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P137. The usefulness of in vitro interferon-γ assay for differential diagnosis between intestinal tuberculosis and Crohn's disease

D.H. Baek1, G.A. Song1, D.Y. Ryu1, D.U. Kim1, 1Pusan national university hospital, Internal medicine, Busan, South Korea

Background

It is difficult to clinically and endoscopically differentiate intestinal tuberculosis (ITB) and Crohn's disease (CD). The aim of this study was to evaluate the usefulness of in vitro interferon-gamma (IFN-γ) assay for differential diagnosis between ITB and CD.

Methods

Ninety-five patients for whom differential diagnosis between ITB and CD was difficult were enrolled between January 2007 and January 2011. The IFN-γ-producing T-cell response to early secreted antigenic target 6 and culture filtrate protein 10 were measured by T-SPOT.TB blood test in vitro. We evaluated the usefulness of T-SPOT.TB blood test by comparing its results with the final diagnosis.

Results

Forty-five and fifty patients were revealed to be positive and negative in T-SPOT.TB blood test, respectively. Of the 45 patients found to be positive, 31 patients (68.9%) were finally diagnosed as ITB, 11 patients as CD, and 3 patients as Behcet's enterocolitis. Of the 50 patients with negative results, 48 patients (96%) were diagnosed as CD; one as Behcet's enterocolitis; one as nonspecific colitis; none as ITB. The sensitivity and specificity of T-SPOT.TB blood test for ITB were 100% and 78.1%, respectively. Positive and negative predictive values of T-SPOT.TB blood test for ITB were 68.9% and 100%, respectively.

Table 1. Results of T-SPOT.TB blood tests for differential diagnosis between intestinal tuberculosis and other diseases
 TB. ColitisNon-TB. ColitisTotal
Positive311445
Negative 5050
Sensitivity (%)  31/31 (100)
Specificity (%)  50/64 (78.1)
P(+) value (%)  31/45 (68.9)
P(−) value (%)  50/50 (100)
Table 2. Clinical characteristics of intestinal tuberculosis and Crohn's disease
 Intestinal tuberculosis (n = 31)Crohn's disease (n = 59)
Age, years (range)48.1 (26–78)24.1 (17–65)
Male / Female15/1641/18
Symptoms or signs  
 Fever/above 38°10/3 (32%/10%)2/0 (3%/0%)
 Fistula0 (0%)7 (11%)
 Colonoscopic findings0 (0%)14 (23%)
 Ulceration31 (100%)57 (96%)
 Trans./Long./Combine.20/5/6 (64%/16%/20%)11/36/12 (19%/61%/20%)
 Stricture5 (16%)12 (20%)

Conclusion

When differential diagnosis between ITB and CD is difficult, T-SPOT.TB blood test may be a helpful and rapid diagnostic tool to exclude ITB. Prospective large-scaled studies are required for further evaluation of the usefulness of T-SPOT.TB blood test for differential diagnosis between ITB and CD.