Serological diagnosis of pulmonary tuberculosis and nontuberculous pulmonary mycobacteriosis]

OBJECTIVE: The present study was undertaken to evaluate the utility of the serodiagnosis of pulmonary tuberculosis and nontuberculous pulmonary mycobacteriosis by ELISA using a Pathozyme-Myco kit (Myco kit) and a Pathozyme-TB complex kit (TB kit) (OMEGA Diagnostics Ltd.). STUDY POPULATION: The subjects comprised 256 healthy volunteers (HV, healthy hospital employees), 66 patients with sputum-positive active pulmonary tuberculosis (apTB), 14 patients with healed pulmonary tuberculosis (hpTB), 24 patients with nontuberculous pulmonary mycobacteriosis (NTM) and 32 patients with pulmonary diseases other than mycobacteriosis. RESULTS: 1) The serum IgG antibody titers determined with the Myco kit were significantly higher in the apTB group (p < 0.01), the hpTB group (p < 0.01), and the NTM group (p < 0.01) than those in the HV and the other pulmonary disease group. At a cut-off value of the mean + 2SD of the values obtained in the HV, the positive rate was 47.0% in patients with apTB, 50.0% in those with NTM, 21.4% in those with hpTB, 3.1% in those with other pulmonary diseases, and 1.6% in the HV. Analysis of ROC curves showed that the HV and the pulmonary mycobacteriosis group (apTB and NTM) were best distinguished by a cut-off value of -0.280 OD (log), with the sensitivity and the specificity being 83.3% and 78.5%, respectively. It was impossible to distinguish apTB from NTM. 2) The serum IgG antibody titers determined with the TB kit were significantly higher in the apTB group than those in the HV (p < 0.01), the NTM group (p < 0.05) and the other pulmonary disease group (p < 0.01). No significant difference was observed between the HV and the patients with NTM or those with other pulmonary diseases. Although the positive rate of the test was low in the apTB group (42.4%), there was a significant difference between apTB and NTM (12.5%) (p < 0.05), suggesting that apTB could be distinguished from NTM. 3) Since the serum antibody titers determined by the Myco kit showed no significant difference between apTB and NTM, and there was also no difference in the positivity between the two diseases, we performed serologic examination using the Myco kit to detect both diseases as pulmonary mycobacteriosis. After diagnosing pulmonary mycobacteriosis by the Myco kit, we then used the TB kit to separate apTB from NTM. In this case, the sensitivity and specificity of the test were 55.6% and 85.7%, respectively. Better methods should be developed to distinguish apTB from nontuberculous mycobacteriosis.     

Humoral immune response against 38‐ and 16‐kDa mycobacterial antigens in childhood tuberculosis

Several enzyme‐linked immunosorbent assays (ELISAs) based on mycobacterial antigens have been tried for the rapid diagnosis of tuberculosis (TB). In this study, the value of the 16 and 38‐kDa mycobacterial antigens in the diagnosis of TB was investigated in pediatric patients in Izmir, Turkey in whom they were found using clinical and/or bacteriological methods. A commercial ELISA kit was used for measuring IgG against 38 and 16‐kDa recombinant antigens. The humoral immune response was analyzed in a group of 32 TB patients (24 pulmonary, 3 lymphadenitis and 2 pleuritis, 2 meningitis and a disseminated TB) and in control groups consisting of 20 healthy children and 20 pulmonary diseases other than TB cases. The sensitivity, specificity, positive predictive value, and the negative predictive value of the test were found to be 25%, 90%, 66.7%, and 60%, respectively, in the TB cases. The ELISA test shows very good specificity, but low level of sensitivity and negative predict value. It was thought that it might be used in combination with other methods to increase diagnostic accuracy, especially for culture‐negative TB pediatric cases, which are difficult to diagnose. Pediatr Pulmonol. 2009; 44:839–844. © 2009 Wiley‐Liss, Inc.     

Humoral response to Mycobacterium tuberculosis-specific antigens in African tuberculosis patients with high prevalence of Human immunodeficiency virus infection

Setting: The applicability of serodiagnosis of tuberculosis using Mycobacterium tuberculosis-complex-specific antigens in a Tanzanian population with high prevalence of HIV.Objective: This study was performed to evaluate the usefulness, sensitivity and specificity of serology using M. tuberculosis-specific antigens in the diagnosis of tuberculosis in patients with and without HIV co-infection.Design: Patients with proven pulmonary and extrapulmonary tuberculosis at a major referral centre in Tanzania were enrolled in the study. The control group consisted of patients without a history of previous tuberculosis admitted to the trauma ward and of healthy volunteers. Sera were analysed by an enzyme linked immunoassay (ELISA) using two M. tuberculosis specific proteins as antigen: the 38 kDa protein [3t]and a 17 kDa protein. In addition was recorded presence or absence of BCG scar and tuberculin sensitivity and the sera were tested for HIV and analysed for β-2-microglobulin content.Result: Sensitivity and specificity were markedly reduced in tuberculosis patients with HIV co-infection compared to patients without this disease (73% and 70% versus 52% and 50% respectively).Conclusion: Serology for diagnosis of tuberculosis is not feasible in an HIV endemic region.     

T-SPOT.TB Test(R) results in adults with Mycobacterium avium complex pulmonary disease

The tuberculin skin test is limited by its inability to distinguish between infection with Mycobacterium tuberculosis and non-tuberculous mycobacteria (NTM). Newer interferon-gamma release assays using ESAT-6 and CFP-10 antigens should have a higher specificity for tuberculosis but have not been widely tested in adults with pulmonary disease due to NTM. In this study, we tested the T-SPOT.TB Test in patients with pulmonary disease due to Mycobacterium avium complex (MAC), the most common disease-causing NTM. Fourteen patients with prior culture-confirmed pulmonary disease due to MAC, 10 patients with prior culture-confirmed tuberculosis and 4 healthy controls were interviewed and tested with the T-SPOT.TB Test. 13 patients with MAC disease and 4 healthy subjects (negative controls) had non-reactive T-SPOT.TB results and 10 patients with prior tuberculosis (positive controls) had reactive results. One patient with MAC disease had a minimally reactive result on initial testing and a non-reactive result on re-testing. The T-SPOT.TB Test had a specificity of 94% for distinguishing between patients with prior MAC disease and prior tuberculosis disease, and will be useful in low tuberculosis prevalence settings where most mycobacterial infections are due to MAC. Reactions to the T-SPOT.TB Test may persist months to years after treatment of tuberculosis.     

两种结核分枝杆菌相关γ-干扰素定量检测试剂盒检测结核分枝杆菌感染结果比较研究

目的 评价新的国产结核分枝杆菌相关γ-干扰素定量检测试剂盒（TB-IGRA）--体外释放酶联免疫法诊断结核病的敏感性和特异性。 方法 采用TB-IGRA试剂盒对319例肺结核、23例肺外结核、39例排除结核的肺部疾病和104例健康人群的血清标本进行检测,同时与澳大利亚Cellestis公司的QuantiFERON-TB GOLD in tube（QFT-GIT）试剂进行平行比较分析。 结果 采用TB-IGRA试剂,检测肺结核病人的敏感性为90.9%,肺外结核的敏感性为78.3%,特异性为76.9%;采用QFT-GIT试剂,检测肺结核病人的敏感性为88.4%,肺外结核的敏感性为78.3%,特异性为80.4%,2种试剂进行平行比较,敏感性和特异性方面差异无统计学意义。 结论 TB-IGRA试剂盒对诊断结核病有较高的敏感性和特异性,可用于结核病尤其是涂阴肺结核和肺外结核的辅助诊断。     

Evaluation of a serologic test for the diagnosis of tuberculosis.

The ICT TB test, a new, simple, serologic diagnostic test for tuberculosis (TB), was performed on serum samples from individuals seen at an urban teaching hospital and a local health department clinic. The study population included cases of TB, disease with mycobacteria other than tuberculosis (MOTT), non-mycobacterial pulmonary disease, and healthy controls. In contrast to prior studies, we found the ICT TB test had little value in detection of new cases of TB (overall sensitivity was 20%). It had very low sensitivity (4%) in the first month of disease. The sensitivity improved in patients tested at least 3 months after clinical presentation, but still remained fairly low. The test was also positive in 30% cases of disease caused by MOTT demonstrating cross-reactivity. It was negative in all human immunodeficiency virus (HIV) positive cases of TB or MOTT. The overall specificity was 89%. At least part of the discrepancy between our results and those of previous investigators may be attributable to differences in the respective study populations, including incidence of HIV disease and duration of tuberculosis illness prior to testing.     

Mycobacterium tuberculosis lipid antigens: use of multi-antigen based enzyme immunoassay for free and complex dissociated antibodies.

OBJECTIVE: To test the sensitivity and specificity of four lipid antigens of Mycobacterium tuberculosis: BDA-TDA, DAT, SL-I, and PIMs, adsorbed in the same microplate well, to detect reactive IgG by enzyme-immunoassay (EIA) from plain serum (MA-EIA) and dissociated immune complexes (ICMA-EIA). DESIGN: IgG antibodies against four antigens, placed in the same microplate well, were evaluated in serum from 155 tuberculous (TB) cases non-infected with the human immunodeficiency virus (HIV): 78 patients with positive bacilloscopy and culture, 33 patients with positive culture and 44 patients diagnosed by clinical and radiological criteria; and from 211 HIV negative control subjects: 32 patients with other pulmonary diseases, 100 healthy people and 79 close contacts. RESULTS: MA-EIA had an overall sensitivity and specificity of 61% (94/155) and 95% (200/211), respectively. We further examined whether the dissociation of immune complexes increases the number of positive reactions in those initially found to be seronegative (SN). The subset of 112 (76 controls and 36 TB) MA-EIA SN samples tested using ICMA-EIA yielded an overall sensitivity and specificity of 83% and 100%. The ICMA-EIA results improved the overall sensitivity from 61 to 80% without changing specificity. CONCLUSION: These preliminary results suggest that MA-EIA followed by ICMA-EIA, for SN samples, might serve as a fast, cheap, and easy method for the diagnosis of TB in less than 48 hours.     

不同结核分支杆菌抗原对结核病的诊断价值

目的　研究不同结核分支杆菌单体蛋白抗原在结核病体液免疫诊断中的价值。方法以快速免疫色谱法（ＩＣＴＴＢ卡） 检测结核分支杆菌５ 种单体蛋白的抗原性，观察其在结核病诊断中的敏感性和特异性，并与ＰＰＤ 皮试及脂阿拉伯糖甘露糖（ＬＡＭ） 相比较。结果　ＩＣＴＴＢ 卡、ＬＡＭ 及ＰＰＤ皮试诊断结核病的敏感性分别为５５．９％ 、５２．６％ 、７５．０％ ，后者与前二者间差异均有显著意义（ Ｐ＜０ ．０５）；ＩＣＴＴＢ卡、ＬＡＭ、ＰＰＤ皮试诊断肺结核的特异性为８７ ．６％ 、６２．９％ 、６８．９％ ，前者与后二者间差异均有非常显著意义（ Ｐ＜ ０．０１）；ＩＣＴＴＢ卡诊断肺结核病的临床阳性预计值为８８ ．５％ ，临床阴性预计值为５３ ．８ ％ ；非结核病例中的ＩＣＴＴＢ阳性主要由抗原４、５ 阳性所致，如果去除抗原４ 、５，那么ＩＣＴＴＢ诊断结核病的特异性将提高到９８．９％ 。结论　血清结核分支杆菌单体蛋白抗原性的测定是肺结核病一项有用的辅助诊断手段。     

Treatment results of DOTS in 1797 Sudanese tuberculosis patients with or without HIV co-infection.

SETTING: Consecutive new tuberculosis (TB) patients, from eight states in Sudan, who had never been previously treated for as much as 1 month between 1998 and 2000. OBJECTIVE: To determine the impact of human immunodeficiency virus (HIV) co-infection on tuberculosis treatment outcome. DESIGN: All patients presenting with symptoms suggestive of tuberculosis underwent sputum microscopy for acid-fast bacilli (AFB). Treatment is free of charge, and directly observed for all smear-positive patients. Treatment outcomes were those defined by the World Health Organization. All patients were tested anonymously for human immunodeficiency virus (HIV) using the Bionor test. RESULTS: Of 10 494 patients suspected of TB and referred for sputum microscopy, 1797 were TB cases; 983 had smear-positive pulmonary tuberculosis, 521 smear-negative pulmonary tuberculosis, and 293 extra-pulmonary tuberculosis. Smear-positive cases showed a cure rate of 77.2% and a failure rate of 1%. Smear-negative and extra-pulmonary patients had a completion rate of 79.4%. Cure rates for the smear-positive cases were 68.3% for HIV-positive and 77.6% for HIV-negative patients (P = 0.164). Case fatality was significantly higher among HIV-positive (12%) than among HIV-negative cases (1.8%) (OR 7.7, 95% CI 3.51-16.8). CONCLUSION: To date, a relatively low proportion of tuberculosis patients in Sudan also have HIV infection. These patients are substantially more likely to die while on treatment for their tuberculosis, a fact that underlines their need for more comprehensive care if their lives are to be prolonged. In addition, every effort is required to diminish the transmission of HIV infection to prevent the tragedy this infection represents to the community.     

Humoral immune response against 38-kDa and 16-kDa mycobacterial antigens in tuberculosis.

Several ELISA tests based on mycobacterial antigens have been used for the rapid diagnosis of tuberculosis (TB), although demonstration of Mycobacterium tuberculosis in a smear or culture is the most reliable method. In the present study, the diagnostic value of 16-kDa and 38-kDa mycobacterial antigens was investigated in patients who were diagnosed with tuberculosis by clinical and/or bacteriological findings in Turkey. The PATHOZYME-TB Complex Plus commercial ELISA kit was used for measuring immunoglobulin G against 38-kDa and 16-kDa recombinant antigens. Humoral immune response was analysed in a group of 179 TB patients (143 smear-positive, 19 smear-negative, eight lymphadenitis and nine pleuritis), 15 inactive TB cases and in control groups consisting of 40 healthy volunteers and 20 subjects with pulmonary diseases other than TB. The sensitivity, specifity, positive predictive value and negative predictive value of the test were determined at 52.5%, 93.3%, 95.9% and 39.7%, respectively in TB cases. Antibodies were detected at above cut-off level in three (20%) out of 15 subjects with inactive TB. In conclusion, the ELISA test has a very good specifity and an acceptable sensitivity and positive predictive value. It is thought that it could be used in combination with other methods to increase diagnostic accuracy, especially for culture-negative tuberculosis cases, which are difficult to diagnose.     

Prospective study of a new serological test (ASSURE TB Rapid Test) for the diagnosis of pulmonary tuberculosis.

OBJECTIVE: To prospectively compare a rapid tuberculosis serological test, ASSURE TB Rapid Test, with traditional smear and culture methods for the diagnosis of pulmonary tuberculosis (PTB). DESIGN: All consecutive in-patients aged > or = 18 years suspected of having active PTB and admitted between June 2001 and March 2003 were tested with three sputum samples for smear and culture of Mycobacterium tuberculosis and serology (done within 3 days). RESULTS: Of 238 patients initially enrolled (male: female 2.5:1, mean age 56.6 years), the final analysis included 216 patients. For the final diagnosis of PTB, the sensitivity and specificity of the serological test were respectively 60.2% (95%CI 50.5-69.1) and 82.3% (95%CI 74.2-88.2) compared to 53.4% (95%CI 43.8-62.7) and 98.2% (95%CI 93.8-99.5) for the smear test. A combination of smear and serology provided an increased sensitivity of 74.8% (95%CI 65.6-82.2), but a lower specificity of 80.5% (95%CI 72.3-86.8). CONCLUSION: The new serological test showed a moderate increase in sensitivity but a decrease in specificity compared to smear examination. The combination (smear + serology) test further increased the sensitivity while maintaining a moderate specificity.     

Rapid liposomal agglutination card test for the detection of antigens in patients with active tuberculosis.

SETTING: A total of 1360 subjects with clinically confirmed pulmonary and extra-pulmonary tuberculosis (TB) and other non-tuberculous conditions. OBJECTIVES: To develop a rapid, sensitive and specific diagnostic test for the detection of the glycolipid antigen of Mycobacterium tuberculosis in a variety of clinical samples. STUDY DESIGN: Affinity-purified rabbit anti-glycolipid antibodies (IgG) were coupled to liposome particles (0.2-0.4 microm) in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinamide to prepare the working reagent of the TB/M card test. RESULTS: Antibody-conjugated liposomes, when determined with the glycolipid antigens present in the specimens, formed a dark blue agglutination within 4 min. No clumping was observed in samples from normal healthy subjects or patients with other diseases. The test was shown to be effective in detecting glycolipid antigens of M. tuberculosis in clinical samples from patients with active TB with as low as 1 ng/ml analytical sensitivity, 97.4% clinical sensitivity and 96.9% specificity. CONCLUSION: The TB/M card test was found to be comparatively economical (4 Indian Rupees or US$ 0.09/test), rapid (4 min) and seems fairly useful for mass testing of a variety of biological specimens (cerebrospinal, pleural and synovial fluids, serum, tissue biopsy extract) from patients with tuberculous meningitis, pulmonary TB and other extra-pulmonary TB in endemic countries.     

Influence of HLA-DR antigens on lymphocyte response to Mycobacterium tuberculosis culture filtrate antigens and mitogens in pulmonary tuberculosis.

SETTING: Influence of HLA-DR antigens and lymphocyte responses in pulmonary TB patients. OBJECTIVE: To elucidate the role of HLA-DR genes/gene products on lymphocyte responses to Mycobacterium tuberculosis antigens and mitogens, the present study was carried out in pulmonary tuberculosis during active and cured stage of the disease. DESIGN: Serological determination of HLA-DR antigens was carried out in 50 active TB patients, 44 cured TB patients and 58 normal healthy control subjects. The influence of HLA-DR antigens on peripheral blood lymphocyte responses to M. tuberculosis culture filtrate antigens and mitogens such as phytohaemagglutinin (PHA) and concanavalin-A (Con-A) was studied in the patients as well as normal healthy control subjects. RESULTS: Of all the DR antigens studied, patients (active TB and cured TB) with DR2 antigen showed an increased lymphocyte response (stimulation index) to a higher dose of antigenic (10 micrograms/ml) stimulation. A significantly lower lymphocyte response to antigen and mitogens was seen in HLA-DR3 positive normal healthy subjects than non-DR3 (DR3 negative) subjects. CONCLUSION: The present study suggests that HLA-DR genes/gene products may be playing an immunoregulatory role in eliciting an immune response against M. tuberculosis antigens and mitogens induced lymphocyte response in pulmonary TB patients and normal healthy subjects.     

结核分枝杆菌RD1区编码蛋白ELISPOT辅助诊断活动性结核病的应用价值

目的 比较E/C联合Rv3879c蛋白作为抗原的ELISPOT和T-SPOT.TB试剂盒,探讨其在活动性结核病诊断中的应用价值.方法 选取初治结核病患者106例作为结核组,43例肺部其它疾病患者做为疾病对照组和48例健康者做为健康对照组,应用T-SPOT.TB和ELISPOT检测受试者外周血单个核细胞的斑点形成细胞数量,同时对受试者行T研.结果 T-SPOT.TB和ELISPOT在结核病组中的敏感度分别为92.5％和93.4％,TST阴性对照组中的特异度均为91.5％,在健康者中的阳性率分别为18.8％和16.7％,且两种方法差异无统计学意义(均P＞0.05).结论 E/C联合Rv3879c蛋白作为抗原的ELISPOT能够诊断活动性结核病,并为结核感染诊断提供一定的依据.     

Tuberculosis antigen A60 serodiagnosis in tuberculous infection: Application in extrapulmonary and smear-negative pulmonary tuberculosis

Abstract An ELISA diagnostic test for tuberculosis antigen A60 (TBA60) IgG/IgM was used in a tertiary referral hospital in Taiwan. From June 1992 to December 1993, serum samples obtained from 907 patients were analyzed for TBA60 IgG and IgM titres. The final diagnosis of these patients was confirmed by microbiological study and clinical follow up for 18–24 months. Among 147 patients with active pulmonary tuberculosis, IgG was positive in 112 (76.2%), IgM was positive in 14 (9.52%). Among 90 patients with active extrapulmonary tuberculosis, IgG was positive in 53 (58.9%), IgM was positive in 9 (10%). Among 153 patients with inactive tuberculosis, IgG was positive in 28 (18.3%), IgM was positive in 1 (0.6%). Among 517 patients with nontuberculous disease, IgG was positive in 50 (9.7%), IgM was positive in 3 (0.6%). In this study population with 26% (237/907) active tuberculous infection rate, the TBA60 ELISA IgG had a diagnostic sensitivity of 69.6% and a specificity of 92.1%. These results indicate a positive predictive value of 67.9% and a negative predictive value of 89.2%. The sensitivity of IgM was 10.5% and specificity, 99.4%. The serum IgG titre had good correlation with the extent of pulmonary disease. Patients with smear-positive pulmonary TB had a higher percentage of IgG seropositivity (83.9%) than those with smear-negative pulmonary TB (70.6%) and extrapulmonary TB (58.9%). In 50 cases with active tuberculosis, follow- up examinations were carried out one month after treatment. In 18 cases with initially negative IgG and IgM titres, 13 showed elevation of serum IgG titres into positive level, one had positive seroconversion of IgM which was the only serological marker indicating active infection. Therefore, 77.8% (14/18) gained diagnostic benefit from follow-up serological examination. It was concluded that TBA60 IgG and IgM ELISA is a useful test when diagnosing tuberculosis. This test also assists in the clinical judgement of tuberculosis when used as an adjunct to symptoms and sputum smear, and for monitoring therapeutic response at the commencement of treatment.     

Tuberculosis

Tuberculosis (TB) is a disease of antiquity, caused by Mycobacterium tuberculosis, which principally affects the lungs. It is a major public-health problem, with around 9 million new cases and 2 million deaths estimated to occur each year. Patients with pulmonary TB whose sputum is smear-positive for M. tuberculosis form the main source of infection in communities. About 5%-10% of infected individuals are likely to develop symptomatic TB during their lives but the risk of developing the clinical manifestations of the disease is greatly increased by HIV co-infection. The strong association between HIV and TB in sub-Saharan Africa is responsible for the massive increase in the incidence of TB observed in that region in the last 20 years. Diagnosis of TB in resource-poor countries is largely based on sputum-smear microscopy and chest radiography, although these methods lack sensitivity or specificity, especially when used on HIV-infected patients. Effective treatment has existed for 40 years but TB-attributable mortality remains high among HIV-infected patients in Africa, who are also particularly likely to develop TB again after receiving drug treatment for the disease. In Eastern Europe it is drug resistance in the local M. tuberculosis that makes the treatment of TB relatively ineffective. The approach to TB control that is now internationally recommended is the DOTS ('directly-observed treatment, short-course') strategy, which aims to prevent the transmission of M. tuberculosis, and the related illness and death, by using combinations of anti-TB drugs to treat patients with the active disease. Unfortunately, countries in sub-Saharan Africa are falling short of the World Health Organization's targets for case detection and treatment. This failure is, in turn, making the achievement of the Millennium Development Goals for TB--to ensure that the incidence of TB is falling by 2015 and to halve the prevalence of TB and the annual number of TB-attributable deaths between 1990 and 2015--less likely. To improve the performance and impact of TB-control programmes, in the face of HIV co-infection and other constraints on DOTS, the World Health Organization has launched the revised 'Stop TB Strategy'. The new strategy, to be implemented via the Global Plan to Stop TB (2006-2015), includes intensified TB-case finding, treatment of latent TB infection with isoniazid, prevention of HIV infection, cotrimoxazole preventive therapy, and antiretroviral therapy.     

Purified protein derivative-activated type 1 cytokine-producing CD4+ T lymphocytes in the lung: a characteristic feature of active pulmonary and nonpulmonary tuberculosis

Because tuberculosis (TB) is primarily a pulmonary disease, we examined the cytokine responses of CD4(+) T lymphocytes in bronchoalveolar lavage (BAL) fluid after incubation with purified protein derivative (PPD) in human immunodeficiency virus-negative patients with TB and control subjects with nontuberculous respiratory disease. Parallel blood and BAL fluid samples from each subject were incubated with or without PPD, and the proportions of CD4(+) T lymphocytes producing interferon (IFN)-gamma or tumor necrosis factor (TNF)-alpha were measured by flow cytometry. The proportions of PPD-activated IFN-gamma- and TNF-alpha-producing CD4(+) cells were low among control subjects (median, 0.33% and 0.78%, respectively). By contrast, among patients with TB, strong IFN-gamma and TNF-alpha responses were demonstrated (median, 24.0% and 32.4%, respectively), regardless of whether the TB was pulmonary or nonpulmonary. Measurement of type 1 cytokine production by CD4(+) T lymphocytes in response to PPD in BAL fluid is a promising new diagnostic test for active TB in immunocompetent individuals.     

Integration of microscopy and serodiagnostic tests to screen for active tuberculosis.

SETTING: University of California San Diego Medical Center, USA. OBJECTIVE: To create a simple screening strategy for tuberculosis (TB) that includes antibody detection assays to improve the accuracy of microscopic examination of sputum for acid-fast bacilli (AFB smear). METHODS: Serum samples were obtained from 190 patients suspected of having active TB. TB diagnosis was established by Mycobacterium tuberculosis culture. HIV status was determined by commercial serologic tests. IgG antibody levels were measured by ELISA using purified M. tuberculosis antigens. Data from 130 randomly selected patients were used to develop a screening strategy; data from the remaining 60 patients were used for validation. RESULTS: AFB smear had 70% sensitivity and 88% specificity. In algorithms integrating single or multi-antigen ELISA with AFB smear and HIV results, the sensitivity improved over each test alone. The algorithm that included a four-antigen ELISA (38 kDa antigen, lipoarabinomannan, MPT-64 and glutamine synthase) had a sensitivity of 93% and a specificity of 76%. Compared to AFB smear, the sensitivity of the algorithm was significantly higher, while the specificity was not statistically different. CONCLUSION: This study demonstrates that a screening strategy can be created by integrating multi-antigen ELISA with AFB smear and HIV testing.     

Clinical evaluation of QuantiFERON TB-2G test for immunocompromised patients.

The usefulness of the tuberculin skin test (TST) and the QuantiFERON TB-2G (QFT-TB) test were compared in immunocompromised patients. The subjects consisted of 252 immunocompromised patients who were clinically suspected of tuberculosis (TB) infection between April 2005 and December 2006. Regarding the underlying diseases, 74 subjects had malignant diseases, 72 were undergoing immunosuppressive treatment, 52 had diabetes mellitus, 50 had chronic renal failure and four had HIV infection. While the positive rate of the QFT-TB test for the diagnosis of TB infection (TB disease or latent TB infection) was 78.1%, that of TST for TB infection was 50.0%. The QFT-TB test was significantly better than TST. However, 32 (13%) patients had an indeterminate QFT-TB result. Indeterminate findings were significantly more frequent in patients receiving immunosuppressive treatment (28%), especially with lymphocytopaenia in the peripheral blood, than in those who had other underlying diseases. While TST-positive and QFT-TB test-negative results were recognised in immunocompromised patients with bacille Calmette-Guérin vaccination or nontuberculous mycobacterial disease, TST-negative and QFT-TB test-positive results were recognised in immunocompromised patients with a past history of TB infection. It was concluded that the QuantiFERON TB-2G test is a more useful diagnostic method for tuberculosis infection than tuberculin skin test for immunocompromised patients suspected of tuberculosis disease. However, because the results of the QuantiFERON TB-2G test show an indeterminate response for patients receiving immunosuppressive treatment, especially for those with lymphocytopaenia due to severe underlying diseases, care must be taken in the interpretation of the QuantiFERON TB-2G test for these patients.     

Performance of whole blood IFN-gamma test for tuberculosis diagnosis based on PPD or the specific antigens ESAT-6 and CFP-10.

OBJECTIVE: To evaluate the QuantiFERON-TB test in BCG-vaccinated, non-BCG-vaccinated and tuberculosis (TB) patient donor groups, and to compare its diagnostic performance with that of a blood test based on the Mycobacterium tuberculosis specific antigens ESAT-6 and CFP-10. DESIGN: Analysis of the IFN-gamma responses of whole blood cells from BCG-vaccinated or non-BCG-vaccinated donors or patients with tuberculosis, stimulated with PPD, ESAT-6 or CFP-10 antigens, and evaluation of the specificity and sensitivity of the test. RESULTS: None of the non-vaccinated donors showed positive responses to M. tuberculosis-PPD, ESAT-6 or CFP-10. In BCG-vaccinated donors, 9/19 (47%) donors responded to the QuantiFERON-TB test based on M. tuberculosis-PPD, whereas 2/19 (10.5%) responded to either ESAT-6 or CFP-10. Comparable levels of sensitivity were obtained with the QuantiFERON-TB test based on M. tuberculosis-PPD (79%) and ESAT-6 or CFP-10 antigens (72%). CONCLUSION: Our results demonstrate that the whole blood test based on M. tuberculosis-PPD did not efficiently distinguish BCG-vaccinated donors from individuals with disease due to M. tuberculosis. The introduction of new recombinant antigens specific for M. tuberculosis, such as ESAT-6 or CFP-10, should increase the specificity of the whole blood test and enable discrimination between TB infection, atypical mycobacterial reactivity and reactivity due to BCG vaccination. Such a test would provide a quantum improvement over the current practice of using the tuberculin skin test for TB control and elimination.