title: PCR-based pooling of dried blood spots for detection of malaria parasites: optimization and application to a cohort of Ugandan children.
abstract: Sensitive, high-throughput methods to detect malaria parasites in low-transmission settings are needed. PCR-based pooling strategies may offer a solution. We first used laboratory-prepared samples to compare 2 DNA extraction and 4 PCR detection methods across a range of pool sizes and parasite densities. Pooled Chelex extraction of DNA, followed by nested PCR of cytochrome b, was the optimal strategy, allowing reliable detection of a single low-parasitemic sample (100 parasites/μl) in pool sizes up to 50. This PCR-based pooling strategy was then compared with microscopy using 891 dried blood spots from a cohort of 77 Ugandan children followed for 2 years in an urban setting of low endemicity. Among 419 febrile episodes, 35 cases of malaria were detected using the PCR-based pooling strategy and 40 cases using microscopy. All five cases of malaria not detected by PCR were from samples stored for >2 years with parasitemia of <6,000/μl, highlighting the issue of possible DNA degradation with long-term storage of samples. Among 472 samples collected from asymptomatic children as part of routine surveillance, 15 (3.2%) were positive by PCR-based pooling compared to 4 (0.8%) by microscopy (P = 0.01). Thus, this PCR-based pooling strategy for detection of malaria parasites using dried blood spots offers a sensitive and efficient approach for malaria surveillance in low-transmission settings, enabling improved detection of asymptomatic submicroscopic infections and dramatic savings in labor and costs.
authors.affiliation: Department of Global Health Sciences, Division of Pediatric Infectious Diseases, University of California, San Francisco, San Francisco, CA 94105, USA. hsiangm@peds.ucsf.edu
authors.forename: Michelle S
authors.initials: MS
authors.lastname: Hsiang
authors.forename: Michael
authors.initials: M
authors.lastname: Lin
authors.forename: Christian
authors.initials: C
authors.lastname: Dokomajilar
authors.forename: Jordan
authors.initials: J
authors.lastname: Kemere
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Pilcher
authors.forename: Grant
authors.initials: G
authors.lastname: Dorsey
authors.forename: Bryan
authors.initials: B
authors.lastname: Greenhouse
mesh_terms: D001769:Blood / Q000469:parasitology*; D002648:Child; D002675:Child, Preschool; D016054:DNA, Protozoan / Q000235:genetics / Q000302:isolation & purification; D003890:Desiccation; D006801:Humans; D007223:Infant; D008288:Malaria / Q000175:diagnosis*; D008853:Microscopy / Q000379:methods; D010274:Parasitology / Q000379:methods*; D016133:Polymerase Chain Reaction / Q000379:methods*; D012680:Sensitivity and Specificity; D013048:Specimen Handling / Q000379:methods*; D014454:Uganda
chemical_list: D016054:DNA, Protozoan