Validation of a lateral flow assay for the qualitative detection of okadaic acid-group toxins in shellfish

BACKGROUND: Okadaic acid (OA)-group toxins, including OA, dinophysistoxin-1 (DTX1), DTX2, and their acyl esters, cause diarrhetic shellfish poisoning. Regulatory monitoring commonly relies on LC-MS/MS, which is accurate but resource-intensive, creating a need for validated rapid screening methods. OBJECTIVE: To evaluate the Sensoreal DSP Alert™ lateral flow assay (LFA) for qualitative determination of OA-group toxins in bivalve mollusks through single-laboratory validation based on AOAC International and Interstate Shellfish Sanitation Conference guidance. METHODS: The assay was evaluated for probability of detection, sensitivity, false-positive and false-negative rates, ruggedness, and selectivity using mussel and oyster samples across defined toxin concentrations. Naturally contaminated mussels, oysters, scallops, clams, cockles, and razor clams from multiple regions were tested in parallel by LFA and LC-MS/MS. Performance across OA/DTX profiles and semi-quantitative Low/Medium/High interpretation using SensoRead™ test-to-control ratios were also assessed. RESULTS: At 135 µg OA eq/kg threshold (which is 84% of the regulatory limit of 160 µg OA eq/kg), the LFA achieved sensitivity of 1.000, specificity of 0.959, overall agreement of 0.975, and Cohen's kappa of 0.950 in validation samples, with no false negatives. Ruggedness was unaffected by variations in kit lots, reagents, analysts, temperature, incubation time, or testing day. No interference was observed from domoic acid, paralytic shellfish toxins, azaspiracids, microcystins, or tetrodotoxin. Among 180 naturally contaminated samples, sensitivity was 1.000, specificity 0.944, overall agreement 0.972, and kappa 0.944. Performance was not affected by OA/DTX profile variation, and scanner classifications provided useful secondary interpretive information. CONCLUSION: The Sensoreal DSP Alert™ LFA is a robust, sensitive, and user-friendly screening method for qualitative determination of OA-group toxins in bivalve mollusk shellfish. The assay demonstrated excellent agreement with the LC-MS/MS reference method, no false-negative results at the selected decision threshold, reliable ruggedness, and strong selectivity. The scanner-based Low/Medium/High classification provides additional practical value for shellfish hazard management and end-product testing.