AFB Smear Microscopy Research Articles

IJCM_276A: Determinants of Delayed Sputum Conversion among Tuberculosis Patients in Malappuram District: A Case Control Study

Background: Treatment of drug-sensitive TB consists of an intensive phase of 2 months followed by a continuation phase of 4 months. After completion of intensive phase of therapy, sputum AFB smear microscopy is repeated and presence of smear conversion is suggested as a significant early predictor of treatment effectiveness. Delay in sputum conversion will lead to prolongation of the period of time that patients remain contagious. Objectives: To study the determinants of delayed sputum conversion among Tuberculosis patients in Malappuram district Methodology: A Case control study was conducted among tuberculosis patients residing in Malappuram district of Kerala and registered under NTEP in District Tuberculosis Centre (DTC), Manjeri, Malappuram. After satisfying inclusion and exclusion criteria, 90 tuberculosis patients who failed to achieve sputum smear negativity after completion of 2 months of intensive phase multi drug therapy were taken as cases. Another 90 tuberculosis patients those who achieved sputum smear negativity after completion of 2 months of intensive phase therapy were selected as control group. Data was collected by interview method. Results: Patients with lower socio-economic status (OR = 3.59, 95% CI 1.92- 6.73), low BMI or underweight (OR = 1.98, 95% CI 1.1 - 3.6), multiple symptoms (OR= 5.50, 95% CI 1.98 - 15.28), increased duration of symptoms (OR=4.54, 95% 2.24-9.19), co-morbid condition of diabetes mellitus (OR = 2.25, 95% CI 1.24 - 4.09) are at statistically significant risk of delay in sputum smear conversion after intensive phase of anti-tubercular therapy. Conclusion: Patients with lower socio-economic status, low BMI or underweight, multiple symptoms, increased duration of symptoms, co-morbid condition of diabetes mellitus are at statistically significant risk of delay in sputum smear conversion after intensive phase of anti-tubercular therapy. Treating physicians and public health experts should give special attention to TB patients with these risk factors.

Comparative analysis of five etiological detecting techniques for the positive rates in the diagnosis of tuberculous granuloma

PurposeTo examine the relationship between the positive rate and types of necrosis in pathological examinations of tuberculosis granulomas with necrosis, to improve the detection rate of positive cases. MethodsSpecimens from 381 patients were collected in Wuhan Pulmonary Hospital from Jan 2022 to Feb 2023. The samples were examined using various methods such as AFB smear microscopy, mycobacterial culture, PCR, SAT-TB, and X-pert MTB/RIF rapid molecular detection. ResultThere were 3 types of necrosis. Including 270 cases of caseous necrosis, 30 cases of coagulation necrosis, and 76 cases of an abscess. Five cases were non-necrotizing granulomas.In the pathological specimen testing for tuberculosis, five detection techniques were used and their positive rates detected in descending order were X-pert, TBDNA, SAT-TB, tuberculosis culture, AFB. Comparison between different examinations in the group: X-pert had the highest positive rate in each group, and it was significantly higher than TBDNA (P < 0.01) in caseous necrosis specimens. Compared with the same examination between the groups, the detection rates of X-pert and TBDNA in abscess and caseous necrosis specimens were significantly higher than in coagulation necrosis specimens (P < 0.01). ConclusionThe positive rates of the five etiological detection techniques in tuberculous granuloma with different types of necrosis were quite different. The specimens of caseous necrosis or abscess could be selected for detection, and X-pert had the highest positive rate.

Detection of Mycobacterium tuberculosis Complex in Sputum Samples Using Droplet Digital PCR Targeting mpt64.

Tuberculosis (TB) is one of the top 10 causes of death worldwide. It is challenging to find methods of diagnosis of active pulmonary TB that are sensitive enough to detect cases for proper treatment before unintentional transmission. Droplet digital PCR (ddPCR) is a highly sensitive method to detect genetic material of pathogens, but it has rarely been used for diagnosis of TB. This study compared the sensitivity of ddPCR with that of GeneXpert and AFB smear microscopy in 180 leftover sputum samples from patients suspected of having TB on the basis of clinical symptoms and radiography. Absolute quantification of copy numbers of MTB-specific genes was possible using ddPCR targeting the mpt64 gene. Among the 180 samples, 41.1% were diagnosed as having TB using ddPCR. The sensitivities of AFB smear microscopy, GeneXpert and ddPCR were 41.9%, 82.4% and 100%, respectively. AFB smear microscopy and GeneXpert both had a specificity of 100%, and the specificity of ddPCR was 95.3%. The accuracy of ddPCR (97.2%) is higher than that of GeneXpert (92.7%). This robust ddPCR system could potentially be used as a method for early diagnosis of TB.

Comparison of Genexpert MTB/RIF Assay and AFB Smear Microscopy in Diagnosis of Pulmonary Tuberculosis among HIV Patients at a Tertiary Care Hospital

Introduction: Tuberculosis (TB) has been the most common acute opportunistic infection in HIV positive patients and accounts for more than half of all AIDS cases in underdeveloped nations. Hence, rapid laboratory diagnosis of M. tuberculosis is needed for vulnerable patients. Methodology: In this study, 72 sputum samples were collected from ART-naive and patients using ART for 6 months. The samples were tested with the GeneXpert MTB / RIF assay to diagnose TB and drug resistance and AFB smear microscopy as per NTP guidelines. Results: Among 72 sputum samples studied, males were more diagnosed with TB than females. People aged 25-56 years were more infected with HIV-TB co-infection. Four patients (5.56%) were found to be TB positive with both techniques, 7 (9.72%) were GeneXpert MTB/RIF positive but smear-negative and 61 patients (84.72%) were negative with both methods. The positivity for MTB detected for GeneXpert MTB/RIF method in females was 3 (15%) and the males were 8 (15.38%), while for the ZN staining method the positivity in females was 2 (10%) and the males were 2 (3.85%). The GeneXpert MTB/RIF assay was also capable of detecting TB in smear-negative cases. Conclusion: This study showed that the GeneXpert MTB/RIF assay is an effective tool for the early diagnosis of TB among HIV patients as compared to AFB smear staining method.

Detection rate of pulmonary tuberculosis by direct and concentrated microscopy techniques with Lowenstein-Jensen Culture as standard: South-South Nigeria Scenario

Objective: This study seeks to identify a more sensitive smear microscopy method for the detection of Mycobacterium tuberculosis in low-resource centers. Materials and methods: One hundred and forty sputum specimens were collected and direct smears were prepared as the specimen was submitted. The specimens were afterward digested/decontaminated using the modified Petroff’s method. Both smear methods were stained by the Ziehl-Neelsen technique and examined. All specimens (direct and concentrated) were cultured on a Lowenstein-Jensen medium and results were considered the gold standard to calculate sensitivity. Results: Out of 140 specimens, 27 (19%) and 34 (24%) were positive by direct and concentrated methods respectively. The number of culture positives by the direct and concentrated method was 26 (19%) and 31(22%) respectively. The sensitivity of direct and concentrated methods was 92.3% and 100% respectively. The negative culture and contamination rate was minimum with the concentrated method. The diagnostic accuracy of direct and concentrated methods was 88.6% and 97.1%. Conclusion: In summary, results showed concentrated techniques were able to detect more true positive Mycobacterium tuberculosis than the direct smear method. Therefore, the study region with AFB smear microscopy can utilize the concentrated smear method for AFB smear microscopy to improve the case-finding strategy.

A Comparative Study between AFB Smear Microscopy (Ziehl-Nelsen) and Gene-Expert Technique in the Diagnosis of Tuberculosis

611 samples were collected and tested for AFB using the Zeihl-Neelsen technique. Of the 611 samples tested, 525 were negative with Ziehl-Neelsen AFB smear microscopy. The 525 negative samples were tested using the genexpert technique. 53 out of the 525 samples were positive with genexpert with a percentage positivity rate of 10.1%. The data analysis was done using the student’s t-test. There was a significant difference between the sensitivity of Ziehl-neelsen technique when compared with genexpert technique (t= 3.32; p&lt; 0.05). Hence, there was a demonstrated increase in laboratory based TB detection using Xpert MTB/Rif compared to smear microscopy (ziehl-neelsen).

Costs and cost-effectiveness of Gene Xpert compared to smear microscopy for the diagnosis of pulmonary tuberculosis using real-world data from Arsi zone, Ethiopia.

BackgroundEarly diagnosis and treatment are one of the key strategies of tuberculosis control globally, and there are strong efforts in detecting and treating tuberculosis cases in Ethiopia. Smear microscopy examination has been a routine diagnostic test for pulmonary tuberculosis diagnosis in resource-constrained settings for decades. Recently, many countries, including Ethiopia, are scaling up the use of Gene Xpert without the evaluation of the cost and cost-effectiveness implications of this strategy. Therefore, this study evaluated the cost and cost-effectiveness of Gene Xpert (MTB/RIF) and smear microscopy tests to diagnosis tuberculosis patients in Ethiopia.MethodsWe compared the costs and cost-effectiveness of tuberculosis diagnosis using smear microscopy and Gene Xpert among 1332 patients per intervention in the Arsi zone. We applied combinations of top-down and bottom-up costing approaches. The costs were estimated from the health providers’ perspective within one year (2017–2018). We employed “cases detected” as an effectiveness measure, and the incremental cost-effectiveness ratio was calculated by dividing the changes in cost and change in effectiveness. All costs and incremental cost-effectiveness ratio were reported in 2018 US$.ResultsThe unit cost per test for Gene Xpert was $12.9 whereas it is $3.1 for AFB smear microscopy testing. The cost per TB case detected was $77.9 for Gene Xpert while it was $55.8 for the smear microscopy method. The cartridge kit cost accounted for 42% of the overall Gene Xpert’s costs and the cost of the reagents and consumables accounted for 41.3% ($1.3) of the unit cost for the smear microscopy method. The ICER for the Gene Xpert strategy was $20.0 per tuberculosis case detected.ConclusionUsing Gene Xpert as a routine test instead of standard care (smear microscopy) can be potentially cost-effective. In the cost scenario analysis, the price of the cartridge, the number of tests performed per day, and the life span of the capital equipment were the drivers of the unit cost of the Gene Xpert method. Therefore, Gene Xpert can be a part of the routine TB diagnostic testing strategy in Ethiopia.

To Study the Role of Cartridge-Based Nucleic Acid Amplification Test (CBNAAT) in Early Diagnosis of Extra Pulmonary Tuberculosis.

Diagnosing EPTB is difficult as various clinical presentations are seen with paucibacillary nature of the disease. Maurya AK et al. (J Postgrad Med 58(3):185-189) AFB smear hasn't been much effective in diagnosing of EPTB. Tuberculosis of head and neck diagnosis can be missed due to large number of smear negative cases, leading false negative cases increase. CBNAAT is cartridge-based nucleic acid amplification test which detects the presence of TB bacilli this study we have examined the effectiveness of CBNAAT for diagnosing EPTB with cervical lymphadenitis and compared with Sputum AFB Microscopy smear. Aims and objective 1.To study the role of cartridge-based nucleic acid amplification test (CBNAAT) in early diagnosis of extra pulmonary tuberculosis. 2 Comparative analysis of CBNAAT with AFB smears in EPTB. Type of Study Descriptive retrospective observational study was done at the department of ENT and Head & surgery, A.B.V. Govt medical college, Vidisha, M.P, India. Result Out of 184 patients 43 samples were AFB smear positive and 141 were negative. In CBNAAT 88 out of 184 and 96 were found to be negative.32 patients were negative on Sputum microscopy AFB analysis but found to be positive on CBNAAT. Sensitivity of CBNAAT was 86% AFB 64%, Specificity of CBNAAT, AFB is 91% and 89% respectively. Our study finds that CBNAAT is much more effective in diagnosis of EPTB with cervical lymphadenitis when compared to AFB smear microscopy alone.

Diagnostic yield of post-bronchoscopy sputum for diagnosing pauci-bacillary pulmonary tuberculosis

Background A few studies have mentioned that post-bronchoscopy sputum (PBS) could improve the diagnostic yield in pauci-bacillary pulmonary tuberculosis (PTB). Therefore, we evaluated the diagnostic yield of PBS for diagnosing pauci-bacillaryPTB. Methods Clinical data of immunocompromised adult patients with pauci-bacillary PTB were retrospectively retrieved at a tertiary hospital in Seoul, South Korea over a 5-year period. We analyzed patients who underwent bronchoscopy examinations for diagnosing pauci-bacillary PTB. Results Ninety patients were finally analyzed. Of these patients, 76 patients were tested with PBS. Six (8%) of these patients had positive results on AFB smear of PBS alone. Additionally, 52 patients (68%) had positive results on mycobacterial culture and 12 (16%) had positive results on mycobacterial culture of PBS exclusively. Therefore, in this study population, a total of 18 patients (20%) were finally diagnosed as having PTB with PBS results only, even though AFB smear microscopy and culture of other specimens had negative results. Conclusions PBS could improve the diagnostic yield by 20% when diagnosing pauci-bacillary PTB. In addition, about 8% of the patients could be diagnosed rapidly because of AFB smear microscopy positivity for PBS. Therefore, PBS use should be considered as a complementary diagnostic approach in patients with suspected pauci-bacillary PTB.

Evaluation of BAL versus sputum specimen for the diagnosis of pulmonary tuberculosis in sputum AFB smear negative patients- retrospective study at PIMSR, Gujarat

Aims and Objective: Early diagnosis of smear negative tuberculosis is a significant challenge in control of tuberculosis. The present retrospective study was done on sputum and BAL samples of the same patients for better diagnosis of pulmonary tuberculosis. Material and Methods: A total of 1000 (700 sputum and 300 BAL) specimens were processed to rule out tuberculosis in suspected cases during the period of August 2015 to March 2018. The result of sputum as well as BAL specimens from 300 same patients were examined for ZN staining and GeneXpert tests. The samples of sputum and BAL were processed as per the standard guidelines. Results: Total of 1000 specimens (700 sputum & 300 BAL) were considered for the results. Out of 1000 specimens 300 patients had submitted both sputum as well as BAL specimens. These 300 specimens were analyzed for comparative results. Out of 300 common samples, 109 (36.3%) sputum and 136 (45%) BAL samples are positive by ZN stain. Whereas, Out of 300 common samples, 149 (49.6%) sputum and 170 (56.6%) BAL samples are positive by GeneXpert method. Out of 149 common specimens that were positive by GeneXpert, 5(3.3%) were found to be Rifampicin resistant. Conclusion: Incidence of MDR TB is 3.3% in our hospital. BAL was found to be superior specimen to sputum for the diagnosis of ZN smears negative pulmonary TB. Sensitivity and specificity of GeneXpert is higher than AFB smear microscopy. Keywords: Sputum, BAL, GeneXpert, MDR-TB (Multidrug Resistance Tuberculosis).

Active household contact screening for tuberculosis and provision of isoniazid preventive therapy to under-five children in Afghanistan.

This observational study analyzed the performance of the National TB Control Program (NTP) in Afghanistan in household contact screening from 2011 to 2018 and its use as an entry point for isoniazid preventive therapy (IPT), as well as the IPT completion rates for children under age five. From 2011 to 2018, the Afghanistan NTP released guidelines for passive and active contact screening of bacteriologically confirmed TB cases. Health workers were trained in contact screening. Presumptive TB cases gave sputum for AFB smear microscopy; other diagnostics were used if patients could not produce sputum. Children under five (excluding those with active TB) were treated for latent TB infection. We calculated the yield and the number needed to screen and number needed to test to find a case of TB, as well as the rates of IPT initiation and completion. From 2011 to 2018, 142,797 bacteriologically confirmed TB cases were diagnosed in Afghanistan. The number of household members eligible for screening was estimated to be 856,782, of whom 586,292 (81%) were screened for TB and 117,643 (20.1%) were found to be presumptive TB cases. Among the cases screened, 10,896 TB cases (all forms) were diagnosed (1.85%, 95% CI 1.82-1.89), 54.4% in females. The number needed to screen to diagnose a single case of TB (all forms) was 53.8; the number needed to test was 10.7. Out of all children under five, 101,084 (85.9%) were initiated on IPT, and 69,273 (68.5%) completed treatment. Program performance in contact screening in Afghanistan is high, at 81%, and the yield of TB is also high-close to 10 times higher than the national TB incidence rate. IPT initiation and completion rates are also high as compared to those of many other countries but need further improvement, especially for completion.

Comparison of Led Fluorescent Microscopy and the Gene Xpert MTB/RIF Assay in Diagnosis of Pulmonary and Extrapulmonary Tuberculosis

Objectives: The objective of this study was to evaluate Gene Xpert MTB/RIF Assay and anid fast staining (AFB) for rapid detection of Mycobacterium tuberculosis in specimen of patients suspected of pulmonary tuberculosis (PTB) and extra pulmonary tuberculosis (EPTB).&#x0D; Methods: A comparative cross-sectional study of 400 samples (PTB-365 and EPTB-35) of patients visiting National Tuberculosis Centre (NTC) was conducted from July 2018 to December 2018. Gene Xpert MTB/ RIF Assay, smear microscopy were performed under standard guideline inside biosafety cabinet class II. The result obtained from both the tests were analyzed using SPSS 20.0 software and Excel 2019.&#x0D; Results: Of the total samples, 18% (72/400) and 39% (156/400) were positive by AFB smear microscopy and Xpert MTB/RIF assay respectively. Prevalence of MTB positive was highest in the age group 35-44 years, 33 cases (17.74%) were detected in total, with a male to female ratio of 2.3:1. Pleural fluid, pus, and CSF fluid also yielded positive results with the Gene Xpert MTB/RIF assay accounting 1.28%, 0.64% and 1.28% of MTB positive case respectively. Rifampicin resistance was observed in 1.28% of the cases.&#x0D; Conclusion: The key findings of this study suggest that Gene Xpert test should be implemented as primary diagnostic test for PTB and EPTB.

A study of Revised National Tuberculosis Control Programme quality assurance of sputum microscopy at tuberculosis unit

Background: Since, Revised National Tuberculosis Control Programme (RNTCP) relies on sputum microscopy for diagnosis, categorization of patients and assessment of treatment, the credibility, success and sustainability of the programme depends on the lab networks. The objectives of this study were to Quality assurance of Sputum Microscopy under RNTCP in Tuberculosis Unit.Methods: A cross-sectional analytic study was conducted at DMC ML Chest hospital, DMC LLRM Hospital and DMC ESI Hospital. On-site evaluation was conducted once a month by Senior Tuberculosis Lab. Supervisor (STLS) of the DMCs (First Controller). This visit included a comprehensive assessment of laboratory safety procedure, conditions of equipment as well as technical components of AFB smear microscopy which includes prepare, staining and reading of smears. This also included examination of five positive and five negative smears in unblinded manner, to observe the quality of smear and staining as well as condition of microscope at each DMCs. A check list prepared for collection and analysis of standard data to point out remedial action.Results: The overall slide positivity rate (SPR) was 20.17% and 23.99% for ZN-stained slides and fluorescence stained slides respectively. On-site evaluation of all DMCs revealed a good result except of DMC- LLR in maintenance of microscope and well organized and clean working areas. The overall concordance for RBRC slides result of ZN-stained slides was 98.64% and overall discordance was 1.35%. The overall agreement in the re-reading of fluorescent stained slides was 100%. The overall sensitivity, specificity, positive predictive value and negative predictive value of blinded re-checked fluorescence stained slides were 100% each respectively.Conclusions: The overall performance of all DMCs is acceptable.

Exploration of some new secretory proteins to be employed for companion diagnosis of Mycobacterium tuberculosis

Tuberculosis (TB) is a highly infectious disease and its early and precise diagnosis is essential to reduce morbidity and mortality of patients. Since the routine diagnostic tests (like Monteux, AFB smear microscopy, chest X-Ray) do not give infallible results, additional tests are always recommended. Therefore to address the concerns about non-specificity of the present battery of diagnostic tests, we have attempted to analyze some unique secretory antigens which could be able to identify the stage specific infection of MTB. In this study, we have used recombinant proteins CFP-10, ESAT-6, Ag85 A, Ag85B, Ag85C, PE3, PE4 and Mycp1 to eliminate heterogeneity and cross reactivity in clinical diagnosis. Amplified genes were cloned and over-expressed in Escherichia coli BL21 (DE3). The recombinantly purified proteins were used as antigens against 158 sera samples of TB patients. Secretory proteins showed better response than the PPD control. Among all the used antigens PE3 and PE4 proteins showed better reactivity levels among all the groups of TB patients. The secretions of CFP-10 and ESAT-6 were also higher as compared to other secretory proteins like Ag85 A, Ag85B, Ag85C and MycP1.The clinical use of these newly identified secretory antigens could be of significant value for the confirmatory, rapid, simple and low-cost diagnosis of TB patients.

Diagnosis of Genial Tuberculosis by PCR and other conventional methods

Female Genital Tuberculosis is a unique diagnostic challenge among the infertile population in countries where TB poses a high epidemiological risk. Early diagnosis and effective management is crucial to secure the reproductive organs from irretrievable damage. This cross sectional study was done between April 2011 to March 2012 in the Department of Microbiology and Immunology, Bangabandhu Sheikh Mujib Medical University in collaboration with National Tuberculosis Reference Laboratory and TB laboratory of International Centre for Diarrhoeal Disease Research, Bangladesh to compare the different laboratory tests on endometrial tissue for the diagnosis of genital tuberculosis. Laparoscopic endometrial tissue biopsies of 91 infertile women with clinical suspicion of Genital Tuberculosis were subjected to AFB smear microscopy, culture in Lowenstein Jensen media, histopathology and PCR assay. Two primers - mpt64, IS6110 were used as target for Mycobacterial DNA. Among the endometrial tissue samples of 91 infertile cases, AFB smear was positive in 43 (47%) cases, 8 (7.6%) cases was positive in culture; while PCR was positive in 36 (42.4%) cases. None of the cases were positive for epithelioid granulomatous lesions. PCR was found positive in 33% of smear negative cases and 35% of culture negative cases while PCR was found negative in 53.4% of smear positive cases and 12.5% of culture positive cases. Use of both AFB smear microscopy and PCR assay enhances the detection rate of GTB.Bangladesh J Med Microbiol 2014; 08 (02): 03-07

Diagnostic usefulness of T-cell based assays for tuberculous meningitis in HIV-uninfected patients

Early diagnosis and treatment of tuberculous meningitis (TBM) is essential for a positive outcome, but sensitive, specific, and rapid diagnostic tests for TBM are lacking. We evaluated the diagnostic utility of enzyme-linked immunosorbent spot (ELISPOT) assays in HIV-uninfected patients with suspected TBM. All HIV-uninfected patients with suspected TBM were prospectively enrolled at a tertiary care hospital in an intermediate TB-burden country, during a 6-year period. ELISPOT assays were performed on peripheral blood mononuclear cells (PBMC) and cerebrospinal fluid-mononuclear cells (CSF-MC). Of the 276 evaluable patients, 90 (33%) were classified as having TBM (30 definite cases, 19 probable, and 41 possible), and 186 (67%) as having non-TBM. When comparing definite TBM versus non-TBM, the sensitivity and specificity of the PBMC ELISPOT assay (≥6 spots; manufacturer's recommended cut-off) for diagnosing TBM were 96% (95% CI, 82-100) and 58% (95% CI, 50-66), respectively. The CSF-MC ELISPOT assay (≥38 spots; receiver operating characteristic [ROC]-derived cut-off) was a useful rule-in test with specificity of 95% (96% CI, 90-98). Its sensitivity was 68% (95% CI, 45-86), which was superior those of AFB smear microscopy (14%; P < 0.001) and CSF Mycobacterium tuberculosis PCR (41%; P = 0.07). Combining this assay with M. tuberculosis PCR, clinical score, and both together increased sensitivity to 86%, 91%, and 95%, respectively, while retaining about 95% specificity. The CSF-MC ELISPOT assay appears to be a rapid and accurate rule-in test for the diagnosis of TBM and a useful adjunct for diagnosing TBM in HIV-uninfected patients.

Performance of the WHO 2011 TB Symptom Screening Algorithm for Pulmonary TB Diagnosis among HIV-Infected Patients in Gondar University Referral Hospital, Ethiopia.

The new WHO 2011 guidelines on TB screening among HIV-infected individuals recommend screening using four TB symptoms (current cough, fever, weight loss, and night sweats). This study aimed to assess the performance of WHO 2011 TB symptom screening algorithm for diagnosing pulmonary TB in HIV patients and identify possible risk factors for TB. Institutional based cross-sectional study was conducted from February 2012 to November 2012. A total of 250 HIV-infected patients aged ≥18 years visiting the University of Gondar Hospital, ART clinic, were enrolled. Information about WHO TB clinical symptoms and other known risk factors for TB was collected using structured questionnaire. Spot-morning-spot sputum samples were collected and direct AFB microscopy, sputum culture, and RD9 molecular typing were performed. Statistical data analysis was performed using SPSS Version 20.0 software. Of 250 study participants, fever was reported in 169 (67.6%), whereas cough and night sweats were reported in 167 (66.8%) and 152 (60.8%), respectively. A total of 11 (4.4%) TB cases were identified. Of these, 82% (9/11) TB patients reported cough, so that the negative predictive value was 98%. In addition, 66% (158/239) TB negative patients reported cough, so that positive predictive value of cough was 5%. According to the new WHOTB symptom screening algorithm, out of 250 HIV-infected persons, 83% (5/6) have been investigated by TB symptom screening and AFB smear microscopy. Therefore, the 2011 WHO TB symptom screening tool for the diagnosis of pulmonary TB is likely to reduce the diagnostic delay and lower TB morbidity and mortality rate particularly in HIV prevalent settings.

Is a composite reference standard (CRS) an alternative to culture in assessment and validation of a single tube nested in-house PCR for TB diagnosis?

IntroductionDelay in diagnosis of paucibacillary extra pulmonary tuberculosis (TB) and of smear negative TB has hampered the efforts taken by Control Programs to curb its spread. Better efforts to control spread of TB require more accurate and rapid diagnostic test. AimsTo facilitate early diagnosis of TB directly from clinical specimens, we have standardized and validated the use of a single tube in-house nested PCR in comparison against culture and composite reference standard (CRS). MethodsSingle tube nested PCR was performed using primers targeting Insertion Sequence (IS) 6110 of Mycobacterium tuberculosis complex. Microbiological techniques includes AFB smear microscopy, and cultivation on solid egg-based medium (Löwenstein–Jensen [LJ]) and on liquid culture medium using BACTEC MGIT 960 system, BD Microbiology Systems. ResultsThe sensitivity and specificity of PCR against culture was observed to be 89.7% [95% CI: 84.1–93.5] and 73.1% [95% CI: 67.4–78.1] respectively and that against CRS criteria was 80.2% [95% CI: 75.1–84.5] and 97.1% [95% CI: 92.9–98.9] respectively. PCR showed 100% [111/111, 95% CI: 97–100] sensitivity for smear positive specimens. For smear negative specimens sensitivity and specificity of PCR against culture was observed to be 78.4% [69/88, 95% CI: 68.4–86.5] and 77.3% [204/264, 95% CI: 71.7–82.2] respectively and that against CRS was 68.1% [124/182, 95% CI: 60.8–74.8] and 97.1% [165/170, 95% CI: 93.3–99] respectively. ConclusionCRS criteria were observed to be better than culture for assessing the diagnostic accuracy of PCR test.

The Diagnostic Performance of a Single GeneXpert MTB/RIF Assay in an Intensified Tuberculosis Case Finding Survey among HIV-Infected Prisoners in Malaysia

BackgroundDelays in tuberculosis (TB) diagnosis, particularly in prisons, is associated with detrimental outcomes. The new GeneXpert MTB/RIF assay (Xpert) offers accurate and rapid diagnosis of active TB, but its performance in improving case detection in high-transmission congregate settings has yet to be evaluated. We assessed the diagnostic accuracy of a single Xpert assay in an intensified case finding survey among HIV-infected prisoners in Malaysia.MethodsHIV-infected prisoners at a single site provided two early-morning sputum specimens to be examined using fluorescence smear microscopy, BACTEC MGIT 960 liquid culture and a single Xpert. The sensitivity, specificity, negative and positive predictive values of Xpert were calculated relative to gold-standard results using MGIT 960 liquid culture. Relevant clinical and demographic data were used to examine correlates of active TB disease.ResultsThe majority of enrolled subjects with complete data (N=125) were men (90.4%), age <40 years (61.6%) and had injected drugs (75.2%). Median CD4 lymphocyte count was 337 cells/µL (IQR 149-492); only 19 (15.2%) were receiving antiretroviral therapy. Of 15 culture-positive TB cases, single Xpert assay accurately detected only eight previously undiagnosed TB cases, resulting in a sensitivity, specificity, positive predictive value and negative predictive value of 53.3% (95% CI 30.12-75.2%), 100% (95% CI 96.6-100%), 100% (95% CI 67.56-100%) and 94.0% (95% CI 88.2-97.1%), respectively. Only 1 of 15 (6.7%) active TB cases was smear-positive. The prevalence (12%) of undiagnosed active pulmonary TB (15 of 125 prisoners) was high and associated with longer duration of drug use (AOR 1.14, 95% CI 1.03-1.26, for each year of drug use).ConclusionsSingle Xpert assay improved TB case detection and outperformed AFB smear microscopy, but yielded low screening sensitivity. Further examination of the impact of HIV infection on the diagnostic performance of the new assay alongside other screening methods in correctional settings is warranted.

Survival among Patients with HIV Infection and Smear-Negative Pulmonary Tuberculosis - United States, 1993–2006

BackgroundIn patients with HIV and tuberculosis (TB) in resource-constrained settings, smear-negative disease has been associated with higher mortality than smear-positive disease. Higher reported mortality may be due to misdiagnosis, diagnostic delays, or because smear-negative disease indicates more advanced immune suppression.MethodsWe analyzed culture-confirmed, pulmonary TB among patients with TB and HIV in the United States from 1993–2008 to calculate prevalence ratios (PRs) for smear-negative disease by demographic and clinical characteristics. Allowing two years for treatment outcome to be reported, we determined hazard ratios (HRs) for survival by smear status, adjusted for significant covariates on patients before 2006.ResultsAmong 16,710 cases with sputum smear results, 6,739 (39%) were sputum smear-negative and 9,971 (58%) were sputum smear-positive. The prevalence of smear-negative disease was lower in male patients (PR: 0.89, 95% confidence interval [CI]: 0.86–0.93) and in those who were homeless (PR: 0.92, CI: 0.87–0.97) or used alcohol excessively (PR: 0.91, CI: 0.87–0.95), and higher in persons diagnosed while incarcerated (PR: 1.20, CI: 1.13–1.27). Patients with smear-negative disease had better survival compared to patients with smear-positive disease, both before (HR: 0.82, CI: 0.75–0.90) and after (HR: 0.81, CI: 0.71–0.92) the introduction of combination anti-retroviral therapy.ConclusionsIn the United States, smear-negative pulmonary TB in patients with HIV was not associated with higher mortality, in contrast to what has been documented in high TB burden settings. Smear-negative TB can be routinely and definitively diagnosed in the United States, whereas high-burden countries often rely solely on AFB-smear microscopy. This difference could contribute to diagnostic and treatment delays in high-burden countries, possibly resulting in higher mortality.