Clinical Usefulness of An Immunochromatographic Assay Based on 38 kDa Antigen for The Diagnosis of Active Tuberculosis

Kim, Moon Yeun; Ha, Gyoung Yim; Jung, Dong Gil; Song, Kyung Eun; Suh, Jang Soo; Lee, Won Kil; Kim, Jay Sik; Kim, Jae Ryong

Abstract

BACKGROUND
To detect active tuberculosis, clinicians usually rely on several methods those are so limited. As the prevalence rate of tuberculosis is high in Korea, culture is not so very effective in clinical use. The polymerase chain reaction (PCR) featuring rapidness and high sensitivity offers low specificity and it requires high test cost, complicated skills, expensive equipment. This study attempted to determine if the immunochromatographic assay, intended to measure antibodies using 38 kDa antigens, is valuable as a new method to diagnose active tuberculosis, by comparing it with existing acid-fast stain (AFB stain) and PCR.
METHODS
The sera were collected from 31 BCG-vaccinated healthy persons and 55 patients subjected to AFB stain and PCR who visited Pohang Hospital of Dongguk University or Kyungpook National University Hospital, and then kept at -20degrees C until experiment. Fifty-five patients subjected to AFB stain and PCR were composed of 24 active tuberculosis patients and 31 non-TB patients. The evaluation of active tuberculosis was based on clinical criteria.
RESULTS
The detection rate of antibody by the immunochromatographic method accounted for 83% in the active TB group, and each 6% in both the non-TB group and the healthy control group. The sensitivities of AFB stain, PCR and immunochromatographic method accounted for 67%, 88% and 83%, respectively, the specificities for 94%, 86% and 94%, respectively, the positive predictive values for 89%, 84% and 91%, respectively, and the negative predictive values for 78%, 89% and 88%, respectively.
CONCLUSIONS
This suggests that the immunochromatographic method can be used for the rapid diagnostic method of active tuberculosis in an area with high prevalence value of tuberculosis like Korea. In addition, the immunochromatographic method showed the sensitivity approximate to that of PCR, the same specificity as AFB stain, and a high positive and negative predictive values. So it was expected not only to be greatly helpful for the diagnosis of active tuberculosis but also to be more useful in clinical practices because of short examination time, no special equipment and skills required, and inexpensive examination.