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Evaluation of a Rapid Test for the Diagnosis of Cholera in the Absence of a Gold StandardPage, Anne-Laure; Alberti, Kathryn P.; Mondonge, Vital; Rauzier, Jean; Quilici, Marie-Laure; Guerin, Philippe J.; Bhutta, Zulfiqar A.; Epicentre, Paris, France; Ministry of Health, Kinshasa, Democratic Republic of Congo; Institut Pasteur, Unité des Bactéries Pathogènes Entériques, Centre National de Référence des Vibrions et du Choléra, Paris, France; Nuffield Department of Clinical Medicine, Centre for Tropical Medicine, Centre for Clinical Vaccinology and Tropical Medicine (CCVTM), University of Oxford, Oxford, United Kingdom (Public Library of Science, 2012-05-30)Early detection and confirmation of cholera outbreaks are crucial for rapid implementation of control measures. Because cholera frequently affects regions with limited laboratory resources, rapid diagnostic tests (RDT) designed for field conditions are important to enhance rapid response. Stool culture remains the ‘‘gold standard’’ for cholera diagnosis; however, its lack of sensitivity may lead to underestimation of test specificity. We evaluated the Crystal VCH immunochromatographic test (Span Diagnostics, India) for cholera diagnosis using a modified reference standard that combines culture-dependent and independent assays, or a Bayesian latent class model (LCM) analysis. The study was conducted during a cholera epidemic in 2008, in Lubumbashi, Democratic Republic of Congo. Stools collected from 296 patients were used to perform the RDT on site and sent to Institut Pasteur, Paris, for bacterial culture. In comparison with culture as the gold standard, the RDT showed good sensitivity (92.2%; 95% CI: 86.8%–95.9%) but poor specificity when used by a trained laboratory technician (70.6%; 95% CI: 60.7%–79.2%) or by clinicians with no specific test training (60.4%, 95% CI: 50.2%–70.0%). The specificity of the test performed by the laboratory technician increased to 88.6% (95% CI: 78.7–94.9) when PCR was combined with culture results as the reference standard, and to 85.0% (95% CI: 70.4–99.2), when the Bayesian LCM analysis was used for performance evaluation. In both cases, the sensitivity remained high. Using an improved reference standard or appropriate statistical methods for diagnostic test evaluations in the absence of a gold standard, we report better performance of the Crystal VCH RDT than previously published. Our results confirm that this test can be used for early outbreak detection or epidemiological surveillance, key components of efficient global cholera control. Our analysis also highlights the importance of improving evaluations of RDT when no reliable gold standard is available.
Use of a Cholera Rapid Diagnostic Test during a Mass Vaccination Campaign in Response to an Epidemic in Guinea, 2012Martinez-Pino, Isabel; Luquero, Francisco J; Sakoba, Kéïta; Sylla, Souleymane; Haile, Melatwork; Grais, RFebecca F; Ciglenecki, Iza; Quilici, Marie-Laure; Page, Anne-Laure; European Programme for Intervention Epidemiology Training (EPIET), European Centre for Disease Prevention and Control (ECDC), Stockholm, Sweden ; Epicentre, Paris, France. (Public Library of Science, 2013-08-15)During the 2012 cholera outbreak in the Republic of Guinea, the Ministry of Health, supported by Médecins Sans Frontières - Operational Center Geneva, used the oral cholera vaccine Shanchol as a part of the emergency response. The rapid diagnostic test (RDT) Crystal VC, widely used during outbreaks, detects lipopolysaccharide antigens of Vibrio cholerae O1 and O139, both included in Shanchol. In the context of reactive use of a whole-cell cholera vaccine in a region where cholera cases have been reported, it is essential to know what proportion of vaccinated individuals would be reactive to the RDT and for how long after vaccination.