Quantitative Evaluation of Commercially Available Test Kit for Ciguatera in Fish

Abstract

Reliability of the commercially available Cigua-Check^® test kits to identify ciguateric fish was evaluated by assessing the uniformity of conclusions by multiple readers examining identical sticks. One hundred and eighty-eight samples of two types of reef fish were tested for ciguatera using Cigua-Check^® test strips. Paired subsamples of all specimens were also analyzed via the more rigorous N2a neuroblastoma mouse bioassay that is specific for aberration of Na⁺-channel activity that is presumptive for ciguatera fish poisoning. In a double blind trial, four individuals visually examined identical Cigua-Check^® strips to conclude whether the samples were positive or negative for ciguatera. Of the 121 samples that were shown to be positively ciguatoxic via bioassay, the four strip readers were in agreement in concluding positive ciguateric status in 9.9% of the samples; these four readers concluded these positive samples were negative for ciguatera in 26.2% of these bioassay-positive samples. Of the 67 samples that were shown in N2a bioassay to be negatively ciguatoxic, the four readers were in agreement in concluding a negative ciguateric status in 26.9% of the samples; these four strip readers concluded these same samples were positive for ciguatera in 14.9% of these negative samples. The low levels of uniform conclusions among readers examining identical test strips, and the low frequency of agreement with the correct ciguateric status as shown by separate N2a neuroblastoma analyses indicate severe short-comings in the reliability of these test kits to accurately reflect the ciguateric status of samples. The level of uncertainty associated with Cigua-Check^® test kits indicate a continuing need for improvement of a simple, rapid, and reliable means to identify ciguateric fish.