Operational application of a rapid antibody-based detection assay for first line screening of paralytic shellfish toxins in shellfish

Paralytic shellfish poisoning toxins (PSP-toxins) are potent neurotoxins associated with marine dinoflagellates and may accumulate in filter-feeding shellfish to cause food intoxication in human. Monitoring programs for PSP in shellfish rely heavily on the use of traditional mouse bioassay (MBA). Considerable progress has been made in developing a reliable, rapid and relatively convenient assay for mass screening of possible PSP contaminated samples. In this study, we investigated the potential application of a commercially available antibody-based assay for routine first line screening of PSP-toxins in shellfish collected in Hong Kong. Preliminary study showed that the Jellett Rapid PSP Test (JRPT) performed acceptably in detecting regulatory limit (80 mu g STXeq per 100 g of shellfish tissue) of each standard toxin under shellfish matrix mediums and human urine, except GTX1,4 and NEO. The results indicated its potential applicability in field and outbreak situations. Upon applying the kits in 938 field samples for over 2 years, no false JRPT-positive result was determined from MBA-positive samples. However, JRPT was able to detect MBA false negative sample that exceeded the regulatory limit as determined by High Performance Liquid Chromatography (HPLC). On the other hand, a number of JRPT false positive results were revealed, based on HPLC data, suggesting that the effective or actual limit of detection for JRPT was less than 40 mu g STXeq per 100 g of shellfish tissue. Of all MBA-JRPT-negative samples, 21% showed HPLC-positive results. Nevertheless, the PSP toxicity levels were below the limit. No false JRPT-negative result was found during the study. This indicated its potential efficacy for use as screening assay from public health perspective. HPLC analysis showed that STX, NEO, GTX2,3 and GTX5 were the most common PSP-toxins found in shellfish. The PSP-toxins profile and their relative abundance in shellfish were demonstrated to be potentially good biochemical markers for investigating and tracing the samples' origin. In addition, 11% of samples were recorded as JRPT-invalid results, in which 78% came from oysters. Treatment of these JRPT-invalid samples by a centrifugation step followed by a centrifugal filtration was very effective (95% validity with clearer indication lines after reanalysis by JRPT) in reducing invalid results through removing potential interfering substance(s) in shellfish matrix. Complementary to MBA and HPLC toxins analysis, JRPT was shown to be an appropriate tool for rapid and mass screening of potential PSP-toxins contaminated shellfish. When public health actions are considered to verify JRPT-positive, HPLC-positive and uncertain cases samples, confirmatory test should be performed by gold method, MBA. (c) 2010 Elsevier B.V. All rights reserved.