title: Improving the Specificity of Plasmodium falciparum Malaria Diagnosis in High-Transmission Settings with a Two-Step Rapid Diagnostic Test and Microscopy Algorithm.
abstract: Poor specificity may negatively impact rapid diagnostic test (RDT)-based diagnostic strategies for malaria. We performed real-time PCR on a subset of subjects who had undergone diagnostic testing with a multiple-antigen (histidine-rich protein 2 andpan-lactate dehydrogenase pLDH [HRP2/pLDH]) RDT and microscopy. We determined the sensitivity and specificity of the RDT in comparison to results of PCR for the detection ofPlasmodium falciparummalaria. We developed and evaluated a two-step algorithm utilizing the multiple-antigen RDT to screen patients, followed by confirmatory microscopy for those individuals with HRP2-positive (HRP2+)/pLDH-negative (pLDH-) results. In total, dried blood spots (DBS) were collected from 276 individuals. There were 124 (44.9%) individuals with an HRP2+/pLDH+result, 94 (34.1%) with an HRP2+/pLDH-result, and 58 (21%) with a negative RDT result. The sensitivity and specificity of the RDT compared to results with real-time PCR were 99.4% (95% confidence interval [CI], 95.9 to 100.0%) and 46.7% (95% CI, 37.7 to 55.9%), respectively. Of the 94 HRP2+/pLDH-results, only 32 (34.0%) and 35 (37.2%) were positive by microscopy and PCR, respectively. The sensitivity and specificity of the two-step algorithm compared to results with real-time PCR were 95.5% (95% CI, 90.5 to 98.0%) and 91.0% (95% CI, 84.1 to 95.2), respectively. HRP2 antigen bands demonstrated poor specificity for the diagnosis of malaria compared to that of real-time PCR in a high-transmission setting. The most likely explanation for this finding is the persistence of HRP2 antigenemia following treatment of an acute infection. The two-step diagnostic algorithm utilizing microscopy as a confirmatory test for indeterminate HRP2+/pLDH-results showed significantly improved specificity with little loss of sensitivity in a high-transmission setting.
authors.affiliation: Department of Laboratory Medicine, Mbarara University of Science and Technology, Mbarara, Uganda.
authors.forename: Moses
authors.initials: M
authors.lastname: Murungi
authors.affiliation: Division of General Medicine & Clinical Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
authors.forename: Travis
authors.initials: T
authors.lastname: Fulton
authors.affiliation: Division of General Medicine & Clinical Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
authors.forename: Raquel
authors.initials: R
authors.lastname: Reyes
authors.affiliation: Department of Community Health, Mbarara University of Science and Technology, Mbarara, Uganda.
authors.forename: Michael
authors.initials: M
authors.lastname: Matte
authors.affiliation: Department of Community Health, Mbarara University of Science and Technology, Mbarara, Uganda.
authors.forename: Moses
authors.initials: M
authors.lastname: Ntaro
authors.affiliation: Department of Community Health, Mbarara University of Science and Technology, Mbarara, Uganda.
authors.forename: Edgar
authors.initials: E
authors.lastname: Mulogo
authors.affiliation: Epicentre Mbarara Research Centre, Mbarara, Uganda.
authors.forename: Dan
authors.initials: D
authors.lastname: Nyehangane
authors.affiliation: Division of General Medicine & Clinical Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.|Division of Infectious Diseases, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Juliano
authors.affiliation: Department of Medicine, Harvard Medical School and Massachusetts General Hospital, Boston Massachusetts, USA.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Siedner
authors.affiliation: Department of Laboratory Medicine, Mbarara University of Science and Technology, Mbarara, Uganda.|Epicentre Mbarara Research Centre, Mbarara, Uganda.
authors.forename: Yap
authors.initials: Y
authors.lastname: Boum
authors.affiliation: Division of Infectious Diseases, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA ross.boyce@unchealth.unc.edu.
authors.forename: Ross M
authors.identifier: 0000-0002-9489-6324
authors.initials: RM
authors.lastname: Boyce
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000465:Algorithms; D000953:Antigens, Protozoan / Q000032:analysis*; D000962:Antimalarials / Q000627:therapeutic use; D037621:Artemisinins / Q000627:therapeutic use; D002648:Child; D003955:Diagnostic Tests, Routine / Q000379:methods; D005260:Female; D006801:Humans; D016778:Malaria, Falciparum / Q000175:diagnosis* / Q000188:drug therapy / Q000635:transmission; D008297:Male; D008853:Microscopy / Q000379:methods*; D010963:Plasmodium falciparum / Q000235:genetics*; D011446:Prospective Studies; D011506:Proteins / Q000032:analysis*; D015800:Protozoan Proteins / Q000032:analysis*; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods*; D012680:Sensitivity and Specificity; D014454:Uganda; D055815:Young Adult; D000099053:Histidine-Rich Glycoprotein
chemical_list: D000953:Antigens, Protozoan; D000962:Antimalarials; D037621:Artemisinins; C514457:HRP-2 antigen, Plasmodium falciparum; D011506:Proteins; D015800:Protozoan Proteins; D012337:RNA, Ribosomal, 18S; D000099053:Histidine-Rich Glycoprotein; C031327:artemisinin
keywords: Plasmodium falciparum; antigen specificity; diagnostics; epidemiology; malaria; rapid tests