A comparison of the sensitivities of detection of Plasmodium falciparum gametocytes by magnetic fractionation, thick blood film microscopy, and RT-PCR.
BACKGROUND
The magnetic properties of Plasmodium-infected erythrocytes have been exploited for different clinical and research purposes. A recent study in a rural clinical setting in Papua New Guinea has demonstrated that Plasmodium falciparum gametocyte detection is facilitated by magnetic deposition microscopy but no study has yet determined the relative sensitivity and limit of detection of a magnetic fractionation technique. The present study compares the detection limit and sensitivity of a technique based on the use of commercially available magnetic fractionation columns with those for thick blood film microscopy and reverse transcriptase polymerase chain reaction (RT-PCR) methods.


METHODS
Gametocyte detection in six series of dilutions of cultured P. falciparum parasites with known gametocytaemia was conducted using magnetic fractionation, thick blood film, and RT-PCR techniques.


RESULTS
The preparations obtained by the magnetic fractionation method were of thin film quality allowing easy gametocyte identification by light microscopy. Magnetic fractionation had a higher sensitivity and approximately two orders of magnitude better limit of detection than thick blood film microscopy. Gametocytes were also more readily detectable on the magnetically fractionated preparations. Magnetic fractionation had a similar limit of detection to that of RT-PCR.


CONCLUSIONS
Magnetic fractionation is a highly sensitive and convenient method for gametocyte detection in comparison with the standard thick blood film and RT-PCR methods, and could readily be adapted to field application.
Karl
Stephan
S
School of Physics, M013, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Australia. karls01@student.uwa.edu.au
Davis
Timothy M E
TM
St-Pierre
Tim G
TG
D000818:Animals; D001769:Blood / Q000469:parasitology*; D017931:DNA Primers; D006801:Humans; D008280:Magnetics; D016778:Malaria, Falciparum / Q000097:blood / Q000175:diagnosis / Q000469:parasitology*; D008853:Microscopy / Q000379:methods*; D008969:Molecular Sequence Data; D010963:Plasmodium falciparum / Q000235:genetics / Q000302:isolation & purification*; D015800:Protozoan Proteins / Q000235:genetics; D016053:RNA, Protozoan / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods*; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA; D018709:Statistics, Nonparametric
D017931:DNA Primers; D015800:Protozoan Proteins; D016053:RNA, Protozoan