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Rapid diagnostic tests (RDTs) represent an alternative to microscopy for malaria diagnosis and have shown high sensitivity and specificity in a variety of study settings. Current World Health Organization (WHO) guidelines for quality control of RDTs provide detailed instructions on pre-field testing, but offer little guidance for quality assurance once RDTs are deployed in health facilities. From September 2006 to April 2007, we introduced a histidine-rich protein II (HRP2)-based RDT (Paracheck) for suspected malaria cases five years of age and older in nine health facilities in Rufiji District, Tanzania, to assess sensitivity and specificity of RDTs in routine use at rural health facilities. Thick blood smears were collected for all patients tested with RDTs and stained and read by laboratory personnel in each facility. Thick smears were subsequently reviewed by a reference microscopist to determine RDT sensitivity and specificity. In all nine health facilities, there were significant problems with the quality of staining and microscopy. Sensitivity and specificity of RDTs were difficult to assess given the poor quality of routine blood smear staining. Mean operational sensitivity of RDTs based on reference microscopy was 64.8%, but varied greatly by health facility, range 18.8–85.9%. Sensitivity of RDTs increased with increasing parasite density. Specificity remained high at 87.8% despite relatively poor slide quality. Institution of quality control of RDTs based on poor quality blood smear staining may impede reliable measurement of sensitivity and specificity and undermine confidence in the new diagnostic. There is an urgent need for the development of alternative quality control procedures for rapid diagnostic tests that can be performed at the facility level.
Received January 4, 2008. Accepted for publication June 16, 2008.
Acknowledgments: We sincerely thank Dr. David Bell of the WHO Western Pacific Regional Office in Manila for lot quality testing our RDTs and for his guidance and continued support of this implementation project. We also thank John Barnwell, Kathy Grady, and Venkatachalam Udhayakumar at the CDC Malaria Reference Laboratory for conducting further lot testing of our RDTs. Additionally, we would like to recognize the contributions of the field team (Bakari Kissa, Buzingwa Bofu, Abdallah Bakari) and the district medical officer in Rufiji, Dr. Said Mkikima, for their hard work and perseverance through these implementation challenges.
Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention.
Disclosure: Some data from this manuscript was presented at the 56th Annual Meeting of the American Society of Tropical Medicine and Hygiene (ASTMH), Philadelphia, PA, November 6, 2007.
* Address correspondence to Meredith L. McMorrow, 4770 Buford Highway, NE MS F-22, Atlanta, GA 30341. E-mail: MMcmorrow{at}cdc.gov
Authors’ addresses: Meredith L. McMorrow and S. Patrick Kachur, 4770 Buford Highway, NE MS F-22, Atlanta, GA 30341, Tel: 770-488-7782 (McMorrow) or 770-488-3600 (Kachur), Fax: 770-488-4206, E-mails: MMcmorrow{at}cdc.gov and spk0{at}cdc.gov. M. Irene Masanja, Salim M. K. Abdulla, and Elizeus Kahigwa, Kiko Avenue, Mikocheni P.O. Box 78373, Dar-es-Salaam, Tanzania, Tel: +255-22-277-4714/56, Fax: +255-22-277-1714, E-mails: imasanja{at}excite.com, salim.abdulla{at}gmail.com, and ekahigwa{at}yahoo.com.
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