. "Factors Causing Difficulties in Uniformity of Results Among Testing Facilities in Microbiologic Monitoring of Laboratory Animals." Microbial Status and Genetic Evaluation of Mice and Rats: Proceedings of the 1999 US/Japan Conference. Washington, DC: The National Academies Press, 2000.
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Microbial Status and Genetic Evaluation of Mice and Rats: PROCEEDINGS OF THE 1999 US/JAPAN CONFERENCE
antibody positive. All animal experiments were immediately stopped and the animals destroyed. Later we were asked to test the samples, and the results were negative. Testing was performed using basically the same method except for a slight modification to inhibit nonspecific reactions; however, the results were different.
The results in the testing facility of the university were considered positive at an antibody titer of 1:16. They took the position of stating only that there was a positive reaction and deferring to the client to decide whether there was an infection, even though they were experts in this field. When we obtained results showing that antibody titers were in the 1:20 to 1:100 range (so-called low antibody titer) in the IFA test, we reported these results to the client while continuing the testing process. Inasmuch as there was little possibility of real infection, we collected blood samples after 1 week for retesting because generally in contaminated facilities, both the prevalence and antibody titer increase when retesting is performed. We have performed Hantavirus antibody tests on several thousand samples a year and have found only about 10 samples showing such low antibody titers. However, these samples were all found to be negative using immunoblot analysis.
The discrepancy between our test results and those of the university appeared to be caused by differences in the basic position of the testing facility when submitting the test results to the client. There are two different positions: One is simply to hand over the test results, and the other is to consider countermeasures after obtaining the results and assuring highly accurate test results. We naturally take the latter position.
The reasons for discrepancies in culture results include difficulty in accurate identification of isolates and differences in sample collection sites and tests for identification of bacteria. For the several test methods available in antibody tests, it is necessary to confirm the advantages and disadvantages of each method and select the method based on an overall evaluation of the factors. The position taken by the testing facility concerning its level of responsibility when submitting test results will also influence the results.
I am well aware that test methods are in a constant state of development, test facilities take pride in their techniques, and it is very difficult to achieve uniform test methods. I want to stress that simply listing the test items is not sufficient for international harmonization of microbiologic testing of laboratory animals. The test items must include the test method as well as a recommendation of usefulness. Even when there are no major differences in test methods, there are cases in which different results are presented to the client. These differences probably depend on the philosophy adopted by each testing facility.