Comparison of Melioidosis Indirect Hemagglutination Assay between Three Testing Laboratories in Australia.

Melioidosis caused by Burkholderia pseudomallei causes significant morbidity and mortality in Southeast Asia and northern Australia. Clinical manifestations remain diverse, including localized skin infection, pneumonia, and chronic abscess formation. Culture remains the gold standard of diagnosis, with serology and antigen detection tests playing a role if culture is unfeasible. Serologic diagnosis remains challenging, with limited standardization across different assays. In areas of endemicity, high rates of seropositivity have been documented. The indirect hemagglutination assay (IHA) is one of the more widely used serologic tests in these areas. In Australia, only three centers perform the test. Annually, laboratory A, laboratory B, and laboratory C perform approximately 1,000, 4,500, and 500 tests, respectively. A comparison of a total of 132 sera was analyzed from the routine quality exchange program between these centers from 2010 until 2019. Overall, 18.9% of sera tested had an interpretative discrepancy between laboratories. This study found significant discrepant results between three Australian centers offering the melioidosis indirect hemagglutination assay (IHA), despite testing the same samples. We have highlighted that the IHA is a nonstandardized test, which had different source antigens at each of the different laboratories. Melioidosis is a global disease, is associated with significant mortality, and is perhaps under recognized. It is likely to have increasing impact with changing weather patterns. The IHA has been used frequently as an adjunct to the diagnosis of clinical disease and is the mainstay of determining seroprevalence within populations. Despite its relative ease of use, especially in low resource settings, our study highlights the significant limitations of the melioidosis IHA. It has wide ranging implications, serving as an impetus for developing better diagnostic tests. This study is of interest to practitioners and researchers working in the various geographic regions affected by melioidosis.