Analysis of Patients with Positive Acid-fast Bacilli Culture and Negative T-SPOT.TB Results.
10.3343/kjlm.2010.30.4.414
- Author:
You Mie HAN
1
;
Hyun Soo KIM
;
Cheol Hong KIM
;
Hee Jung KANG
;
Kyu Man LEE
Author Information
1. Department of Radiology, Hallym University College of Medicine, Seoul, Korea.
- Publication Type:Case Reports ; English Abstract
- Keywords:
Tuberculosis;
Interferon-gamma;
Nontuberculous mycobacteria;
T-SPOT.TB;
False negative
- MeSH:
Adult;
Aged;
Aged, 80 and over;
Bacillus/*isolation & purification;
Culture Media;
Female;
Humans;
Lymphocyte Count;
Lymphopenia/diagnosis/microbiology;
Male;
Polymerase Chain Reaction;
Reagent Kits, Diagnostic;
Sensitivity and Specificity;
Tuberculosis/*diagnosis/microbiology/radiography
- From:The Korean Journal of Laboratory Medicine
2010;30(4):414-419
- CountryRepublic of Korea
- Language:Korean
-
Abstract:
BACKGROUND: T-SPOT.TB is a sensitive test that detects interferon-gamma producing T-cells in tuberculosis patients following stimulation with tuberculosis-specific antigens. Our study was aimed to investigate the possible causes of false negative results of the test by analyzing the patients with positive acid-fast bacilli (AFB) culture and negative T-SPOT.TB results. METHODS: We investigated 138 patients with positive AFB culture results reported between January 2009 and April 2010. Medical records of these patients were reviewed for the results of T-SPOT.TB test, AFB culture, PCR for Mycobacterium tuberculosis (TB-PCR), chest X-ray, drug treatment, etc. Diagnosis of tuberculosis was confirmed by positive TB-PCR or identification of Mycobacterium tuberculosis (MTB). Sensitivity of T-SPOT.TB test was calculated and the possible causes of AFB culture positive and T-SPOT.TB negative results were analyzed. RESULTS: T-SPOT.TB test was performed in 63 of the 138 patients with AFB culture positive results. Fifty-six (88.9%) were positive and 7 patients (11.1%) were negative on T-SPOT.TB test. Of these 7 negative cases, 4 were confirmed as nontuberculous mycobacteria (NTM), 2 were suspected as NTM and diagnosis could not be confirmed in 1. Six of these 7 patients were over 70 yr old and 6 patients had lymphocytopenia. T-SPOT.TB negative results were not observed in any of the 44 patients confirmed to have active tuberculosis (sensitivity 100%). CONCLUSIONS: Our results suggest that T-SPOT.TB test is very sensitive for diagnosing active tuberculosis. NTM may be the main cause of AFB culture positive and T-SPOT.TB negative results, but MTB infection in immunocompromised patients also has to be considered.
