidemiological applications.
Highlights
Dried blood spots are commonly used for sample collection in clinical and non-clinical settings
The technique used for mixing was chosen by extraction into PBST using rotisserie, vortex, and sonicator mixing as well as without mixing
It was found that recovery of histidine-rich protein 2 (HRP2) increased as the energy imparted by the mixing method increased (Fig. 1a)
Summary
Dried blood spots are commonly used for sample collection in clinical and non-clinical settings. This method is simple, and biomolecules in the samples remain stable for months at room temperature. In low-resource areas, the collection of venous blood is not always feasible, so blood samples are often collected via finger prick and stored on filter paper cards. These samples, called dried blood spots (DBS), result in increased biomolecule sample stability compared to liquid samples, as they can be stored in ambient conditions.
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