Evaluation of diagnostic methods for the detection of intestinal schistosomiasis in endemic areas with low parasite loads: Saline gradient, Helmintex, Kato-Katz and rapid urine test
| Autor: | Vanessa Normandio de Castro, Vivian Favero, Deborah Negrão-Corrêa, Frederico F. Gil, Catieli Gobetti Lindholz, Áureo Almeida de Oliveira, Andressa Mariana Saldanha Elias, Mariângela Carneiro, Maria Aparecida Gomes, Stefan M. Geiger, Paulo Marcos Zech Coelho, Fernando Sérgio Barbosa, Warllem Junio Oliveira, Fernanda do Carmo Magalhães, Martin Johannes Enk, Carlos Graeff-Teixeira |
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| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
Male
0301 basic medicine Veterinary medicine Schistosoma Mansoni Physiology Urine Parasite load Parasite Load Feces 0302 clinical medicine fluids and secretions Prevalence Medicine and Health Sciences Parasite Egg Count Schistosomiasis Medicine Child Aged 80 and over biology Esquistossomose mansoni / parasitologia lcsh:Public aspects of medicine Neglected Diseases Eukaryota Middle Aged Biologia Celular Body Fluids Infectious Diseases Helminth Infections Child Preschool Income Schistosoma Female Schistosoma mansoni Anatomy Brazil Research Article Neglected Tropical Diseases Adult lcsh:Arctic medicine. Tropical medicine Adolescent lcsh:RC955-962 Point-of-Care Systems Concordance 030231 tropical medicine Intestinal Schistosomiasis Sensitivity and Specificity Young Adult 03 medical and health sciences Water Supply Helminths parasitic diseases Parasitic Diseases Animals Humans Aged Protozoan Infections Clinical Laboratory Techniques business.industry Urina / parasitologia Organisms Public Health Environmental and Occupational Health Biology and Life Sciences lcsh:RA1-1270 Tropical Diseases biology.organism_classification medicine.disease Invertebrates Schistosomiasis mansoni 030104 developmental biology T?cnicas e Procedimentos Diagn?sticos Socioeconomic Factors Parasitology Antigens Helminth Parasitic Intestinal Diseases business |
| Zdroj: | Repositório Digital do Instituto Evandro Chagas (Patuá) Instituto Evandro Chagas (IEC) instacron:IEC PLoS Neglected Tropical Diseases, Vol 12, Iss 2, p e0006232 (2018) PLoS Neglected Tropical Diseases |
| Popis: | Background In some tropical countries, such as Brazil, schistosomiasis control programs have led to a significant reduction in the prevalence and parasite burden of endemic populations. In this setting, the Kato-Katz technique, as the standard diagnostic method for the diagnosis of Schistosoma mansoni infections, which involves the analysis of two slides from one fecal sample, loses its sensitivity. As a result, a significant number of infected individuals are not detected. The objective of this study was to perform extensive parasitological testing of up to three fecal samples and include a rapid urine test (POC-CCA) in a moderate prevalence area in Northern Minas Gerais, Brazil, and evaluate the performance of each test separately and in combination. Methods and findings A total of 254 individuals were examined with variants of the standard Kato-Katz technique (up to18 Kato-Katz slides prepared from three fecal samples), a modified Helmintex (30 g of feces), the saline gradient (500 mg of feces), and the POC-CCA methods. We established a reference standard taking into consideration all the positive results in any of the parasitological exams. Evaluation of the parasite burden by two Kato-Katz slides confirmed that most of the individuals harbored a light infection. When additional slides and different parasitological methods were included, the estimated prevalence rose 2.3 times, from 20.4% to 45.9%. The best sensitivity was obtained with the Helmintex method (84%). All parasitological methods readily detected a high or moderate intensity of infection; however, all lost their high sensitivity in the case of low or very low intensity infections. The overall sensitivity of POC-CCA (64.9%) was similar to the six Kato-Katz slides from three fecal samples. However, POC-CCA showed low concordance (κ = 0.34) when compared with the reference standard. Conclusions The recommended Kato-Katz method largely underestimated the prevalence of S. mansoni infection. Because the best performance was achieved with a modified Helmintex method, this technique might serve as a more precise reference standard. An extended number of Kato-Katz slides in combination with other parasitological methods or with POC-CCA was able to detect more than 80% of egg-positive individuals; however, the rapid urine test (POC-CCA) produced a considerable percentage of false positive results. Author summary Human infection with the flatworm Schistosoma mansoni continues to be a public health problem in many tropical countries, including Brazil. The parasitological method recommended by the World Health Organization for the detection of intestinal schistosomiasis, the Kato-Katz method (KK), underestimates the prevalence of the infection in endemic areas with reduced parasite burden. When extensive and supplementary parasitological exams were performed, the prevalence of schistosomiasis in the examined population increased 2.3 times. Additional KK slides and other parasitological methods, such as saline gradient and Helmintex, allowed us to establish a strong reference standard that was used to assess the parasitological tests and the rapid urine test for the detection of the circulating cathodic antigen of S. mansoni (POC-CCA). All tests readily detected the presence of the flatworm in individuals with medium to high parasite loads. The Helmintex method showed the best performance as it detected almost 84% of all infected individuals. A variant of the standard KK method, involving six fecal smears from three stool samples, detected two-thirds of all infections, thus having a performance comparable to that found with the POC-CCA. A combination of this variant KK method with the POC-CCA may be a field-applicable alternative to improve the diagnosis of S. mansoni infections in individuals with low parasite loads in endemic areas. |
| Databáze: | OpenAIRE |
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