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Kim, Kim, Hur, Hyun, Park, Song, Park, Kang, and Lee: Clinical Usefulness of T-SPOT.TB Test for the Diagnosis of Tuberculosis
Original Article

Korean J Leg Med 2010;30(2):171-177.

Published online: 14 January 2010

DOI: https://doi.org/10.3343/kjlm.2010.30.2.171

Clinical Usefulness of T-SPOT.TB Test for the Diagnosis of Tuberculosis

Hyun Soo Kim, M.D.1, Cheol Hong Kim, M.D.2, Mina Hur, M.D.3, In Gyu Hyun, M.D.2, Min Jeong Park, M.D.1, Wonkeun Song, M.D.1, Ji-Young Park, M.D.1, Hee Jung Kang, M.D.1, Kyu Man Lee, M.D.1

1Departments of Laboratory Medicine, Seoul, Korea

2Internal Medicine, Hallym University College of Medicine, Seoul, Korea

3Department of Laboratory Medicine, Konkuk University School of Medicine, Seoul, Korea

Corresponding authors: Hyun Soo Kim, M.D. Department of Laboratory Medicine, Hallym University College of Medicine, 94-200 Yeongdeungpo-dong, Yeongdeungpo-gu, Seoul 150-719, Korea Tel: +82-2-2639-5562, Fax: +82-2-2671-5270 E-mail: hskim0901@empal.com

Cheol Hong Kim, M.D. Department of Internal Medicine, Hallym University College of Medicine, 94-200 Yeongdeungpo-dong, Yeongdeungpo-gu, Seoul 150-719, Korea Tel: +82-2-2639-5412, Fax: +82-2-2677-9756 E-mail: kimch2002@hallym.or.kr

      Revised 25 October 20097 January 2010       Accepted 18 January 2010

Copyright © 2010 Korean Society for Legal Medicine

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background:

Tuberculosis-specific ELISPOT assay (T-SPOT.TB, Oxford Immunotec, UK) is a test that detects interferon-gamma producing T-cells after stimulating patient's lymphocytes with two kinds of tuberculosis-specific antigens (ESAT-6 and CFP-10). We evaluated clinical usefulness of T-SPOT.TB test in Korean adults with intermediate burden of tuberculosis and high rate of BCG vaccination at birth.

Methods:

T-SPOT.TB test was performed in 79 patients and 64 healthy volunteers and these patients and volunteers were classified into four groups: group 1, patients with active tuberculosis (n=30); group 2, patients with not-active tuberculosis (n=27); group 3, patients without tuberculosis (n=24); group 4, healthy volunteers without tuberculosis history (n=62). Positive rates and average spot counts of T-SPOT.TB test were obtained among these groups.

Results:

Positive rates of group 1 (96.4%) and group 2 (92.3%) were higher than those of group 3 (31.6%) and group 4 (27.4%) (P<0.0001). The sensitivity deduced from group 1 and specificity deduced from group 4 of T-SPOT.TB test were 96.4% and 72.6%, respectively. The average spot counts of group 1 and 2 were higher than those of group 3 and 4 (P<0.001). There was a tendency of increasing positive rate with increasing age. Overall agreement between T-SPOT.TB test and tuberculin skin test was 63.8% (kappa=0.29).

Conclusions:

T-SPOT.TB test would be a very useful screening and supplementary test for diagnosis of tuberculosis due to its high sensitivity. However, positive results of T-SPOT.TB should be cautiously interpreted because of high positivity in treated tuberculosis patients and healthy volunteers in Korea.

Keywords: Tuberculosis, Interferon-gamma, ELISPOT

REFERENCES

1.Lee JY., Shim TS. Diagnosis of mycobacterium tuberculosis infection using ex-vivo interferon-gamma assay. Tuberc Respir Dis. 2006. 60:497–509. (이정연및심태선. 체외 Interferon-gamma 검사를이용한결핵감염의진단. 결핵및호흡기질환 2006;60:497-509.).
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Fig. 1.
The number of spot-forming cells of T-SPOT.TB test in the different groups of patients and healthy volunteers.
kjlm-30-171f1.tif
Fig. 2.
Correlation of tuberculin skin test (TST) results with T-SPOT. TB results in patients and healthy volunteers.
kjlm-30-171f2.tif
Table 1.
Grouping of patients and healthy volunteers
Group Characteristics N
Group 1 TB, active patients  
  AFB culture positive 19
  Clinically suspected, anti-TB therapy 11
Group 2 TB, not-active patients Past TB history 14
  Old or stable TB description in radiological report 13
Group 3 Patients without history or evidence of TB 24
Group 4 Healthy volunteers without TB history  
Group 4-1 Hospital workers 36
Group 4-2 Non-hospital workers 26
Total   143

Abbreviations: TB, tuberculosis.

Table 2.
Positive rate and diagnostic validity of T-SPOT.TB test in the different groups of patients and healthy volunteers
Group N Sex (M:F) Age (yr) Mean (SD) T-SPOT.TB positive T-SPOT.TB negative Positive rate
Group 1 28 20:8 54.2 (18.4) 27 1 96.4%
Group 2 26 18:8 56.4 (15.8) 24 2 92.3%
Group 3 19 14:5 60.0 (17.4) 6 13 31.6%
Group 4 62 30:32 30.2 (7.8) 17 45 27.4%
Group 4-1 36 11:25 31.7 (8.6) 13 23 36.1%
Group 4-2 26 19:7 28.1 (5.9) 4 22 15.4%
Total 135 82:53 46.7 (18.2) 74 61 54.8%
Sensitivity deduced from group 1       96.4% (95% CI: 81.6-99.9)    
Sensitivity deduced from group 1 & 2       94.4% (95% CI: 84.6-98.8)    
Specificity deduced from group 3 & 4       71.6% (95% CI: 60.6-81.1)    
Specificity deduced from group 4       72.6% (95% CI: 59.7-83.2)    
Specificity deduced from group 4-2       84.6% (95% CI: 68.8-97.5)    
Group 1, 2, 3, 4: See Table 1.

Abbreviations: SD, standard deviation; CI, confidence interval.

Table 3.
Positive rate of T-SPOT.TB test according to the age
Age N (Total) T-SPOT.TB positive Positive rate N (Group 3,4) T-SPOT.TB positive Positive rate
20-30 44 12 27.3% 40 8 20.0%
31-40 25 12 48.0% 17 4 23.5%
41-50 21 17 81.0% 10 6 60.0%
51-60 14 12 85.7% 5 4 80.0%
61-70 11 10 90.9% 1 0 0.0%
>70 20 11 55.0% 8 1 12.5%
Total 135 74 54.8% 81 23 28.4%
P     <0.0001     0.013

Group 3, 4: See Table 1.

Table 4.
Comparison of T-SPOT.TB test with tuberculin skin test (TST)
  TST (+) TST (-) Total
T-SPOT.TB (+) 29 8 37
T-SPOT.TB (-) 22 24 46
Total 51 32 83
Overall agreement 63.9% (95% CI: 52.6-74.1), kappa=0.29    
PPA 56.9% (95% CI: 43.2-70.7)    
NPA 75.0% (95% CI: 56.6-88.5)    

TST positive: ≥10 mm

Abbreviations: PPA, positive percent agreement; NPA, negative percent agreement; CI, confidence interval.

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