Comparison study of three rapid test kits for histamine in fish: BiooScientific MaxSignal enzymatic assay, Neogen Veratox ELISA, and the Neogen Reveal Histamine Screening test

Two new test kits for quantifying histamine in fish are investigated and compared to the Neogen Veratox ELISA. One of the kits is based on selective enzymatic conversion of histamine by histamine dehydrogenase (MaxSignal, B100 Scientific, Austin, Texas) and the other is dipstick based on lateral flow immuno-chromatography (LFIC). These new kits are compared to Veratox using spiked and naturally contaminated fresh and frozen yellowfin tuna and mahi mahi, as well as canned mackerel in broth and canned tuna in oil and in broth. Histamine levels determined using the MaxSignal enzymatic kit in spiked and naturally contaminated fish were strongly correlated with levels detected with the Veratox ELISA. Comparing both new kits and also using the AOAC performance tested Veratox, spiking at 0 and 50 mg/kg, no false negatives or false positives were found over a wide range of concentrations of histamine. In contrast to competitive ELISA kits, which give a sigmoidal (logistics curve) color response that decreases with increasing analyte, the enzymatic kit gives a linear response, increasing with histamine concentration. Linearity is excellent and samples can be analyzed without further dilution using the included standards to quantify up to 70 mg/kg histamine free base. The 450 nm endpoint color develops rapidly, and using a reaction time of 30 min, recoveries in canned tuna and mackerel were greater than 90% and apparent histamine levels reach a plateau versus time. In contrast, recoveries using the manufacturer's recommended reaction time of 10 min were low, and further study supported the presence of naturally occurring inhibitors of histamine dehydrogenase in fish. Using an extended (30 min) reaction time, the enzymatic kit performed well and was still rapid. The simplicity of the procedure results in a kit more easily mastered and potentially more rugged than competitive ELISA assays, which require multiple incubations, a wash step, additional dilution steps, and twice as many pipetting steps. The LFIC kit Reveal was also found to be simpler and easier to use than ELISA kits, having only one critical pipetting step, requiring no acylation, and only minimal sample manipulation. If accelerated sample removal and grinding could be implemented and validated, the LFIC kit Reveal appears to have excellent potential for onsite testing. Published by Elsevier Ltd.