Helmintex is the reference method to compare performance to others, says, Dr. Carlos Graeff-Teixeira
Brazilian study shows Helmintex method has a high sensitivity to detect Schistosoma mansoni eggs and performance failure in fast urine antigen detection test07/05/2018
The study recently published on PLoS Neglected Tropical Diseases journal, entitled Study of diagnostic accuracy of Helmintex, Kato-Katz and POC-CCA methods for diagnosing intestinal schistosomiasis in Candeal, a low intensity transmission area in northeastern Brazil revealed two main findings: first, the confirmation of Helmintex methods high sensitivity to detect Schistosoma mansoni eggs; second, the performance failure of rapid urine antigen detection (POC-CCA), especially when the egg load in the feces was lower. According to Infectious and Parasitic Diseases MSc. and Tropical Diseases PhD, Carlos Graeff-Teixeira, one of the authors, the study explains one of Helmintexs main role: to serve as a reference method, to compare the performance of other methods.
The researcher explains the fundamental difference between Helmintex method and Kato-Katz (KK) test is the amount of examined feces. KK examines 50 milligrams, while HTX examines 30 grams. This is the main reason for HTXs greater sensitivity. Although very sensitive, HTX is more work consuming and expensive, if compared to KK, which is very simple and cheap. Therefore, in the current stage, HTX is not a method to be used on a routine basis for diagnostic, but in researches, especially for performance comparison with other methods, he says.
Control initiatives have successfully reduced schistosomiasis prevalence and transmission intensity in several places throughout the world. However, individuals who release a smaller number of eggs in the feces may not be detected by classic methods, which are limited due to the low sensitivity. According to Dr. Graeff-Teixeira, this happens because control measures cannot cease the problem, but reduce its intensity, and people will not infect themselves as repeatedly as before, remaining with few worms that produce few eggs. Fast urine antigen detection tests are among the most promising for field work. Like pregnancy tests, when a drop of urine is shed in a plastic supports orifice and the result is the appearance or not of a line, visible to the naked eye. The antigen in the urine is detected by an especially prepared membrane, he says. According to the researcher, only now it will be possible to adequately assess this and other tests (serology, PCR), since the HTx is an excellent reference method, or gold-standard. Dr. Still adds that results from the work performed in Southern Sergipe evidenced the need to enhance the POC-CCA or equivalent method.
Dr. Graeff-Teixeira said that additional improvements to make Helmintex less labor intensive are under field tests. Helmintex has an initial phase somewhat like feces rinse and reject, by several procedures, called concentration phase. During this phase, the volume of analyzed feces is reduced form 30 grams to approximately half gram. The idea is to make isolation by residue size difference in a closed, cleaner and faster system. A cooperation with two Australian universities, Queensland and West Australia, also developed a probe able to generate powerful magnetic micro-gradient, to increase the egg isolation effectiveness. The final phase, which is to detect or identify the eggs, several alternatives are under studies, among which, radiant energy emission induction by egg surface, what could dismiss the time consuming microscope examination, he says.
Planning of public policies to eliminate parasitic diseases as a public health problem in Brazil
In some tropical countries, as Brazil, schistosomiasis control programs lead to considerable prevalence and parasite load among endemic populations. Asked about the current schistosomiasis and helminthic infections in Brazil, Dr. Graeff-Teixeira recalls that the Ministry of Healths Surveillance Secretary coordinated a national inquiry that revealed an important reduction in the number of intestinal parasitic diseases. The numbers from the MoH also showed a decrease of several classic forms, as liver and spleen impairment in the entire country. So the situation, in general, as well as the populations living standards, have relatively enhanced. At the same time, the potential for schistosomiasis to expand from its occurrence area was significantly increased by eco-tourism activities, he pointed.
To the specialist, public policies must be State policies, planned and pursued throughout long periods far beyond the short government terms. To him, from a practical standpoint, technical staff careers must be valued and uncoupled from passing political-partisan situations. Parasitic diseases, in general, and particularly schistosomiasis, will be eliminated when three capital problems are solved: better income distribution along with and full citizenship-aimed education and the effective equality ensuring the most fundamental rights to all Brazilians, he asserts.…