Investigating portable fluorescent microscopy (CyScope) as an alternative rapid diagnostic test for malaria in children and women of child-bearing age.
BACKGROUND
Prompt and correct diagnosis of malaria is crucial for accurate epidemiological assessment and better case management, and while the gold standard of light microscopy is often available, it requires both expertise and time. Portable fluorescent microscopy using the CyScope offers a potentially quicker, easier and more field-applicable alternative. This article reports on the strengths, limitations of this methodology and its diagnostic performance in cross-sectional surveys on young children and women of child-bearing age.


METHODS
552 adults (99% women of child-bearing age) and 980 children (99% ≤ 5 years of age) from rural and peri-urban regions of Ugandan were examined for malaria using light microscopy (Giemsa-stain), a lateral-flow test (Paracheck-Pf) and the CyScope. Results from the surveys were used to calculate diagnostic performance (sensitivity and specificity) as well as to perform a receiver operating characteristics (ROC) analyses, using light microscopy as the gold-standard.


RESULTS
Fluorescent microscopy (qualitative reads) showed reduced specificity (<40%), resulting in higher community prevalence levels than those reported by light microscopy, particularly in adults (+180% in adults and +20% in children). Diagnostic sensitivity was 92.1% in adults and 86.7% in children, with an area under the ROC curve of 0.63. Importantly, optimum performance was achieved for higher parasitaemia (>400 parasites/μL blood): sensitivity of 64.2% and specificity of 86.0%. Overall, the diagnostic performance of the CyScope was found inferior to that of Paracheck-Pf.


CONCLUSIONS
Fluorescent microscopy using the CyScope is certainly a field-applicable and relatively affordable solution for malaria diagnoses especially in areas where electrical supplies may be lacking. While it is unlikely to miss higher parasitaemia, its application in cross-sectional community-based studies leads to many false positives (i.e. small fluorescent bodies of presently unknown origin mistaken as malaria parasites). Without recourse to other technologies, arbitration of these false positives is presently equivocal, which could ultimately lead to over-treatment; something that should be further explored in future investigations if the CyScope is to be more widely implemented.
Sousa-Figueiredo
José Carlos
JC
WHO Collaborating Centre Schistosomiasis, Wolfson Wellcome Biomedical Laboratories, Department of Zoology, Natural History Museum, London SW7 5BD, UK. j.figueiredo@nhm.ac.uk
Oguttu
David
D
Adriko
Moses
M
Besigye
Fred
F
Nankasi
Andrina
A
Arinaitwe
Moses
M
Namukuta
Annet
A
Betson
Martha
M
Kabatereine
Narcis B
NB
Stothard
J Russell
JR
D000293:Adolescent; D000328:Adult; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D003955:Diagnostic Tests, Routine / Q000379:methods*; D005260:Female; D006801:Humans; D007223:Infant; D008288:Malaria / Q000175:diagnosis*; D008297:Male; D008856:Microscopy, Fluorescence / Q000379:methods*; D008875:Middle Aged; D010274:Parasitology / Q000379:methods*; D011237:Predictive Value of Tests; D012372:ROC Curve; D012424:Rural Population; D013997:Time Factors; D014454:Uganda; D055815:Young Adult
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