Acta Oto-Laryngologica. 2013; Early Online, 1–4
ORIGINAL ARTICLE
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Interferon-g release assay in the diagnosis of laryngeal tuberculosis
BING FEI*1,2, ZHENG WU*3, KEHUA MIN2, JINGBO ZHANG2, CHUANLIAN DING2 & HAO WU1 1
Department of Otolaryngology-Head and Neck Surgery, Affiliated Hospital of Nantong University, Nantong, Jiangsu, PR China, 2Department of Otolaryngology, Jin Hu People’s Hospital, Huai An, Jiangsu, PR China and 3Department of Otolaryngology, Chang Shu Second People’s Hospital, Su Zhou, Jiangsu, PR China
Abstract Conclusion: The T-SPOT test for Mycobacterium tuberculosis infection (T-SPOT.TB) can be used for early diagnosis of laryngeal tuberculosis (TB). Objective: The incidence of TB is increasing on a global scale. Laryngeal TB is the most common extrapulmonary form of TB and its early diagnosis is still difficult. This study investigated the performance of the interferon-g release assay in the diagnosis of laryngeal TB. Methods: A total of 83 patients with laryngeal neoplasms were confirmed to have laryngeal TB by pathology, acid-fast staining, and/or fluorescence quantitative PCR. In addition, 52 patients with vocal cord polyps were enrolled as the control group. Two groups underwent both T-SPOT.TB and tuberculin skin test (TST). Results: T-SPOT.TB was positive in 75 cases in the laryngeal TB group and 4 cases in the control group, showing a sensitivity of 90.3% (75/83) and a specificity of 92.3% (48/52). The TST was positive in 42 cases and 20 cases, respectively, in these two groups. Obviously, TST and T-SPOT.TB were significantly different in terms of sensitivity when applied for detection of laryngeal TB (p < 0.05).
Keywords: T-SPOT.TB, tuberculin skin test, diagnosis, specificity
Introduction Worldwide, tuberculosis (TB) remains one of the most important infectious causes of mortality. In 2010, there were an estimated 8.8 million incident cases and approximately 1.4 million people died from this disease [1]. A vast pool of individuals with latent TB infection (LTBI) persists in developing countries, posing a major barrier to global TB control [2]. China is among the 22 countries with the heaviest TB burdens and has the second largest TB population in the world. There are about 0.55 billion people infected, which is a much higher infection rate than the global rate of 1/3 of the population all over the world have infected TB [3]. The prevalence of TB has increased for a variety of reasons including the overuse of antibiotics, mutation of Mycobacterium tuberculosis, antibiotic resistance, diabetes mellitus,
and AIDS and other immunodeficiency disorders [4]. Laryngeal TB is the most common type of extrapulmonary TB and varies greatly in disease onset and signs and symptoms, leading to a high rate of misdiagnosis [5]. The T-SPOT test for Mycobacterium tuberculosis infection (T-SPOT.TB) has been widely used in the diagnosis of pulmonary TB, but its application in the diagnosis of laryngeal TB has not been reported. In this study, we investigated the performance of T-SPOT.TB in the diagnosis of laryngeal TB. Materials and methods Patients A total of 83 patients (46 men and 37 women; age, 30–65 years; mean, 47.1 years) were found to have
Correspondence: Professor Hao Wu, Department of Otolaryngology-Head and Neck Surgery, Affiliated Hospital of Nantong University, Nantong, Jiangsu Province, 226001, People’s Republic of China. Tel: +86 13706294560. E-mail: [email protected] *These authors contributed equally to this work.
(Received 22 July 2013; accepted 21 September 2013) ISSN 0001-6489 print/ISSN 1651-2251 online 2013 Informa Healthcare DOI: 10.3109/00016489.2013.850174
Acta Otolaryngol Downloaded from informahealthcare.com by Universitaets- und Landesbibliothek Duesseldorf on 01/03/14 For personal use only.
2
B. Fei et al.
laryngeal TB between August 2007 and December 2012. Among them, 45 patients had hoarseness, and 38 suffered from sore throat and foreign body sensation in the throat. Video laryngoscopy showed that the lesions were located at the anterior and middle parts of the vocal cords in 44 patients and in the posterior part in 39 patients. The morphological findings were as follows: pale and edematous mucous membranes near the lesions along with the development of local spotty shallow ulcers (n = 20); hyperplasia of granulation tissue, with its surface covered with pseudomembrane (n = 23); granulation-like neoplasms (n = 22); and nodular uplift (n = 18). In seven patients with a previous history of pulmonary TB, chest X-ray showed old changes; nevertheless, chest X-ray showed no abnormality in the remaining patients. All the patients had good nutritional status and HIV tests were negative. Any one of the following criteria satisfies a diagnosis of laryngeal TB: (a) biopsy of the lesion shows granuloma with caseous necrosis; (b) Mycobacterium tuberculosis is found by pathology; or (c) laryngeal TB is confirmed by fluorescence quantitative PCR for pathologically suspected TB. Control group A total of 52 patients (28 men and 24 women; age, 31–66 years; mean, 48.3 years) with vocal cord polyps during the same period were enrolled as the control group. All presented with hoarseness. Video laryngoscopy showed polypoid changes. The lesions were surgically removed and pathologically confirmed. None of these 52 patients had a history of TB or any TB-related symptoms, and chest X-ray showed no abnormalities. This study was approved by the Ethics Committee of Jin Hu County Hospital and all the patients gave their written informed consent. T-SPOT.TB and tuberculin skin test (TST) were performed by the same senior physician. Fluorescence PCR The DNA from the paraffin-embedded tissues was extracted and amplified using the Real Art M. tuberculosis RG PCR Kit (QIAGEN, Hilden, Germany) following the manufacturer’s protocol. Real-time PCR was performed on a Rotor-Gene 2000 (Corbett Research, Sydney, Australia). The LAN real-time PCR detection system (LG Life Science, Seoul, Korea) was used to measure the fluorescence during PCR. A positive result was indicated when the signal was observed in each channel and the cycle threshold (CT) value was less than 35 cycles.
The selected cut-off value for the differential diagnosis was 1.14 103 copies per ml for quantitative analysis [6]. T-SPOT.TB test A commercial T-SPOT.TB kit (Oxford Immunote Ltd, Oxford, UK) was used. Mononuclear cells were isolated from 5 ml of peripheral blood by density gradient centrifugation. The cells were washed with phosphate-buffered saline (PBS) and adjusted to a density of 2.5 106/ml. In a 96-well plate, the following were added to the respective wells: cell culture medium (blank control); phytohemagglutinin (positive control); ESAT-6 (early secreted antigenic target, 6 kDa); and M. tuberculosis secretory protein CFP-10. An additional 100 ml cell suspension was added to each well. The cells were incubated at 37 C for 16–20 h [7]. The culture medium was discarded and the wells were washed with PBS four times. The cells were incubated with alkaline phosphataselabeled mouse anti-human interferon (IFN)-g monoclonal antibody at 4 C for 1 h. The wells were washed with PBS four times. Nitro-blue tetrazolium/ 5-bromo-4-chloro-3’-indolylphosphate (BCIP/NBT) color development substrate was added for 7 min at room temperature. Deionized water was added to stop the reaction. The criteria for T-SPOT.TB positivity were: (1) when the blank control well had 0–5 blots, the number of blots in the antigen A/B well – number of blots in the blank control well ‡6; or (2) when the blank control well had ‡6 blots, the number of blots in the antigen A/B well ‡ 2 number of blots in the blank control well. Tuberculin skin test (TST) TSTs were performed using the Mantoux method [8]. To perform this test, 0.1 ml of purified protein derivative (PPD) tuberculin containing 5 tuberculin units (TU) was intradermally injected into the ulnar side of the forearm. The results were observed 48–72 h later. The interpretation criteria were as follows: a reaction of ‡5 mm of induration (swelling) with or without blisters or rupture is considered to be TST-positive; absence of induration (swelling) is regarded as negative. Statistical analysis Data were analyzed using SPSS 19.0 software. The T-SPOT.TB and TST results were compared between the laryngeal TB group and control group using a paired chi-squared test, with p < 0.05 considered to be statistically significant.
Diagnosis of laryngeal tuberculosis Table I. Comparison of T-SPOT.TB and TST findings. T-SPOT.TB Test
+
–
Total
TST (+)
36
6
42
TST (–)
39
2
41
Total
75
8
83
Acta Otolaryngol Downloaded from informahealthcare.com by Universitaets- und Landesbibliothek Duesseldorf on 01/03/14 For personal use only.
p Value
0.000
Results T-SPOT.TB In the laryngeal TB group, the T-SPOT.TB was positive in 75 patients and negative in 8 patients. In the control group, the T-SPOT.TB was positive in 4 patients and negative in 48 patients. Hence, the T-SPOT.TB had a sensitivity of 93.3% (75/83) and specificity of 92.3% (48/52) in detecting laryngeal TB.
TST In the laryngeal TB group, the TST was positive in 42 patients and negative in 41 patients. In the control group, the TST was positive in 20 patients and negative in 32 patients. Hence, the TST had a sensitivity of 50.6% (42/83) and specificity of 61.5% (32/52) in detecting laryngeal TB.
Comparison of T-SPOT.TB and TST for the detection of laryngeal TB The comparison of the two tests is summarized in Table I.
Discussion The fourth national epidemiological survey of TB in China showed that the infection rate and prevalence of TB were still high and showed no sign of decreasing [9], which might have resulted from long-term immunization, widespread use of anti-TB drugs, and mutation to the L-type of M. tuberculosis [10]. Laryngeal TB is a chronic infectious disease caused by laryngeal infection with M. tuberculosis, and is the most common form of extrapulmonary TB in the respiratory system. Previously, laryngeal TB was usually secondary to advanced pulmonary TB, with severe systemic and mild laryngeal symptoms. However, the current form of laryngeal TB is characterized by mild systemic and severe local symptoms, such as hoarseness and sore throat [11].
3
Traditionally, laryngeal TB has certain clinical features. In particular, it is often located in the posterior larynx (e.g. arytenoid cartilage). However, it is now more often seen in the anterior part of the larynx including the vocal cords [12], ventricular band, and epiglottis. This makes the diagnosis somewhat difficult. Pathological examination is the gold standard for diagnosis of laryngeal TB. The typical pathology of laryngeal TB is epithelioid granuloma and cheesy necrosis, with lymphocytic infiltration and scattered Langerhans giant cells. Possible reasons for this low rate of pathologically confirmed laryngeal TB include: (1) inadequate sampling of the laryngeal tissue due to the risk of compromised vocal quality; and (2) samples were compressed during the sampling procedure, which led to atypical pathological results. TST is the traditionally used immunoassay for cellular immunity against M. tuberculosis, but its specificity is low due to cross-reaction with BCG and other Mycobacterium strains. Our study also showed that TST is low in diagnostic performance for laryngeal TB. The specificity of TST could be increased by setting the mean diameter of induration at ‡10 mm as the threshold for positivity [13], which might lead to increased false negativity. Activated T lymphocytes can release IFN-g upon stimulation by specific antigens of M. tuberculosis [14], which is also the mechanism of the T-SPOT.TB test. This novel test can determine the infection state by detecting the amount of IFN-g released by T cells [14]. In addition, the T-SPOT.TB test is able to differentiate TB from granulomatous lesions such as sarcoidosis and Wegener’s granulomatosis. T-SPOT.TB provides definite results in a manner of ‘all or none,’ and requires less than 24 h to perform. According to Lalvani [15], the T-SPOT.TB test had a sensitivity of 83.0–97.0% (pooled sensitivity, 90%) for active TB in adults with normal immune function. In their meta-analysis, Pai et al. [16] found that the specificity of the T-SPOT.TB in diagnosing TB was 93.0%. In the present study, the T-SPOT.TB test was positive in 75 patients with confirmed laryngeal TB, yielding a sensitivity of 90.3%; in the control group, the sensitivity reached 92.3%. These findings are consistent with the literature. In summary, the sensitivity of the T-SPOT.TB is remarkably higher than that of the conventional tests in terms of detecting M. tuberculosis; this test will therefore play a role in the early diagnosis of laryngeal TB. However, our subjects did not include young children, and the role of the T-SPOT.TB in the diagnosis of TB in children requires further investigation.
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4
B. Fei et al.
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
[8]
References
[9]
[1] WHO. Global tuberculosis control: WHO report 2011. Geneva: WHO. 2011. [2] Pai M, Joshi R, Dogra S, Mendiratta DK, Narang P, Dheda K, et al. Persistently elevated T cell interferon-gamma responses after treatment for latent tuberculosis infection among health care workers in India: a preliminary report. J Occup Med Toxicol 2006;23:7. [3] Dye C. Global epidemiology of tuberculosis. Lancet 2006; 367:938–40. [4] Singh B, Balwally AN, Nash M, Har-El G, Lucente FE. Laryngeal tuberculosis in HIV-infected patients: a difficult diagnosis. Laryngoscope 1996;106:1238–40. [5] Rizzo PB, Da Mosto MC, Clari M, Scotton PG, Vaglia A, Marchiori C. Laryngeal tuberculosis: an often forgotten diagnosis. Int J Infect 2003;7:129–31. [6] Zhou Y, Li HP, Li QH, Zheng H, Zhang RX, Chen G, et al. Differentiation of sarcoidosis from tuberculosis using realtime PCR assay for the detection and quantification of Mycobacterium tuberculosis. Sarcoidosis Vasc Diffuse Lung Dis 2008;25:93–9. [7] Nkurunungi G, Lutangira JE, Lule SA, Akurut H, Kizindo R, Fitchett JR, et al. Determining Mycobacterium
[10]
[11] [12]
[13]
[14]
[15]
[16]
tuberculosis infection among BCG-immunised Ugandan children by T-SPOT.TB and tuberculin skin testing. PLoS ONE 2012;7:e47340. American Thoracic Society. Targeted tuberculin testing and treatment of latent tuberculosis infection. Am J Respir Crit Care Med 2000;161:S221–47. National Technic Steering Group of the Epidemiological Sampling Survey for Tuberculosis. Report on fourth national epidemiological sampling survey of tuberculosis. Zhonghua Jie He He Hu Xi Za Zhi 2002;25:3–7. Zhang DR. Clinical and epidemiological significances of L forms of Mycobacterium tuberculosis. Zhonghua Jie He He Hu Xi Za Zhi 1993;16:181–3. Chen HK, Thornley P. Laryngeal tuberculosis. A case of a nonhealing laryngeal lesion. Australas Med J 2012;5:175–7. Shin JE, Nam SY, Yoo SJ, Kim SY. Changing trends in clinical manifestations of laryngeal tuberculosis. Laryngoscope 2000;110:1950–3. Fine PE, Sterne JA, Ponnighaus JM, Rees RJ. Delayed-type hypersensitivity, mycobacterial vaccines and protective immunity. Lancet 1994;344:1245–9. Kakkar F, Allen U, Ling D, Pai M, Kitai I. Tuberculosis in children: new diagnostic blood tests. Paediatr Child Health 2010;15:529–33. Lalvani A. Diagnosing tuberculosis infection in the 21st century: new tools to tackle an old enemy. Chest 2007; 131:1898–906. Pai M, Zwerling A, Menzies D. Systematic review: T-cell-based assays for the diagnosis of latent tuberculosis infection: an update. Ann Intern Med 2008;149:177–84.
ORIGINAL ARTICLE
Acta Otolaryngol Downloaded from informahealthcare.com by Universitaets- und Landesbibliothek Duesseldorf on 01/03/14 For personal use only.
Interferon-g release assay in the diagnosis of laryngeal tuberculosis
BING FEI*1,2, ZHENG WU*3, KEHUA MIN2, JINGBO ZHANG2, CHUANLIAN DING2 & HAO WU1 1
Department of Otolaryngology-Head and Neck Surgery, Affiliated Hospital of Nantong University, Nantong, Jiangsu, PR China, 2Department of Otolaryngology, Jin Hu People’s Hospital, Huai An, Jiangsu, PR China and 3Department of Otolaryngology, Chang Shu Second People’s Hospital, Su Zhou, Jiangsu, PR China
Abstract Conclusion: The T-SPOT test for Mycobacterium tuberculosis infection (T-SPOT.TB) can be used for early diagnosis of laryngeal tuberculosis (TB). Objective: The incidence of TB is increasing on a global scale. Laryngeal TB is the most common extrapulmonary form of TB and its early diagnosis is still difficult. This study investigated the performance of the interferon-g release assay in the diagnosis of laryngeal TB. Methods: A total of 83 patients with laryngeal neoplasms were confirmed to have laryngeal TB by pathology, acid-fast staining, and/or fluorescence quantitative PCR. In addition, 52 patients with vocal cord polyps were enrolled as the control group. Two groups underwent both T-SPOT.TB and tuberculin skin test (TST). Results: T-SPOT.TB was positive in 75 cases in the laryngeal TB group and 4 cases in the control group, showing a sensitivity of 90.3% (75/83) and a specificity of 92.3% (48/52). The TST was positive in 42 cases and 20 cases, respectively, in these two groups. Obviously, TST and T-SPOT.TB were significantly different in terms of sensitivity when applied for detection of laryngeal TB (p < 0.05).
Keywords: T-SPOT.TB, tuberculin skin test, diagnosis, specificity
Introduction Worldwide, tuberculosis (TB) remains one of the most important infectious causes of mortality. In 2010, there were an estimated 8.8 million incident cases and approximately 1.4 million people died from this disease [1]. A vast pool of individuals with latent TB infection (LTBI) persists in developing countries, posing a major barrier to global TB control [2]. China is among the 22 countries with the heaviest TB burdens and has the second largest TB population in the world. There are about 0.55 billion people infected, which is a much higher infection rate than the global rate of 1/3 of the population all over the world have infected TB [3]. The prevalence of TB has increased for a variety of reasons including the overuse of antibiotics, mutation of Mycobacterium tuberculosis, antibiotic resistance, diabetes mellitus,
and AIDS and other immunodeficiency disorders [4]. Laryngeal TB is the most common type of extrapulmonary TB and varies greatly in disease onset and signs and symptoms, leading to a high rate of misdiagnosis [5]. The T-SPOT test for Mycobacterium tuberculosis infection (T-SPOT.TB) has been widely used in the diagnosis of pulmonary TB, but its application in the diagnosis of laryngeal TB has not been reported. In this study, we investigated the performance of T-SPOT.TB in the diagnosis of laryngeal TB. Materials and methods Patients A total of 83 patients (46 men and 37 women; age, 30–65 years; mean, 47.1 years) were found to have
Correspondence: Professor Hao Wu, Department of Otolaryngology-Head and Neck Surgery, Affiliated Hospital of Nantong University, Nantong, Jiangsu Province, 226001, People’s Republic of China. Tel: +86 13706294560. E-mail: [email protected] *These authors contributed equally to this work.
(Received 22 July 2013; accepted 21 September 2013) ISSN 0001-6489 print/ISSN 1651-2251 online 2013 Informa Healthcare DOI: 10.3109/00016489.2013.850174
Acta Otolaryngol Downloaded from informahealthcare.com by Universitaets- und Landesbibliothek Duesseldorf on 01/03/14 For personal use only.
2
B. Fei et al.
laryngeal TB between August 2007 and December 2012. Among them, 45 patients had hoarseness, and 38 suffered from sore throat and foreign body sensation in the throat. Video laryngoscopy showed that the lesions were located at the anterior and middle parts of the vocal cords in 44 patients and in the posterior part in 39 patients. The morphological findings were as follows: pale and edematous mucous membranes near the lesions along with the development of local spotty shallow ulcers (n = 20); hyperplasia of granulation tissue, with its surface covered with pseudomembrane (n = 23); granulation-like neoplasms (n = 22); and nodular uplift (n = 18). In seven patients with a previous history of pulmonary TB, chest X-ray showed old changes; nevertheless, chest X-ray showed no abnormality in the remaining patients. All the patients had good nutritional status and HIV tests were negative. Any one of the following criteria satisfies a diagnosis of laryngeal TB: (a) biopsy of the lesion shows granuloma with caseous necrosis; (b) Mycobacterium tuberculosis is found by pathology; or (c) laryngeal TB is confirmed by fluorescence quantitative PCR for pathologically suspected TB. Control group A total of 52 patients (28 men and 24 women; age, 31–66 years; mean, 48.3 years) with vocal cord polyps during the same period were enrolled as the control group. All presented with hoarseness. Video laryngoscopy showed polypoid changes. The lesions were surgically removed and pathologically confirmed. None of these 52 patients had a history of TB or any TB-related symptoms, and chest X-ray showed no abnormalities. This study was approved by the Ethics Committee of Jin Hu County Hospital and all the patients gave their written informed consent. T-SPOT.TB and tuberculin skin test (TST) were performed by the same senior physician. Fluorescence PCR The DNA from the paraffin-embedded tissues was extracted and amplified using the Real Art M. tuberculosis RG PCR Kit (QIAGEN, Hilden, Germany) following the manufacturer’s protocol. Real-time PCR was performed on a Rotor-Gene 2000 (Corbett Research, Sydney, Australia). The LAN real-time PCR detection system (LG Life Science, Seoul, Korea) was used to measure the fluorescence during PCR. A positive result was indicated when the signal was observed in each channel and the cycle threshold (CT) value was less than 35 cycles.
The selected cut-off value for the differential diagnosis was 1.14 103 copies per ml for quantitative analysis [6]. T-SPOT.TB test A commercial T-SPOT.TB kit (Oxford Immunote Ltd, Oxford, UK) was used. Mononuclear cells were isolated from 5 ml of peripheral blood by density gradient centrifugation. The cells were washed with phosphate-buffered saline (PBS) and adjusted to a density of 2.5 106/ml. In a 96-well plate, the following were added to the respective wells: cell culture medium (blank control); phytohemagglutinin (positive control); ESAT-6 (early secreted antigenic target, 6 kDa); and M. tuberculosis secretory protein CFP-10. An additional 100 ml cell suspension was added to each well. The cells were incubated at 37 C for 16–20 h [7]. The culture medium was discarded and the wells were washed with PBS four times. The cells were incubated with alkaline phosphataselabeled mouse anti-human interferon (IFN)-g monoclonal antibody at 4 C for 1 h. The wells were washed with PBS four times. Nitro-blue tetrazolium/ 5-bromo-4-chloro-3’-indolylphosphate (BCIP/NBT) color development substrate was added for 7 min at room temperature. Deionized water was added to stop the reaction. The criteria for T-SPOT.TB positivity were: (1) when the blank control well had 0–5 blots, the number of blots in the antigen A/B well – number of blots in the blank control well ‡6; or (2) when the blank control well had ‡6 blots, the number of blots in the antigen A/B well ‡ 2 number of blots in the blank control well. Tuberculin skin test (TST) TSTs were performed using the Mantoux method [8]. To perform this test, 0.1 ml of purified protein derivative (PPD) tuberculin containing 5 tuberculin units (TU) was intradermally injected into the ulnar side of the forearm. The results were observed 48–72 h later. The interpretation criteria were as follows: a reaction of ‡5 mm of induration (swelling) with or without blisters or rupture is considered to be TST-positive; absence of induration (swelling) is regarded as negative. Statistical analysis Data were analyzed using SPSS 19.0 software. The T-SPOT.TB and TST results were compared between the laryngeal TB group and control group using a paired chi-squared test, with p < 0.05 considered to be statistically significant.
Diagnosis of laryngeal tuberculosis Table I. Comparison of T-SPOT.TB and TST findings. T-SPOT.TB Test
+
–
Total
TST (+)
36
6
42
TST (–)
39
2
41
Total
75
8
83
Acta Otolaryngol Downloaded from informahealthcare.com by Universitaets- und Landesbibliothek Duesseldorf on 01/03/14 For personal use only.
p Value
0.000
Results T-SPOT.TB In the laryngeal TB group, the T-SPOT.TB was positive in 75 patients and negative in 8 patients. In the control group, the T-SPOT.TB was positive in 4 patients and negative in 48 patients. Hence, the T-SPOT.TB had a sensitivity of 93.3% (75/83) and specificity of 92.3% (48/52) in detecting laryngeal TB.
TST In the laryngeal TB group, the TST was positive in 42 patients and negative in 41 patients. In the control group, the TST was positive in 20 patients and negative in 32 patients. Hence, the TST had a sensitivity of 50.6% (42/83) and specificity of 61.5% (32/52) in detecting laryngeal TB.
Comparison of T-SPOT.TB and TST for the detection of laryngeal TB The comparison of the two tests is summarized in Table I.
Discussion The fourth national epidemiological survey of TB in China showed that the infection rate and prevalence of TB were still high and showed no sign of decreasing [9], which might have resulted from long-term immunization, widespread use of anti-TB drugs, and mutation to the L-type of M. tuberculosis [10]. Laryngeal TB is a chronic infectious disease caused by laryngeal infection with M. tuberculosis, and is the most common form of extrapulmonary TB in the respiratory system. Previously, laryngeal TB was usually secondary to advanced pulmonary TB, with severe systemic and mild laryngeal symptoms. However, the current form of laryngeal TB is characterized by mild systemic and severe local symptoms, such as hoarseness and sore throat [11].
3
Traditionally, laryngeal TB has certain clinical features. In particular, it is often located in the posterior larynx (e.g. arytenoid cartilage). However, it is now more often seen in the anterior part of the larynx including the vocal cords [12], ventricular band, and epiglottis. This makes the diagnosis somewhat difficult. Pathological examination is the gold standard for diagnosis of laryngeal TB. The typical pathology of laryngeal TB is epithelioid granuloma and cheesy necrosis, with lymphocytic infiltration and scattered Langerhans giant cells. Possible reasons for this low rate of pathologically confirmed laryngeal TB include: (1) inadequate sampling of the laryngeal tissue due to the risk of compromised vocal quality; and (2) samples were compressed during the sampling procedure, which led to atypical pathological results. TST is the traditionally used immunoassay for cellular immunity against M. tuberculosis, but its specificity is low due to cross-reaction with BCG and other Mycobacterium strains. Our study also showed that TST is low in diagnostic performance for laryngeal TB. The specificity of TST could be increased by setting the mean diameter of induration at ‡10 mm as the threshold for positivity [13], which might lead to increased false negativity. Activated T lymphocytes can release IFN-g upon stimulation by specific antigens of M. tuberculosis [14], which is also the mechanism of the T-SPOT.TB test. This novel test can determine the infection state by detecting the amount of IFN-g released by T cells [14]. In addition, the T-SPOT.TB test is able to differentiate TB from granulomatous lesions such as sarcoidosis and Wegener’s granulomatosis. T-SPOT.TB provides definite results in a manner of ‘all or none,’ and requires less than 24 h to perform. According to Lalvani [15], the T-SPOT.TB test had a sensitivity of 83.0–97.0% (pooled sensitivity, 90%) for active TB in adults with normal immune function. In their meta-analysis, Pai et al. [16] found that the specificity of the T-SPOT.TB in diagnosing TB was 93.0%. In the present study, the T-SPOT.TB test was positive in 75 patients with confirmed laryngeal TB, yielding a sensitivity of 90.3%; in the control group, the sensitivity reached 92.3%. These findings are consistent with the literature. In summary, the sensitivity of the T-SPOT.TB is remarkably higher than that of the conventional tests in terms of detecting M. tuberculosis; this test will therefore play a role in the early diagnosis of laryngeal TB. However, our subjects did not include young children, and the role of the T-SPOT.TB in the diagnosis of TB in children requires further investigation.
Acta Otolaryngol Downloaded from informahealthcare.com by Universitaets- und Landesbibliothek Duesseldorf on 01/03/14 For personal use only.
4
B. Fei et al.
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
[8]
References
[9]
[1] WHO. Global tuberculosis control: WHO report 2011. Geneva: WHO. 2011. [2] Pai M, Joshi R, Dogra S, Mendiratta DK, Narang P, Dheda K, et al. Persistently elevated T cell interferon-gamma responses after treatment for latent tuberculosis infection among health care workers in India: a preliminary report. J Occup Med Toxicol 2006;23:7. [3] Dye C. Global epidemiology of tuberculosis. Lancet 2006; 367:938–40. [4] Singh B, Balwally AN, Nash M, Har-El G, Lucente FE. Laryngeal tuberculosis in HIV-infected patients: a difficult diagnosis. Laryngoscope 1996;106:1238–40. [5] Rizzo PB, Da Mosto MC, Clari M, Scotton PG, Vaglia A, Marchiori C. Laryngeal tuberculosis: an often forgotten diagnosis. Int J Infect 2003;7:129–31. [6] Zhou Y, Li HP, Li QH, Zheng H, Zhang RX, Chen G, et al. Differentiation of sarcoidosis from tuberculosis using realtime PCR assay for the detection and quantification of Mycobacterium tuberculosis. Sarcoidosis Vasc Diffuse Lung Dis 2008;25:93–9. [7] Nkurunungi G, Lutangira JE, Lule SA, Akurut H, Kizindo R, Fitchett JR, et al. Determining Mycobacterium
[10]
[11] [12]
[13]
[14]
[15]
[16]
tuberculosis infection among BCG-immunised Ugandan children by T-SPOT.TB and tuberculin skin testing. PLoS ONE 2012;7:e47340. American Thoracic Society. Targeted tuberculin testing and treatment of latent tuberculosis infection. Am J Respir Crit Care Med 2000;161:S221–47. National Technic Steering Group of the Epidemiological Sampling Survey for Tuberculosis. Report on fourth national epidemiological sampling survey of tuberculosis. Zhonghua Jie He He Hu Xi Za Zhi 2002;25:3–7. Zhang DR. Clinical and epidemiological significances of L forms of Mycobacterium tuberculosis. Zhonghua Jie He He Hu Xi Za Zhi 1993;16:181–3. Chen HK, Thornley P. Laryngeal tuberculosis. A case of a nonhealing laryngeal lesion. Australas Med J 2012;5:175–7. Shin JE, Nam SY, Yoo SJ, Kim SY. Changing trends in clinical manifestations of laryngeal tuberculosis. Laryngoscope 2000;110:1950–3. Fine PE, Sterne JA, Ponnighaus JM, Rees RJ. Delayed-type hypersensitivity, mycobacterial vaccines and protective immunity. Lancet 1994;344:1245–9. Kakkar F, Allen U, Ling D, Pai M, Kitai I. Tuberculosis in children: new diagnostic blood tests. Paediatr Child Health 2010;15:529–33. Lalvani A. Diagnosing tuberculosis infection in the 21st century: new tools to tackle an old enemy. Chest 2007; 131:1898–906. Pai M, Zwerling A, Menzies D. Systematic review: T-cell-based assays for the diagnosis of latent tuberculosis infection: an update. Ann Intern Med 2008;149:177–84.
