A Rapid Immunochromatography Test Based on Hcp1 Is a Potential Point-of-Care Test for Serological Diagnosis of Melioidosis

Abstract

Melioidosis is a fatal infectious disease caused by the environmental bacterium Burkholderia pseudomallei It is highly endemic in Asia and northern Australia but neglected in many other tropical countries. Melioidosis patients have a wide range of clinical manifestations, and definitive diagnosis requires bacterial culture, which can be time-consuming. A reliable rapid serological tool is greatly needed for disease surveillance and diagnosis. We previously demonstrated by enzyme-linked immunosorbent assay (ELISA) that a hemolysin-coregulated protein (Hcp1) is a promising target for serodiagnosis of melioidosis. In this study, we developed a rapid immunochromatography test (ICT) using Hcp1 as the target antigen (Hcp1-ICT). We evaluated this test for specific antibody detection using serum samples obtained from 4 groups of human subjects, including the following: (i) 487 culture-confirmed melioidosis patients from four hospitals in northeast Thailand; (ii) 202 healthy donors from northeast Thailand; (iii) 90 U.S. healthy donors; and (iv) 207 patients infected with other organisms. Compared to culture results as a gold standard, the sensitivity of ICT for all hospitals was 88.3%. The specificities for Thai donors and U.S. donors were 86.1% and 100%, respectively, and the specificity for other infections was 91.8%. The results of the Hcp1-ICT demonstrated 92.4% agreement with the Hcp1-ELISA results with a kappa value of 0.829, indicating that the method is much improved compared with the current serological method, the indirect hemagglutination assay (IHA) (69.5% sensitivity and 67.6% specificity for Thais). The Hcp1-ICT represents a potential point-of-care (POC) test and may be used to replace the IHA for screening of melioidosis in hospitals as well as in resource-limited areas.

Keywords: Burkholderia pseudomallei; antibody detection; immunochromatography test; melioidosis; point-of-care test; rapid test; serological diagnosis.

FIG 1

Immunochromatography test (ICT) procedure. A serum sample (10 μl) from a suspected melioidosis patient is applied to the sample well followed by addition of four drops (120 μl) of running buffer to the sample well. The test was allowed to process the sample for 15 min before the result was read. The result was evaluated by the presence of a control line with either a visible or nonvisible test line. The presence of a red line at the test line was interpreted as representing a positive result, while the absence of a red line at the test line was interpreted as representing a negative result.

FIG 2

Comparison of results of Hcp1-ICT and Hcp1-ELISA with different OD values.