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Journal of Clinical Microbiology, March 2001, p. 1025-1031, Vol. 39, No. 3
Communicable Diseases Research Centre,
National Institute of Health Research and
Development,1 and Directorate General of
Communicable Disease Control and Environmental
Health,3 Jakarta, Indonesia, and
Tropical Medicine and International Health Unit, Menzies
School of Health Research and Royal Darwin Hospital Clinical
School, Darwin, Northern Territory, Australia2
Received 28 July 2000/Returned for modification 23 October
2000/Accepted 20 December 2000
A problem with rapid Plasmodium falciparum-specific
antigen histidine-rich protein 2 (HRP2) detection tests for malaria is the persistence of antigen in blood after the disappearance of asexual-stage parasitemia and clinical symptoms, resulting in false-positive (FP) test results following treatment. The ICT P.f/P.v
immunochromatographic test detects both HRP2 and a panmalarial antigen
(PMA) found in both P. falciparum and Plasmodium
vivax. To examine posttreatment antigen persistence with this
test and whether persistent sexual-stage forms (gametocytes) are a
cause of FP tests after treatment, we compared serial antigen test
results with microscopy results from patients symptomatic with P. falciparum malaria in Indonesia for 28 days following treatment
with chloroquine (CQ; n = 66),
sulfadoxine-pyrimethamine (SP; n = 36), and artesunate plus sulfadoxine-pyrimethamine (ART + SP;
n = 15). Persistent FP antigenemia following SP
treatment occurred in 29% (HRP2) and 42% (PMA) of the patients on day
7 and in 10% (HRP2) and 23% (PMA) on day 14. The high rates of
persistent HRP2 and PMA antigenemia following CQ and SP treatment were
strongly associated with the presence of gametocytemia, with the
proportion with gametocytes on day 7 posttreatment being significantly
greater in those with FP results than in those with true-negative PMA
and HRP2 results. Gametocyte frequency on day 14 post-SP treatment was
also greater in those with FP PMA results. Following SP treatment, PMA
persisted longer than HRP2, giving an FP diagnosis of P. vivax in up to 16% of patients on day 14, with all FP P. vivax diagnoses having gametocytemia. In contrast, PMA was
rapidly cleared following ART + SP treatment in association with
rapid clearance of gametocytemia. Gametocytes appear to be an important
cause of persistent posttreatment panmalarial antigenemia in areas
of endemicity and may also contribute in part to
persistent HRP2 antigenemia following treatment.
0095-1137/01/$04.00+0 DOI: 10.1128/JCM.39.3.1025-1031.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Persistent ICT Malaria P.f/P.v Panmalarial and HRP2 Antigen
Reactivity after Treatment of Plasmodium falciparum
Malaria Is Associated with Gametocytemia and Results in
False-Positive Diagnoses of Plasmodium vivax in
Convalescence
*
Corresponding author. Mailing address: Tropical
Medicine and International Health Unit, Menzies School of Health
Research and Royal Darwin Hospital Clinical School, P.O. Box 41096, Casuarina, Darwin, Northern Territory 0811, Australia. Phone: 61-8-8922 8932. Fax: 61-8-8927 5187. E-mail:
anstey{at}menzies.edu.au.
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