THE EVALUATION OF TUBERCULOSIS BY BI-DIGITAL O-RING TEST

Abstract

Background

The rate of incidence of tuberculosis is higher in Japan than in other advanced countries, such as the United States 1) 2). Therefore, is necessary to develop a countermeasure against tuberculosis in Japan. When a tuberculosis patient is discovered, the persons who have been in close contact with that patient are also examined for tuberculosis, in accordance with the law 3). Tuberculin testing is performed on those persons under thirty years of age for the diagnosis of unapparent tuberculosis and when it is determined to be strongly positive, anti-tuberculosis medication is administered to prevent further development of the disease 4). However, this test can sometimes becomes positive in persons who have received Bacillus Calmette-Guerin (BCG) vaccinations, which occurs widely in Japan. The problem with this test is that its specificity is low. Therefore, there is a very high risk that a negative person would be judged positive by this method 5) 6).

Purpose

To examine persons who have undergone tuberculin testing with Bi-Digital O-Ring Test (OMURA, Y. 1977-2006; BDORT), and compare the positive rate of the tuberculin test.

Object

Cases of chest tuberculosis for which the diagnosis was difficult were selected as tuberculosis infection cases. Asymptomatic cases that could be part of a mass outbreak were selected as contact person cases.

Method

Mycobacterium tuberculosis and M. avium were used as reference control substances (RCS) for BDORT. Chest X-rays were measured with BDORT, and compared with the results of the tuberculin test.

Result

The cases of tuberculosis infection were 28-year-old woman and a 68-year-old man. The results of M. tuberculosis by BDORT were 7mg (BDORT Unit) and 16mg (BDORT Unit), respectively. M. avium was less than Ing (BDORT Unit). The contact person cases were 32 men and 22 women, with an average age of 15.6 years.

Tuberculin testing of the contact person cases indicated no negative cases, 40 positive cases and 14 strongly positive cases.

It was determined that prophylactic treatment was necessary for 10 strongly positive cases.

However, according to BDORT, all of the cases exhibited less than Ing of M. tuberculosis and M. avium and the likelihood of tuberculosis infection was low.

[Consideration]

Although the tuberculosis infection level was low, M. tuberculosis was high by BDORT. The QuantiFERON®-TB 2 generation (QFT-2G) test was performed in 10 cases for which prophylactic treatment was considered necessary 7) 8). All of these cases were judged negative, and prophylactic treatment was not administered. This is a new specific blood test for contact cases of tuberculosis, which can overcome the limitations of the tuberculin test; these results corresponded well to that of BDORT.

Conclusion

It is effective to judge chest X-rays with BDORT for the diagnosis of the tuberculosis, and this method can reduce unnecessary prophylactic treatments.