Comparison of a modified digestion assay with trichinoscopy for the detection of Trichinella larvae in pork.

A pepsin-HCl digestion assay and two compressorium techniques (trichinoscopy) for the identification of swine muscle tissue containing low levels of Trichinella larvae were compared as part of the test validation process for quality assurance purposes. Compressoria read with a stereomicroscope detected more larvae (P < 0.0001, n = 57) and more tissues (P = 0.0047, n = 57) than did compressoria read with a projection microscope (trichinoscope). The digestion assay evaluated was 3.2 times as likely as the best compressorium technique to identify a positive tissue when these procedures were used to test 1 g of infected muscle (P < 0.001; 95% confidence interval for the odds ratio, 2.0 to 5.4; n = 161 and n = 189, respectively). Detection by trichinoscopy improved as the number of larvae in tissues increased to > 2 larvae per g, but trichinoscopy was less sensitive than the digestion assay regardless of the tissue larval load. These data indicate that the quality controlled digestion assay used in this study is more sensitive than trichinoscopic techniques in the detection of tissues containing low levels of Trichinella larvae.