PROFICIENCY SAMPLES FOR QUALITY ASSURANCE IN TRICHINELLA DIGESTION TESTS

A reliable method to produce proficiency samples containing known numb ers of Trichinella spiralis cysts for use in quality assurance systems for Trichinella digestion tests was developed and validated. A filtra te containing Trichinella cysts was produced by homogenizing and filte ring the muscles of an experimentally infected rat. Using a stereomicr oscope and micropipette, intact cysts were removed from the filtrate a nd were transferred onto an agar substrate to allow accurate counting and subsequent transfer into a sample matrix. The proficiency sample m atrix consisted of 20-g balls of lean ground beef and was combined wit h 80 g of a Trichinella-free muscle tissue to obtain the required 100- g sample weight for thr assay. The mean overall larval recovery from 4 04 proficiency samples was 93.0%. Larval recoveries greater than or eq ual to 95, 85, and 75% occurred in 52.4, 84.3, and 94.3%, respectively , of the 404 samples tested. Results indicated that, after a short tra ining period, technicians with no prior experience in digestion techni ques performed as well as experienced technicians. The maximum shelf l ife of proficiency samples was not determined but was at least 3 weeks . Validation data were used to develop panels composed of proficiency samples prepared as described above and to establish guidelines for th e interpretation of proficiency panel results.