Highly Sensitive Detection of Malaria Parasitemia in a Malaria-Endemic Setting: Performance of a New Loop-Mediated Isothermal Amplification Kit in a Remote Clinic in Uganda

• Published in: The Journal of infectious diseases Vol. 208; no. 4; pp. 645 - 652
• Main Authors: Hopkins, Heidi, González, Iveth J., Polley, Spencer D., Angutoko, Patrick, Ategeka, John, Asiimwe, Caroline, Agaba, Bosco, Kyabayinze, Daniel J., Sutherland, Colin J., Perkins, Mark D., Bell, David
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 15.08.2013
• Subjects: Adolescent; Adult; Aged; Aged, 80 and over; Biological and medical sciences; Blood; Child; Child, Preschool; Endemic Diseases; Female; Fluorescence; Fundamental and applied biological sciences. Psychology; Furunculosis; Human protozoal diseases; Humans; Infections; Infectious diseases; Lamps; Major and Brief Reports; Malaria; Malaria, Falciparum - diagnosis; Malaria, Falciparum - epidemiology; Male; Medical sciences; Microbiology; Microscopy; Middle Aged; Molecular Diagnostic Techniques - methods; Nucleic Acid Amplification Techniques - methods; Parasitemia; Parasitemia - diagnosis; Parasites; Parasitic diseases; Parasitology - methods; Plasmodium falciparum - isolation & purification; Polymerase chain reaction; Protozoal diseases; Rural Population; Sensitivity and Specificity; Uganda; Young Adult; Uganda; East Africa; Sub-Saharan Africa; Africa; Infection; Protozoal disease; Malaria; Loop mediated isothermal amplification reaction; Tropical zone; Equatorial zone; Parasitosis; Detection; Parasitemia; Plasmodium falciparum; DNA; Africa; Uganda; diagnosis; LAMP; loop-mediated isothermal amplification; malaria; PCR; polymerase chain reaction; sensitivity and specificity; molecular diagnosis
• ISSN: 0022-1899; 1537-6613; 1537-6613
• DOI: 10.1093/infdis/jit184

Background. Current malaria diagnostic tests, including microscopy and antigen-detecting rapid tests, cannot reliably detect low-density infections. Molecular methods such as polymerase chain reaction (PCR) are highly sensitive but remain too complex for field deployment. A new commercial molecular assay based on loop-mediated isothermal amplification (LAMP) was assessed for field use. Methods. Malaria LAMP (Eiken Chemical, Japan) was evaluated for samples from 272 outpatients at a rural Ugandan clinic and compared with expert microscopy, nested PCR, and quantitative PCR (qPCR). Two technicians performed the assay after 3 days of training, using 2 alternative blood sample-preparation methods and visual interpretation of results by fluorescence assay. Results. Compared with 3-well nested PCR, the sensitivity of both LAMP and single-well nested PCR was 90%; the microscopy sensitivity was 51%. For samples with a Plasmodium falciparum qPCR titer of ≥2 parasites//μL, LAMP sensitivity was 97.8% (95% confidence interval, 93.7%-99.5%). Most false-negative LAMP results involved samples with parasitemia levels detectable by 3-well nested PCR but very low or undetectable by qPCR. Conclusions. Malaria LAMP in a remote Ugandan clinic achieved sensitivity similar to that of single-well nested PCR in a United Kingdom reference laboratory. LAMP dramatically lowers the detection threshold achievable in malaria-endemic settings, providing a new tool for diagnosis, surveillance, and screening in elimination strategies.