Developing a guide for baseline salonella agglutinin titres according to age, gender and HIV status in patients attending at hospitals in northern Namibia.
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Date
2012
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Abstract
In Namibia, the Widal test (a blood test that detects level of Salmonella antibodies) is widely used in the diagnosis of typhoid fever. There are no available normal population baseline Salmonella agglutinins titres in Namibia which can be used to come up with country specific diagnostic titres for typhoid fever. The normal population baseline Salmonella agglutinin titre is used as the basis for the interpretation of the Widal test. Since there is no guide, it means that standardization of patient care in Namibia is not possible. The aim of the study was to develop a guide for the interpretation of diagnostic Salmonella agglutinin titres for typhoid fever after performing a Widal test. The objectives of the study were to; determine the prevalence of typhoid fever for age, gender and HIV status among patients attending five hospitals in northern Namibia; establish age, gender and HIV status presumptively diagnostic Salmonella agglutinin titres for the diagnosis of typhoid fever; develop a conceptual framework based on the outcome of the situational analysis; develop a guide for baseline Salmonella agglutinin titres for age, gender and HIV status in patients attending hospitals in northern Namibia and finally to implement, monitor and evaluate the efficacy of the guide on baseline. Blood samples were collected from 400 subjects; 200 males and 200 females, of the 200 males 100 were children (<16years) and of the 200 females 100 were also children (<16years), half of each gender and age group were HIV positive and the other half HIV negative; the blood samples were examined for the presence and levels of Salmonella antibodies by Widal agglutination technique. Standard S. typhi O and H and Salmonella paratyphi AH and BH suspension (FORTRESS) were used as antigens. This study reports that Typhi O and Typhi H titres greater than 80 are diagnostic of typhoid fever in the studied population regardless of age, gender and HIV status. Typhi O titres greater than 40 and Typhi H titres greater than 80 are diagnostic of typhoid fever in HIV positive patients whilst typhi O titres greater than 80 and typhi H titres greater than 40 are diagnostic of typhoid fever in HIV negative patients. The current diagnostic titre for typhoid fever of 160 for both typhi O and typhi H is too high and many typhoid cases are being missed and must be changed urgently, by the adoption of the guide developed by this study. The current Widal procedure should include a 1 in 120 dilution, to give a titre 120 between titre 80 and titre 160, so as to minimise the risk of missing cases of typhoid fever with titres greater than 80 but less than 160. This study has revealed that the current typhoid diagnostic titre of 160 for both typhi O and H is too high. A guide for the interpretation of Widal test has been developed specifically for northern Namibia. The guide can only be used in patients who are older than 2 years as these are capable of forming antibodies. This study has shown that there is a significant association between HIV and Salmonella agglutinin titres. This revelation could be used to lobby for policy change as in revision of treatment and management of HAART (Highly Active Antiretroviral Therapy) and typhoid vaccination policies. This study has shown that typhoid fever is highly prevalent in Northern Namibia and it calls for drastic public health intervention by all stake holders under the leadership of Ministry of Health and Social Services. Laboratories should implement a comprehensive quality assurance program to enhance the validity and reliability of the Widal test. This will improve accurate diagnosis and give the surest way to reverse the deteriorating health status of Namibians.
Description
A dissertation submitted in fulfilment of the requirements for the Degree of Doctor of Philosophy.
Keywords
Salmonella agglutinin titres