Smear-negative Tuberculosis Patients Research Articles

Study of rapid detection of Mycobacterium Tuberculosis through GeneXpert MTB/RIF assay from acid fast bacilli smear-negative specimens in a Tertiary Care Hospital, Biratnagar Nepal

Introduction: Tuberculosis (TB) is an important public health concern around the world. It is well known that acid-fast bacilli (AFB) smear-negative TB cases are a major source of spreading TB to others when left untreated.
 Objectives: Our study aim to detect Mycobacterium tuberculosis (MTB) in AFB smear-negative samples through GeneXpert MTB/RIF assay and also to evaluate the drug resistance patterns towards Mycobacterium tuberculosis in hospitals.Methodology: This descriptive cross-sectional study was conducted among smear-negative presumptive TB patients at a tertiary care center with effect from September 2022 to September 2023 after approval from the Institutional Review Committee of the college. A convenience sampling method was used.
 Results: Out of 653 smear-negative samples, 71 (10.9%) were positive for TB and 17 (2.6%) were rifampicin resistance cases detected by GeneXpert MTB/RIF assay. The cases of tuberculosis were more in age groups between 46->60 years and least in 17-30 years of age. Pulmonary samples yielded a higher number of MTB 66 (92.95%) as compared to extra-pulmonary samples 5 (7.04%). There is an almost equal proportion of mycobacterium infection in males 37(52.11%) and females 34(47.88%). All the rifampicin resistance cases detected in our study were from pulmonary samples.
 Conclusion: Our study shows that the sensitivity of GeneXpert MTB/RIF assay is higher than AFB smear microscopy. We are missing actual TB cases while using AFB smear microscopy only. Hence the GeneXpert MTB/RIF assay is important for the rapid detection of MTB in smear-negative as well as smear-positive drug resistance MTB cases.

The elevated expression of LAG-3 on CD8+T cells correlates with disease severity of pulmonary TB

ObjectiveLymphocyte-activation gene 3 (LAG-3) plays an important role in regulating T-cell responses and inducing peripheral tolerance. Our aim in this study was to investigate the relationship between LAG-3 and active tuberculosis (ATB) and the impact of LAG-3 blockade on CD8+T cells. MethodsFlow cytometry was used to detect the expression of LAG-3 on CD4+T and CD8+T cells in the peripheral blood and bronchoalveolar lavage fluid from ATB patients and to explore the relationship between LAG-3 and ATB. ResultsThe expression of LAG-3 on CD4+T and CD8+T cells in ATB patients was increased (P < 0.001), and CD8+T cells with high expression of LAG-3 were associated with sputum culture results (P < 0.05). We further analyzed the relationship between the expression of LAG-3 in CD8+T cells and the severity of tuberculosis and found that the expression of LAG-3 on CD8+T cells in smear-positive tuberculosis patients was significantly higher than that in sputum smear-negative tuberculosis patients (P < 0.05). LAG-3 expression on CD8+T cells was negatively correlated with the presence of lung lesions (P < 0.05). After stimulation with a tuberculosis-specific antigen, the expression of LAG-3 on tuberculosis-specific CD8+T cells was also upregulated, and LAG-3-expressing CD8+T cells showed reduced production of IFN-γ, decreased activation, and lower proliferation, while the function of CD8+T cells was restored when LAG-3 signaling was blocked. ConclusionsThis study further explored the relationship between immune exhaustion caused by LAG-3 and immune escape of Mycobacterium tuberculosis and revealed that the elevated expression of LAG-3 on CD8+T cells correlates with functional defects of CD8+T cells and the severity of pulmonary TB.

Evaluation of Xpert MTB/RIF Assay, MTB Culture and Line Probe Assay for the Detection of MDR Tuberculosis in AFB Smear Negative Specimens.

The global burden of tuberculosis (TB), particularly with multidrug resistance (MDR), is escalating and has become a major health challenge. It is well known that acid-fast bacilli (AFB) smear-negative TB patients are the major source of spreading TB to healthy individuals when left untreated. Early diagnosis of TB and rapid detection of drug resistance are important for the proper management of drug-resistant TB (DR-TB). Therefore, a laboratory based cross-sectional study was conducted from July to December 2019 at the National Tuberculosis Centre, Thimi, Nepal, with the objective of evaluating the diagnostic performance of Xpert MTB/RIF assay, Mycobacterium tuberculosis (MTB) culture and line probe assay (LPA) for the detection of MDR-TB in AFB smear-negative sputum samples. We evaluated a total of 222 AFB smear-negative sputum specimens, of which 21.6% (n = 48) showed MTB positive with Xpert MTB/RIF assay and, while culturing on Lowenstein-Jensen (LJ) media, 21.2% (n = 47) were MTB culture positive. The sensitivity, specificity, PPV and NPV at 95% confidence interval of Xpert MTB/RIF assay on diagnosing M. tuberculosis from smear-negative specimens were 73% (57-84), 92% (87-96), 71% (59-81) and 93% (89-95), respectively. In addition, the sensitivity of Xpert MTB/RIF assay and LPA in detecting rifampicin resistance was 75% (42-94, 95% CI) and 91.67% (62-99, 95% CI), respectively. The current study also assessed a significant association between the occurrence of pulmonary tuberculosis with different age group, TB history and alcohol consumption. These findings indicate that Xpert MTB/RIF assay and LPA are appropriate methods for early detection and accurate diagnosis of TB and RIF mono-resistant cases.

A glimpse into the genotype and clinical importance of non tuberculous mycobacteria among pulmonary tuberculosis patients: The case of Ethiopia.

Laboratory identification of nontuberculous mycobacteria (NTM) species is not regularly performed while, they have a public health importance with a prevalence of more than 5% among pulmonary tuberculosis (PTB) patients in Ethiopia. Hence, this study aimed to identify the NTM species and their clinical significance among PTB patients. A retrospective study was conducted at the Ethiopian Public Health Institution’s (EPHI’s) national TB referral laboratory. Stored NTM isolates were genotyped using GenoType Mycobacterium CM/AS kit (Hain Life science, Germany). Data pertinent to the study was extracted from the EPHI’s database and patients’ medical records. Between January 2 & December 28 of 2017, a total of 3,834 samples were processed from 698 TB patients of whom 50% were female. Among 3,317 samples with mycobacterial culture results 7.3% were NTM and majority of them were identified from smear negative TB patients. M. simiae was the /predominant NTM among the genotyped isolates. All the studied NTM species were not clinically important however, considering the similarity of clinical and radiologic findings between NTM and MTBC infected patients, integrating NTM species identification in the routine TB laboratory diagnosis may augment clinicians’ decision particularly in DR-TB patients. Additional similar prospective study with a larger sample size is recommended. Moreover, urgent improvements on patients’ record keeping practice are required in the studied hospitals.

Persistent expression of activation markers on Mycobacterium tuberculosis-specific CD4 T cells in smear negative TB patients.

T cell activation (HLA-DR, CD-38), proliferation (KI-67), and functional (IFN-γ, TNF-α) markers have recently been shown to be useful in predicting and monitoring anti-TB responses in smear positive TB, but previous research did not characterize the activation and proliferation profiles after therapy of smear negative TB. In this study, we used polychromatic flow cytometry to assess selected PPD-specific T cell markers using fresh PBMC of smear negative and positive pulmonary tuberculosis (PTB) patients, recruited from health facilities in Addis Ababa. Levels of activation (HLA-DR, CD38) and proliferation (Ki-67) among total unstimulated CD4 T cells decreased significantly after therapy, particularly at month 6. Similarly, levels of PPD-specific T cell activation markers (HLA-DR, CD-38) were significantly lower in smear positive PTB patients following treatment, whereas a consistent decline in these markers was less apparent among smear negative PTB patients at the sixth month. After six months of standard anti-TB therapy, persistent levels of activation of HLA-DR and CD-38 from PPD specific CD4+T cells in this study could indicate that those markers have little value in monitoring and predicting anti-TB treatment response in smear negative pulmonary TB patients in Ethiopian context.

Diagnostic performance of GeneXpert MTB/RIF in detecting MTB in smear-negative presumptive TB patients

BackgroundTuberculosis (TB) is a leading cause of morbidity and mortality worldwide. Control of TB is lingering by the lack of diagnostic tests that are simple, rapid, yet accurate. Thus, smear-negative pulmonary TB often misses the diagnosis. The study evaluated the performance of GeneXpert MTB/RIF assay for the detection of Mycobacterium tuberculosis (MTB).MethodsThe study was carried out from June to December 2016 in Nepal Tuberculosis Center, Bhaktapur, Nepal. A total of 173 sputum samples were collected and processed by microscopy [Auramine-O staining and Ziehl–Neelsen (ZN) staining], followed by GeneXpert MTB/RIF assay and culture in Lowenstein-Jensen (LJ) medium.ResultsOf 173 sputum samples, 162 (93.6%) were smear-negative. Of 162 smear-negative sputum samples, 35 (21.6%) were confirmed to have MTB by culture, and 31 (19.1%) by GeneXpert MTB/RIF assay. Of 31 GeneXpert-positive samples, 25 (80.6%) were susceptible, 4 (12.9%) were resistant, and 2 (6.45%) were intermediate to rifampicin. The sensitivity, specificity, positive predictive value, and negative predictive value of GeneXpert MTB/RIF assay for smear-negative sputum samples were 74.3%, 96.6%, 86.7%, and 92%, respectively. The GeneXpert MTB/RIF has a substantial diagnostic agreement of 90.91% with culture (Cohen’s Kappa coefficient = 0.73).ConclusionThe diagnostic performance of GeneXpert MTB/RIF assay was almost on par with culture, and thus can be relied upon for MTB detection in smear-negative sputum samples.

How Do Smoking Status and Smoking Cessation Efforts Affect TB Recurrence After Successful Completion of Anti-TB Treatment? A Multicenter, Prospective Cohort Study With a 7-Year Follow-up in China.

Many important risk factors are associated with tuberculosis (TB) recurrence; among them, smoking is the most common and modifiable behavioral factor. We aimed to assess the association of smoking status and cessation support during anti-TB treatment with subsequent TB recurrence. A 7-year prospective cohort study was performed on 634 TB patients in China. The participants were grouped by smoking status at baseline. Cox proportional hazards models were applied to analyze the association between baseline characteristics and TB recurrence. The cumulative incidence of TB recurrence was estimated by Kaplan-Meier curves. Multivariable analysis showed that patients who continued smoking during anti-TB treatment were at higher risk for TB recurrence (hazard ratio = 3.45; 95% confidence interval: 1.54-7.73) than nonsmokers. Moreover, this risk remained significant even in those who stopped smoking during anti-TB treatment (hazard ratio = 2.75; 95% confidence interval: 1.47-5.14) than nonsmokers. The association between smoking and TB recurrence was stronger for smear-positive TB patients than for smear-negative TB patients. Among all the subgroups, patients who continued smoking had a higher TB recurrence rate over the 7-year follow-up than those who successfully quit during their anti-TB treatment (log-rank statistic, p < .01). With the increase in the number of cigarettes smoked daily, the TB recurrence risk also increased accordingly (log-rank statistic, p = .02). Our findings highlight the importance of incorporating effective smoking cessation intervention measures into TB services and call for continuous monitoring of TB recurrence. Among patients who continue smoking or have a history of smoking, special attention should be given to smear-positive patients and heavy smokers when monitoring recurrence. This study provides a comprehensive picture of the association of smoking behavior and cessation efforts with TB recurrence. It shows that patients who are nonsmokers have the lowest risk of recurrence and that ex-smokers have a lower risk of recurrence than current smokers. Moreover, patients who successfully quit smoking during TB treatment have a lower risk of recurrence than those who continue smoking. Health workers should provide cessation intervention, focus on TB patients with a history of smoking, and continuously monitor TB recurrence after the completion of anti-TB treatment, particularly for smear-positive TB patients.

TB-QUICK: CRISPR-Cas12b-assisted rapid and sensitive detection of Mycobacterium tuberculosis

Tuberculosis (TB) remains one of the public health problems worldwide. Rapid, sensitive and cost-effective diagnosis of Mycobacterium tuberculosis (M.tb) is critical for TB control. We developed a novel M.tb DNA detection platform (nominated as TB-QUICK) which combined loop-mediated isothermal amplification (LAMP) and CRISPR-Cas12b detection. TB-QUICK was performed on pulmonary or plasma samples collected from 138 pulmonary TB (PTB) patients, 21 non-TB patients and 61 close contacts to TB patients. Acid-fast bacillus (AFB) smear, M.tb culture and GeneXpert MTB/RIF (Xpert) assays were routinely conducted in parallel. By targeting M.tb IS6110, TB-QUICK platform could detect as low as 1.3 copy/μL M.tb DNA within 2h. In pulmonary TB samples, TB-QUICK exhibited improved overall sensitivity of 86.8% over M.tb culture (66.7%) and Xpert (70.4%), with the specificity of 95.2%. More significantly, TB-QUICK exhibited a superior sensitivity in AFB-negative samples (80.5%) compared to Xpert (57.1%) and M.tb culture (46.2%). In the detection of plasma M.tb DNA by TB-QUICK, 41.2% sensitivity for AFB-positive and 31.7% for AFB-negative patients were achieved. In conclusion, TB-QUICK exhibits rapidity and sensitivity for M.tb DNA detection with the superiority in smear-negative paucibacillary TB patients. The clinical application of TB-QUICK in TB diagnosis needs to be further validated in larger cohort.

Prevalence of pulmonary mycoses in smear-negative patients with suspected tuberculosis in the Brazilian Amazon

BackgroundPulmonary mycoses resemble clinically and radiologically chronic pulmonary tuberculosis. Studies describing the prevalence, etiology and clinical features of pulmonary mycosis are of crucial importance in the Brazilian Amazon. AimsTo estimate the frequency of pulmonary mycoses in smear-negative tuberculosis patients; to describe their demographic, epidemiological, and clinical characteristics; and to evaluate diagnostic methods. MethodsA cross-sectional study was conducted at two tuberculosis reference institutions in Amazonas, Brazil. We included 213 patients and collected clinical data, blood and induced sputum to perform serological, direct microscopy, microbiologic culture and PCR-based assays to identify infections caused by Aspergillus fumigatus, Paracoccidioides brasiliensis, Histoplasma capsulatum, Cryptococcus, and HIV. Chest computed tomography was also performed. ResultsPulmonary mycoses were diagnosed in 7% (15/213) of the cases, comprising ten aspergillosis cases, three cases of paracoccidioidomycosis and one case each of histoplasmosis and cryptococcosis. Among the patients with pulmonary mycoses, 86.7% were former tuberculosis patients. The most significant clinical characteristics associated with pulmonary mycoses were cavity-shaped lung injuries, prolonged chronic cough and hemoptysis. ConclusionsOur study confirmed the high prevalence of pulmonary mycoses in smear-negative tuberculosis patients in the Brazilian Amazon.

Urine lipoarabinomannan in HIV uninfected, smear negative, symptomatic TB patients: effective sample pretreatment for a sensitive immunoassay and mass spectrometry

Our study sought to determine whether urine lipoarabinomannan (LAM) could be validated in a sample cohort that consisted mainly of HIV uninfected individuals that presented with tuberculosis symptoms. We evaluated two tests developed in our laboratory, and used them on clinical samples from Lima, Peru where incidence of HIV is low. ELISA analysis was performed on 160 samples (from 140 adult culture-confirmed TB cases and 20 symptomatic TB-negative child controls) using 100 μL of urine after pretreatment with Proteinase K. Two different mouse monoclonal antibodies-CS35 and CHCS9-08 were used individually for capture of urine LAM. Among cases, optical density (OD450) values had a positive association with higher bacillary loads. The 20 controls had negative values (below the limit of detection). The assay correctly identified all samples (97–100% accuracy confidence interval). For an alternate validation of the ELISA results, we analyzed all 160 urine samples using an antibody independent chemoanalytical approach. Samples were called positive only when LAM surrogates—tuberculostearic acid (TBSA) and d-arabinose (d-ara)—were found to be present in similar amounts. All TB cases, including the 40 with a negative sputum smear had LAM in detectable quantities in urine. None of the controls had detectable amounts of LAM. Our study shows that urinary LAM detection is feasible in HIV uninfected, smear negative TB patients.

Combined tests with Xpert MTB/RIF assay with bronchoalveolar lavage fluid increasing the diagnostic performance of smear-negative pulmonary tuberculosis in Eastern China.

Tuberculosis (TB) remains a global public health threat. Misdiagnosis and delayed therapy of sputum smear-negative TB can affect the treatment outcomes and promote pathogen transmission. The application of Xpert MTB/RIF assay in bronchoalveolar lavage fluid (BALF) has been recommended but needs clinical evidence. We carried out a prospective study in the Nanjing Public Health Medical Center from September 2018 to August 2019. Pulmonary tuberculosis (PTB) patients were enrolled in the study if they had negative results of sputum smear. We compared the performance of Xpert MTB/RIF assay in sputum and BALF using sputum culture as the reference. In addition to this, we applied parallel tests using sputum culture, sputum-based Xpert MTB/RIF assay and BALF-based Xpert MTB/RIF assay to jointly detect smear-negative PTB using clinical diagnosis as the reference. With mycobacterial culture as the reference standard, Xpert MTB/RIF of BALF showed a higher sensitivity (14/16, 87.5%), but a relatively lower specificity (57/92, 62.0%). Xpert MTB/RIF of sputum showed relatively lower sensitivity (6/10, 60.0%) and higher specificity (63/88, 71.6%). Compared with sputum culture, Xpert MTB /RIF assay reduced the median detection time of MTB from 30 to 0 days, which significantly shortened the diagnosis time of the smear-negative TB patients. Among the combined detections, the positive detection proportion was improved with significant differences comparing with sputum culture only, from 11.1% (10/90) to 46.7% (42/90) (P < 0.05). Our study showed Xpert MTB/RIF in BALF had a better performance in detecting MTB of smear-negative patients.

Revisiting the Natural History of Pulmonary Tuberculosis: A Bayesian Estimation of Natural Recovery and Mortality Rates.

Tuberculosis (TB) natural history remains poorly characterized, and new investigations are impossible as it would be unethical to follow up TB patients without treatment. We considered the reports identified in a previous systematic review of studies from the prechemotherapy era, and extracted detailed data on mortality over time. We used a Bayesian framework to estimate the rates of TB-induced mortality and self-cure. A hierarchical model was employed to allow estimates to vary by cohort. Inference was performed separately for smear-positive TB (SP-TB) and smear-negative TB (SN-TB). We included 41 cohorts of SP-TB patients and 19 cohorts of pulmonary SN-TB patients in the analysis. The median estimates of the TB-specific mortality rates were 0.389 year-1 (95% credible interval [CrI], .335-.449) and 0.025 year-1 (95% CrI, .017-.035) for SP-TB and SN-TB patients, respectively. The estimates for self-recovery rates were 0.231 year-1 (95% CrI, .177-.288) and 0.130 year-1 (95% CrI, .073-.209) for SP-TB and SN-TB patients, respectively. These rates correspond to average durations of untreated TB of 1.57 years (95% CrI, 1.37-1.81) and 5.35 years (95% CrI, 3.42-8.23) for SP-TB and SN-TB, respectively, when assuming a non-TB-related mortality rate of 0.014 year-1 (ie, a 70-year life expectancy). TB-specific mortality rates are around 15 times higher for SP-TB than for SN-TB patients. This difference was underestimated dramatically in previous TB modeling studies, raising concerns about the accuracy of the associated predictions. Despite being less infectious, SN-TB may be responsible for equivalent numbers of secondary infections as SP-TB due to its much longer duration.

Quantitative analysis of serum-based IgG agalactosylation for tuberculosis auxiliary diagnosis.

Tuberculosis (TB) is the leading infectious cause of mortality worldwide, especially in developing countries. However, effective means for TB diagnosis, especially for bacillus-negative (Bn) TB laboratory diagnosis, are urgently needed. In the present study, serum IgG from each tuberculosis patients and healthy controls was purified using affinity chromatography. The samples were then analyzed using mass spectrometry (MS) and ultraperformance liquid chromatography (UPLC) methods. We quantitatively assessed the changes of serum IgG galactosylation in 567 human serum samples including 377 pulmonary TB patients and 190 healthy donors (HDs). We found significantly more agalactosylated (G0) vs monogalactosylated (G1) and digalactosylated (G2) N-glycans of IgG in TB patients, including smear-negative TB patients, than in HDs. The detection rate of TB diagnostic performance by MS for IgG-Gal ratio G0/(G1+G2×2) is 90.48% for bacillus-positive (Bp) and 73.16% for Bn TB patients. Further, combination of MS method with other routine laboratory TB diagnostic methods significantly increased the detection rate to 91.01%-98.39%. Similar results were observed in Mycobacterium tuberculosis (M. tb) infection mouse models. The decrease in galactosylation of IgG in TB patients was also qualitatively confirmed using specific lectin blot assay. Using the above techniques, we can discriminate the content of IgG G0 with terminal N-acetylglucosamine and IgG-Gal ratio G0/(G1+G2×2) between TB patients and HDs. Our data suggest that quantitative analysis of serum-based IgG-Gal ratio G0/(G1+G2×2) could be used for TB auxiliary diagnosis with high effectiveness and feasibility and its combination with other routine laboratory TB diagnostic methods could remarkably improve the detection rate.

Protection of healthcare workers against transmission of Mycobacterium tuberculosis in hospitals: a review of the evidence.

BackgroundEmployees in contact with infectious tuberculosis (TB) patients in healthcare facilities of low-incidence countries are still at considerable risk of acquiring TB infections. However, formal precautions recommended on the protection of healthcare workers may not only vary from country to country but also within a single country. The objective of this study was to compare current guidelines with respect to hospital infection control of TB, focusing on common shared priorities and discrepancies between sets of recommendations.MethodsFive types of procedures captured in guidelines of the World Health Organization, the United States of America, the United Kingdom and Germany are compared and the underlying evidence is discussed.ResultsUncontroversially, personal protection by respirators in the TB ward and during aerosol-generating procedures is key to reducing Mycobacterium tuberculosis exposure. However, there is no consensus on the types of masks that should be worn in different situations. Closely connected to this, there is considerable uncertainty with respect to the optimal date of removing sputum smear-negative and multidrug-resistant TB patients from isolation. Indeed, the use of notable new tools for this purpose, such as the highly sensitive PCR tests recommended by the World Health Organization for detecting TB/multidrug-resistant TB, have yet to be sufficiently incorporated into TB guidelines. Perceptions differ, too, as to whether long-term control measures for M. tuberculosis infections in healthcare workers by serial testing for latent TB infection should be established and, if so, how testing results should be interpreted.ConclusionsAlthough the current recommendations on protection of healthcare workers are otherwise homogeneous, there are considerable discrepancies that have important implications for daily practice.

Treatment outcomes and associated factors of tuberculosis patients on directly observed treatment (short course) in a tertiary hospital in Port Harcourt, Nigeria

Introduction: Although concerted efforts have been implemented to achieve tuberculosis (TB) prevention and control, varying outcomes have been reported in several quarters, despite the implementation of the directly observed treatment short-course (DOTS) strategy in virtually all parts of the world. It was considered necessary to assess the treatment outcomes of TB patients on DOTS strategy and the associated factors against the World Health Organization (WHO) target at the University of Port Harcourt Teaching Hospital (UPTH) Port Harcourt, to stimulate improvements in efforts toward patients care in the hospital and elsewhere. Methods: A health facility-based review of patients' records (January 1, 2014–December 31, 2018) at the TB Clinic of UPTH was carried out using a validated data record sheet. Patients undergoing treatment were excluded. Data were analyzed with the SPSS software version 20. Outcome frequencies were summarized, and the Pearson's Chi-square test was used to determine the association between the outcome and independent variables at P ≤ 0.05 statistical significance level. Results: Overall, 174 (25.7%) had completed treatment, 181 (26.7%) were cured, 95 (14.0%) died, 70 (10.3%) transferred out, 45 (6.6%) defaulted, 49 (7.2%) were not evaluated, 44 (6.5%) were lost to follow-up, and 8 (1.2%) failed treatment. There was a 17.6% decline in the proportion of patients that completed treatment from 35.9% in 2014 to 18.3% in 2018. On the contrary, there was an increase in the proportion of patients that were cured, from 14.1% in 2014% to 26.1% in 2018. Conclusions: The treatment success rate for TB in the hospital was below the WHO benchmark of 85% cure rate throughout the period under review. Basic reforms in the service delivery processes that specifically targets groups at risk (male patients, sputum smear-negative TB patients, and patients with human immunodeficiency virus/TB co-infection) with drug adherence counselling, defaulter tracing arrangements, and emphasis on drug-susceptibility testing are recommended to improve treatment outcomes.

Xpert® MTB/RIF associated with improved treatment initiation among patients with smear-negative tuberculosis.

BACKGROUND:Delayed diagnosis and treatment initiation of smear-negative tuberculosis (TB) patients can lead to increased morbidity and mortality, particularly among those co-infected with the human immunodeficiency virus (HIV).OBJECTIVE:To compare TB treatment initiation among smear-negative presumptive TB patients in the 6 months before and after the introduction of Xpert® MTB/RIF testing at five rural tertiary hospitals in Uganda.METHODS: Patient records of the dates and results of sputum analysis were extracted from TB laboratory registers and linked to those on treatment initiation as indicated in the TB treatment registers. The proportion of smear-negative presumptive patients who initiated anti-tuberculosis treatment was compared before and after Xpert implementation using χ2 tests. Time to treatment was analysed using Kaplan-Meier survival analysis.RESULTS:Records from 3658 patients were analysed, 1894 before and 1764 after the introduction of Xpert testing. After the introduction of Xpert, 25% (437/1764) of smear-negative presumptive TB patients underwent testing. The proportion initiated on anti-tuberculosis treatment increased from 5.9% (112/1894) to 10.8% (190/1764) (P < 0.01). However, 37% (32/87) of patients with a confirmed TB diagnosis did not initiate treatment. Time to TB treatment initiation improved from 8 to 3.5 days between the study periods.CONCLUSION:Xpert testing was associated with improved TB treatment initiation among smear-negative presumptive TB patients. Improved utilisation and linkage to treatment could improve the impact of this test on patient-centred outcomes.

Frequency of Smear-Negative Tuberculosis in Northwest Iran.

Microscopic smear examination is the most common test in tuberculosis (TB) detection. It is, however, not strong enough to identify TB in the majority of afflicted individuals; thus, a significant number of TB patients are smear negative and capable of transmitting the infection. The aim of this study was to evaluate the rate of smear-negative TB in northwest Iran. In this cross-sectional study, 329 TB-confirmed patients were evaluated through culture up to March 1, 2015, in northwest Iran. The demographic and clinical features of the smear-negative and smear-positive TB patients were compared. The χ2 test was used to compare the frequency of the variables. All the statistical analyses were conducted using SPSS, version 16 (Chicago, IL, USA). Seventy-five cases were smear negative and 254 were smear positive. Smokers, asthmatics, and extra-pulmonary TB patients were primarily among the smear-negative cases. The rate of mortality was also relatively higher among the smear-negative TB patients. Totally, 22.8% of the TB cases in northwest Iran were smear negative, with a relatively higher rate of mortality than those with positive smears. A delay in these patients' return to TB diagnosis and treatment centers increases the chance of transmission to others. This is a very sensitive issue in centers where there is no equipment for TB cultivation. Thus, it is essential to equip centers without TB cultivation facilities and to use appropriate diagnostic techniques in centers with those facilities to help rapidly detect smear-negative cases.

Transmission of Mycobacterium tuberculosis From Patients Who Are Nucleic Acid Amplification Test Negative.

Among adults with signs and symptoms of pulmonary tuberculosis (TB), recognition of transmissible TB has implications for airborne infection isolation and public health activities. Sputum smear-negative TB patients account for around one-fifth of tuberculosis transmission. The tuberculosis transmission risk of TB patients with negative results on nucleic acid amplification test (NAAT) of respiratory specimens has not been established. We sought to estimate the tuberculosis transmission risk of NAAT-negative TB patients. We retrospectively reviewed Maryland TB program data collected from 2004 to 2009, during which time NAAT using the Mycobacterium Tuberculosis Direct Test (MTD) was performed routinely. Patients with sputum Mycobacterium tuberculosis (M.tb) isolates having matching genotypes were assigned to clusters. Transmission sequence was approximated by collection order of individuals' first culture-positive specimens. Minimum transmission risks of NAAT (MTD)-negative TB patients and of smear-negative TB patients were estimated based on individuals' positions within clusters. Among 809 patients with culture-confirmed TB, M.tb genotypes were available for 782 (96.7%). For NAA-negative TB patients, the minimum transmission risk estimate was 5.1% (95% CI 0-11.4). For smear-negative TB patients, the minimum transmission risk estimate was 11.2% (95% CI 7.2-15.3). Minimum transmission risk of NAAT-negative TB patients was lower than that of smear-negative TB patients. However, transmission risk of NAA-negative TB patients appears to not be negligible.

Diagnostic performance and problem analysis of commercial tuberculosis antibody detection kits in China

BackgroundThe diagnosis of bacterium-negative pulmonary tuberculosis (TB) and extra-pulmonary TB is challenging clinically. The detection of the anti-TB antibody has an important, auxiliary, clinical diagnostic value. Therefore, TB antibody detection kits should be screened and evaluated, and the reagents with the highest sensitivity and specificity should be chosen and used clinically.MethodsThe diagnostic performance of 7 commercially available TB antibody detection kits (kits A, B, C, D, E, F and G) based on the gold immunoassay detection of immunoglobulin (Ig) G or IgM antibodies were simultaneously evaluated and compared in 62 TB cases and 56 non-TB cases in a laboratory. A retrospective analysis including 2549 cases was carried out to assess the clinical diagnosis values of bacteriological examinations and TB antibody tests (kits B and H used in the clinic).ResultsThe sensitivities of TB antibody kits A, B, C, D, E, F and G in the sera from 62 TB patients were 50.0%, 83.9%, 38.7%, 9.7%, 48.4%, 69.4% and 79.0%, respectively; the sensitivities in the sera from 24 smear-negative TB patients were 29.2%, 79.2%, 29.2%, 12.5%, 29.2%, 54.2% and 79.2%, respectively; the specificities in the sera from 56 non-TB patients were 73.2%, 25.0%, 85.7%, 96.4%, 78.6%, 78.6% and 50.0%, respectively. Of the 2549 clinically diagnosed cases, there were 1752 pulmonary TB cases, 505 extra-pulmonary TB cases, 87 old pulmonary TB cases and 205 non-TB cases. The positive results for smear, culture, TB antibody kit B and kit H in pulmonary TB cases were 39.8% (543/1365), 48.6% (372/765), 45.8% (802/1752) and 25.2% (442/1752), respectively; the results in extra-pulmonary TB cases were 3.4% (6/178), 5.8% (4/69), 35.4% (179/505), and 11.3% (57/505), respectively; the results in old pulmonary TB cases were 0% (0/64), 0% (0/30), 32.2% (28/87), and 9.2% (8/87), respectively; and the results in non-TB cases were 0% (0/121), 0% (0/56), 21.5% (44/205), and 2.4% (5/205), respectively. Of 624 smear-positive and/or culture-positive pulmonary TB cases, the sensitivities of antibody test kits B and H were 53.0% and 36.4%, respectively. Of 901 smear-negative and/or culture-negative pulmonary TB cases, the sensitivities of antibody test kits B and H were 42.5% and 19.0%, respectively. The positive rate of antibody detection in the bacterium-positive pulmonary TB cases was significantly higher than that in the bacterium-negative pulmonary TB cases (P < 0.05).ConclusionsThe colloidal gold-labeled TB antibody IgG detection assay is a simple, rapid and economical method that provides a better clinical auxiliary diagnosis value on TB, especially in smear-negative pulmonary TB and extra-pulmonary TB. The production, quality control, screening and evaluation of antibody detection kits are very important for its clinical application.

Factors associated with negative T-SPOT.TB results among smear-negative tuberculosis patients in China

We compared the positive rates of T-SPOT.TB and bacterial culture in the smear-negative PTB, and analyzed the factors affecting the results of negative T-SPOT.TB and bacterial culture. Retrospective evaluation of data from smear-negative PTB patients who underwent T-SPOT.TB and bacterial culture were done. The agreement and concordance were analyzed between T-SPOT.TB and bacterial culture. Multivariable logistic regression analysis was used to explore the factors associated with positive results of T-SPOT.TB and bacterial culture in smear-negative PTB. 858 eligible smear-negative PTB patients were included in the study. The agreement rate was 25.6% (22.7~28.5%) between T-SPOT.TB and bacterial culture in smear- negative PTB patients. The positive rate of T-SPOT.TB was higher than that of bacterial culture in smear-negative PTB patients (p < 0.001). There were nearly no concordance between T-SPOT.TB and bacterial culture (p > 0.05). Using multivariable logistic regression analysis we found that older age ≥ 60 years (OR = 0.469, 95% CI: 0.287–0.768) and decreased albumin (OR = 0.614, 95% CI: 0.380–0.992) were associated with negative diagnostic results of T-SPOT.TB in smear-negative PTB patients. Female (OR = 0.654, 95% CI: 0.431–0.992) were associated with negative diagnostic results of bacteria culture in smear-negative PTB patients. Our results indicated that the older age and decreased albumin were independently associated with negative T-SPOT.TB responses.