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Molecular approaches offer a means of testing archived samples stored as dried blood spots in settings where standard blood cultures are not possible. Peripheral blood films are one suggested source of material, although the sensitivity of this approach has not been well defined. Thin blood smears and dried blood spots from a severe pediatric malaria study were assessed using specific polymerase chain reaction (PCR) primers to detect non-typhoidal Salmonella (NTS; MisL gene), Streptococcus pneumoniae (lytA), and Plasmodium falciparum (18S rRNA). Of 16 cases of NTS and S. pneumoniae confirmed on blood culture, none were positive by PCR using DNA extracts from blood films or dried blood spots. In contrast, four of 36 dried blood spots and two of 178 plasma samples were PCR positive for S. pneumoniae, despite negative bacterial blood cultures, suggesting false positives. Quantitative assessment revealed that the effective concentration of P. falciparum DNA in blood films was three log orders of magnitude lower than for dried blood spots. The P. falciparum kelch13 gene could not be amplified from blood films. These findings question the value of blood PCR-based approaches for detection of NTS and S. pneumoniae, and show that stored blood films are an inefficient method of studying P. falciparum.

Original publication

DOI

10.4269/ajtmh.15-0532

Type

Journal article

Journal

Am J Trop Med Hyg

Publication Date

02/2016

Volume

94

Pages

322 - 326

Keywords

Blood Specimen Collection, Child, DNA, Bacterial, DNA, Protozoan, Humans, Malaria, Falciparum, Plasmodium falciparum, Pneumococcal Infections, Polymerase Chain Reaction, Salmonella Infections, Sensitivity and Specificity, Tanzania