2018 Volume 67 Issue 5 Pages 716-721
The concentration method by centrifugation is recommended for tests of acid-fast bacilli including Mycobacterium tuberculosis. However, the concentration method by centrifugation requires expensive biohazard refrigerated centrifuges. Depending on the circumstances of a facility, it is difficult to introduce it. We conducted a basic study to evaluate the “TB-Beads” method, which is a method of concentrating acid-fast bacilli using magnetic beads and requires no biohazard refrigerated centrifuge. Using 50 sputum specimens for which an acid-fast bacillus test was requested at our facility, we compared acid-fast bacillus tests by both the TB-Beads method and the concentration method by centrifugation. The comparison was carried out in smear tests, culture tests, and genetic tests. The concordance rates of the TB-Beads method with the concentration method by centrifugation were 92.0% in the smear tests, 100% in the culture tests and 98.0% in the genetic tests. In the smear tests, the TB-Beads method was less sensitive than the concentration method by centrifugation, but results of the TB-Beads method and the concentration by centrifugation were in high agreement in the culture tests and the genetic tests. The TB-Beads method can concentrate acid-fast bacilli without using a biohazard refrigerated centrifuge, and thus the accuracy of acid-fast bacillus tests can be improved in more facilities.
