Evaluation of antigen-detecting and antibody-detecting diagnostic test combinations for diagnosing melioidosis

Abstract

Background Melioidosis, an infectious disease caused by Burkholderia pseudomallei, is endemic in many tropical developing countries and has a high mortality. Here we evaluated combinations of a lateral flow immunoassay (LFI) detecting B. pseudomallei capsular polysaccharide (CPS) and enzyme-linked immunosorbent assays (ELISA) detecting antibodies against hemolysin co-regulated protein (Hcp1) or O-polysaccharide (OPS) for diagnosing melioidosis. Methodology/Principal findings We conducted a cohort-based case-control study. Both cases and controls were derived from a prospective observational study of patients presenting with community-acquired infections and sepsis in northeast Thailand (Ubon-sepsis). Cases included 192 patients with a clinical specimen culture positive for B. pseudomallei. Controls included 502 patients who were blood culture positive for Staphylococcus aureus, Escherichia coli or Klebsiella pneumoniae or were polymerase chain reaction assay positive for malaria or dengue. Serum samples collected within 24 hours of admission were stored and tested using a CPS-LFI, Hcp1-ELISA and OPS-ELISA. When assessing diagnostic tests in combination, results were considered positive if either test was positive. We selected ELISA cut-offs corresponding to a specificity of 95%. Using a positive cut-off OD of 2.912 for Hcp1-ELISA, the combination of the CPS-LFI and Hcp1-ELISA had a sensitivity of 67.7% (130/192 case patients) and a specificity of 95.0% (477/502 control patients). The sensitivity of the combination (67.7%) was higher than that of the CPS-LFI alone (31.3%, p<0.001) and that of Hcp1-ELISA alone (53.6%, p<0.001). A similar phenomenon was also observed for the combination of CPS-LFI and OPS-ELISA. In case patients, positivity of the CPS-LFI was associated with a short duration of symptoms, high modified Sequential (sepsis-related) Organ Failure Assessment (SOFA) score, bacteraemia and mortality outcome, while positivity of Hcp1-ELISA was associated with a longer duration of symptoms, low modified SOFA score, non-bacteraemia and survival outcome. Conclusions/Significance A combination of antigen-antibody diagnostic tests increased the sensitivity of melioidosis diagnosis over individual tests while preserving high specificity. Point-of-care tests for melioidosis based on the use of combination assays should be further developed and evaluated.

What is the Role of Lateral Flow Immunoassay for the Diagnosis of Melioidosis?

“…Our results confirm previous findings from Thailand that the sensitivity of serum/plasma using AMD increases substantially with severity of illness [ 9 , 15 ]. This predominantly reflects the B. pseudomallei bacterial load in the bloodstream, but conceivably also higher tissue burdens of infection such as multiple lung and organ abscesses, with CPS likely to be shed into the bloodstream.…”

“…In our study, AMD on serum was positive in only 13% of those who were blood culture negative, 39% of those who were blood culture positive, and 68% of those with melioidosis septic shock. Similar results from serum have been found in Thailand, with 7% and 38% AMD positive in those who were blood culture negative and positive, respectively [ 15 ]. In another study from Australia, AMD sensitivity on EDTA whole blood from 45 bacteremic melioidosis samples was 40% [ 8 ], but in a study from Laos only 14% of sera from bacteremic melioidosis patients were AMD positive [ 10 ].…”

“…The variety of clinical samples tested and analyses performed make direct comparisons between the study results problematic, but consistent themes emerged. First, the sensitivity on whole blood, serum, and plasma was very low overall and <50% even in bacteremic melioidosis but did increase in severe disease with presumed higher bacterial burden [ 9 , 15 ]. Second, sensitivity was higher in sputum from those with melioidosis pneumonia and was mostly excellent in pus and fluids aspirated from abscesses in patients with melioidosis.…”

Sensitivity and specificity of DPP® Fever Panel II Asia in the diagnosis of malaria, dengue and melioidosis

“…Second, there is the potential use of population-specific cutoffs to achieve particular objectives, such as maintaining sufficiently high specificity to ensure clinical utility. Finally, at the patient level quantitative readouts for some antigens could also act as markers of severity, as has been shown for HRPII in malaria [16], for CPS in melioidosis [17] and in some studies for NS1 in dengue [18]. Chembio Diagnostic, Inc., in collaboration with Foundation for Innovative New Diagnostics (FIND), developed a multiplex lateral flow immunoassay (DPP® Fever Panel II Assay) that is able to detect serum immunoglobulin M (IgM) and specific microbial antigens of the most common agents of acute febrile illness (AFI) in Asia.…”

Normalizing the Optical Signal Enables Robust Assays with Lateral Flow Biosensors

“… 1 − 3 Such advantages have promoted the development of rapid assay kits with applications in disease diagnostics, food surveillance, drug testing, and environment monitoring. 4 − 8 Most LFAs generate optical signal when their detection targets are present. The signal can be conveniently detected via visual inspection (e.g., naked eyes), although the interpretation is qualitative (yes/no) and can be ambiguous at low-target concentrations.…”