Discussion
Previous investigations have successfully assessed application of DTS for HIV, syphilis, and hepatitis B proficiency testing in resource-limited settings (Mendiratta, 2017, Benzaken, 2014, Ramos, 2013). Experience from many resource-limited countries shows that traditional EQA programs, when they exist, are only limited to national and sometimes regional laboratories without participation from lower tier laboratories. Our intent was to assess stability of DTS as a mean of proficiency testing panels preparation for serological testing of brucellosis to overcome the challenges related to expenses for cold chain maintenance during transportation and storage of liquid samples and biosafety concerns, as it is one of the limiting factors for developing countries.
Taking into consideration One Health approach and the challenges with international EQA in resource-limited settings, we have launched a national EQA survey for serological tests of brucellosis in Armenia simultaneously for both human and veterinary laboratories. At the same time, we have prepared DTS to validate stability to minimize the cost and ensure long term sustainability of national EQA. The most common serological screening tests used are RBT also called bufferedBrucella antigen test (OIE, 2018, Chapter 3.1.4) and serum agglutination test (SAT) which uses serum to detect the presence of agglutinating antibodies to the smooth lipopolysaccharide (S-LPS) or O-polysaccharide (OPS) as a mean of initial diagnosis of Brucella infection, particularly in lower tier laboratories. Secondary confirmatory tests such as CFT, ELISA and/or FPA are recommended as no single serological test is appropriate in all epidemiological situations because all tests have limitations, especially when screening individual animals (OIE, 2018, Chapter 3.1.4). These led us to use these techniques for DTS panel validation.
Results obtained in this study validate the long term (105 days) stability of DTS preparation for brucellosis serological testing. Therefore, the implementation of the novel approach described in this study provides a simple solution for organization of brucellosis serological EQA programs in resource-limited settings. The same strategy could also be used to prepare laboratory internal quality control specimens at national level that could be then distributed to the regional and district laboratories. Moreover, this method could also be implemented in countries experiencing challenges of storage, cold chain maintenance, and timely transport of brucellosis clinical samples from remote areas, point-of-care or lower tier laboratories to the central level for diagnosis or conformational purposes. Thus, the brucellosis DTS method has several advantages over traditional methods: 1) it is easy and cheap to prepare, 2) it is safer and less biohazardous (no spills risk during transportation), 3) the specimens could be transported and stored at room temperature without the need for maintaining expensive cold chain, and 4) as demonstrated here, to have stability over a long period of time.
In conclusion, brucellosis DTS maintain integrity of serum samples for serological testing of brucellosis for the indicated period and can be a powerful tool for EQA providers, as it decreases shipping costs and avoids challenges of maintaining cold chain shipments between the provider and recipient laboratories. Moreover, within One Health context, dried tube specimens have great prospect to enable EQA programs to reinforce veterinary and human laboratories collaboration. The utility of this tool also includes increasing coverage of EQA to the lower tier labs in resource-limited countries, with minimal costs to monitor and improve the quality and accuracy of brucellosis testing for veterinary and human laboratories.