Acta Tropica 112 (2009) 277–282 Contents lists available at ScienceDirect Acta Tropica journal homepage: www.elsevier.com/locate/actatropica Plasmodium falciparum parasite infection prevalence from a household survey in Zambia using microscopy and a rapid diagnostic test: Implications for monitoring and evaluation Joseph Keating a,∗ , John M. Miller b , Adam Bennett a , Hawela B. Moonga c , Thomas P. Eisele a a Department of International Health and Development, Tulane University School of Public Health and Tropical Medicine, 1440 Canal Street, Suite 2200, New Orleans, LA, 70112, United States of America b PATH Malaria Control and Evaluation Partnership in Africa (MACEPA), Chainama Hospital, Lusaka, Zambia c National Malaria Control Centre, Ministry of Health Zambia, Chainama Hospital, Lusaka, Zambia article info Article history: Received 24 June 2009 Received in revised form 5 August 2009 Accepted 6 August 2009 Available online 13 August 2009 Keywords: Microscopy RDT Population-based survey Malaria Monitoring and evaluation Zambia abstract This paper presents estimates of P. falciparum infection prevalence in children under 5 years old in the context of a population-based household survey in Luangwa District (Lusaka Province), Zambia, an area where greater than 75% of households possess at least one insecticide-treated mosquito net (ITN). The sen- sitivity and specificity of an HRP-2 rapid diagnostic test (RDT) (ICT Malaria Pf ® ) compared to microscopy, as well as factors associated with discordant diagnostic results are also presented. P. falciparum infec- tion prevalence was estimated at 7.0% (95% CI 4.9–9.0%) using microscopy. Using microscopy as the gold standard, the sensitivity of the HRP-2 RDT was 100% and specificity was 91.5%; positive predictive value was estimated to be 46.7% (95% CI 36.3–57.4%). RDT discordance, or HRP-2 false positivity, was highest among older children, those in the northern part of Luangwa District, and those with a reported history of antimalarial treatment. These data suggest microscopy should remain the gold standard for estimating malaria parasite point prevalence from household surveys for monitoring and evaluation purposes. © 2009 Elsevier B.V. All rights reserved. 1. Introduction With increased funding from international donors, a concerted effort is underway to scale up malaria control interventions in malaria endemic countries of sub-Saharan Africa (SSA). Population- based household surveys have become the standard to monitor malaria control intervention coverage and malaria parasite infec- tion in children (WHO, 2008; Zambia MoH, 2006; Zambia MoH, 2008; Unicef, 2007). Standardizing the measurement of such indi- cators is crucial for comparing progress over time and across countries. Microscopy remains the gold standard for diagnosing malaria parasite infections in clinical practice and research. However, recently developed rapid diagnostic tests (RDTs) allow for the detection of Plasmodium parasites from human blood samples without a microscope. This advancement has been critical for expanding access to accurate diagnosis of malaria within areas of Africa where microscopy in unavailable. RDTs are also used in large population-based household surveys that include biomarkers ∗ Corresponding author. Tel.: +1 504 988 1348; fax: +1 504 988 3653. E-mail addresses: jkeating@tulane.edu (J. Keating), jmiller@path.org (J.M. Miller), abennett@tulane.edu (A. Bennett), mhawela@yahoo.co.uk (H.B. Moonga), teisele@tulane.edu (T.P. Eisele). for malaria, such as the Malaria Indicator Survey (MIS), to identify infected children so that they can be treated with an antimalarial immediately upon detection. The most frequently used RDT for identifying a Plasmodium falciparum infection detects the parasite antigen histidine-rich protein 2 (HRP-2); other RDTs detect malaria parasite lac- tate dehydrogenase or aldolase, which are not species-specific. The accuracy of HRP-2 RDTs compared to microscopy for the diagnosis of P. falciparum infections associated with fever has been well documented in clinical settings, with sensitivity typ- ically >90% and specificity >85%, although the sensitivity has been observed to decline with decreasing parasite densities (Wongsrichanalai et al., 2007; De Oliveira et al., 2009; WHO, 2009). A problem particular to HRP-2 RDTs is the potential for false positive results due to the detection of circulating HRP-2 antigens (for up to several weeks) following an infection that was elimi- nated with treatment (Hopkins et al., 2007; Tjitra et al., 2001; Singh and Shukla, 2002; Mayxay et al., 2001). For case management in malaria endemic settings, the potential for HRP-2 RDTs to yield false positives is acceptable, given that the test often achieves high sensi- tivity for detecting true positives. However, the detection of recent past infections by HRP-2 RDTs for estimating P. falciparum infec- tion prevalence under household survey conditions would result in an overestimate of the true point prevalence of infection, as 0001-706X/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.actatropica.2009.08.011