Acid-fast Bacilli Smear Microscopy Research Articles

Preventing Infectious Pulmonary Tuberculosis Among Foreign-Born Residents of the United States.

We described risk factors associated with infectious tuberculosis (TB) and missed TB-prevention opportunities in foreign-born US residents, who account for almost two thirds of the nation's TB patients. In a cross-sectional study at 20 US sites of foreign-born persons diagnosed with TB in 2005 through 2006, we collected results of sputum smear microscopy for acid-fast bacilli (a marker for infectiousness) and data on visa status, sociodemographics, TB-related care seeking, and latent TB infection (LTBI) diagnosis opportunities. Among 980 persons with pulmonary TB who reported their visa status, 601 (61%) were legal permanent residents, 131 (13.4%) had temporary visas, and 248 (25.3%) were undocumented. Undocumented persons were more likely than permanent residents to have acid-fast bacilli-positive smears at diagnosis (risk ratio = 1.3; 95% confidence interval = 1.2, 1.4). Of those diagnosed 1 year or more after arrival, 57.3% reported LTBI screening opportunities; fewer than 25% actually were. Undocumented persons reported fewer LTBI screening opportunities and were less likely to be tested. Progress toward TB elimination in the United States depends upon expanding opportunities for regular medical care and promotion of LTBI screening and treatment among foreign-born persons.

Acid Fast Bacilli Smear Microscopy Proficiency of 2012 GC Graduating Batch Students in the Field of Medical Laboratory Science in the Three Earliest Universities of Ethiopia

Acid Fast Bacilli Smear Microscopy Proficiency of 2012 GC Graduating Batch Students in the Field of Medical Laboratory Science in the Three Earliest Universities of Ethiopia

A systematic review of hepatic tuberculosis with considerations in human immunodeficiency virus co-infection.

BackgroundMycobacterium tuberculosis (TB) infection of the liver, known as hepatic TB, is an extrapulmonary manifestation of TB. Hepatic TB has become more prevalent, likely as a result of the human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) epidemic. We sought to review case series to characterize the epidemiology, pathophysiology, clinical features, diagnosis, and treatment of hepatic TB and to comment on the impact of HIV co-infection on these characteristics.MethodsWe conducted a systematic literature search in PubMed and ScienceDirect for articles pertaining to hepatic TB with human subjects from 1960 to July 2013.ResultsWe obtained data on 618 hepatic TB patients from 14 case series. The most common reported signs and symptoms were hepatomegaly (median: 80%, range: 10-100%), fever (median: 67%, range: 30–100), respiratory symptoms (median: 66%, range: 32-78%), abdominal pain (median: 59.5%, range: 40-83%), and weight loss (median: 57.5%, range: 20-100%). Common laboratory abnormalities were elevated alkaline phosphatase and gamma-glutamyl transferase. Ultrasound and computerized tomography (CT) were sensitive but non-specific. On liver biopsy, smear microscopy for acid-fast bacilli had a median sensitivity of 25% (range: 0-59%), histology of caseating granulomas had a median sensitivity of 68% (range: 14-100%), and polymerase chain reaction for TB had a median sensitivity of 86% (range: 30-100%). Standard anti-tuberculous chemotherapy for 6 to 12 months achieved positive outcomes for nearly all patients with drug-susceptible TB.ConclusionsClinicians in TB-endemic regions should maintain a high index of suspicion for hepatic TB in patients presenting with hepatomegaly, fever, respiratory symptoms, and elevated liver enzymes. The most sensitive imaging modality is a CT scan, while the most specific diagnostic modality is a liver biopsy with nucleic acid testing of liver tissue samples. Upon diagnosis, 4-drug anti-TB therapy should promptly be initiated. HIV co-infected patients may have more complex cases and should be closely monitored for complications.

Abstract #256: Comparison of Acid Fast Bacilli Smear Microscopy Examination and X-Pert Mtb/Rif in Diagnosis Pulmonary Tuberculosis in type 2 Diabetes

Abstract #256: Comparison of Acid Fast Bacilli Smear Microscopy Examination and X-Pert Mtb/Rif in Diagnosis Pulmonary Tuberculosis in type 2 Diabetes

Comparison of Acid Fast Bacilli Smear Microscopy Examination and Xpert MTB/RIF for the Diagnosis of Pulmonary Tuberculosis in Diabetes Mellitus Patients

People with diabetes mellitus (DM) have 2‐3 times the risk of developing tuberculosis (TB). It has been previously reported (Pablos‐Mendez et al) that only poorly controlled or uncontrolled DM is associated with an increased risk of TB. The main objective of this study was to determine the sensitivity and specificity of Acid Fast Bacilli (AFB) smear and Xpert MTB/RIF for the diagnosis of TB in DM patients. This study was a cross‐sectional descriptive analytic study in patients with DM who underwent treatment at Persahabatan Hospital in 2014. The study was conducted in the Pulmonary and Internal Medicine clinics. Samples were collected from 57 patients with 2 samples excluded due to proven AFB smear but not checked by Xpert MTB/RIF. Among 55 patients, there were 32 males (58.2%) and 23 females (41.8%).The blood sugar ranged between 110‐481 g/dl with a mean of 244.8 ± 98.5 g/dl. HbA1c values were between 5.3‐17.7 with a mean of 9.83 ± 3,00. 41 patients (74.5%) had no previous history of TB; 9 patients (16.4%) were cured of TB; and 5 patients (9.1%) had failure or withdrawal of TB treatment. 28 samples (50.9%) were positive for both AFB smear and Xpert , 1 sample was AFB smear positive and Xpert negative, 8 samples (14.5%) were AFB smear negative but Xpert positive, and 18 samples (32.7%) were negative by both AFB smear and Xpert. Sensitivity and specificity by using both methods were 77.8% and 94.7%, respectively. We conclude that there is no difference in the sensitivity and specificity of AFB smear and Xpert MTB/RIF for TB diagnosis in DM patients.

Prevalence of pulmonary tuberculosis among adults in a north Indian district.

BackgroundRecent population prevalence estimates of pulmonary tuberculosis (PTB) are not available for several areas in India. We conducted a field-based population survey at a north Indian district to estimate point prevalence of bacteriologically positive PTB.MethodsA stratified cluster sampling design was used to conduct the survey in both urban and rural areas within the district. All adults aged more than 15 years, in 18 rural and 12 urban clusters of 3000 subjects each, were interviewed using a symptom card. Two sputum samples were collected from all persons having symptoms suggestive of PTB, or history of antitubercular treatment, for smear microscopy for acid-fast bacilli and mycobacterial culture. Those having at least one sputum specimen positive on microscopy and/or culture were categorized as having PTB. Prevalence was estimated after adjusting for cluster sampling and incomplete data (through individual level analysis with robust standard error).ResultsOf 91,030 eligible adult participants (47,714 men and 43,316 women), 85,770 (94.2%) completed the symptom cards. Of them, 2,898 persons were considered eligible for sputum examination and 2,839 (98.0%) provided at least one sample. Overall, 21 persons had bacteriologically positive PTB, and cluster level prevalence was estimated at 24.5 per 100,000 population (95% CI 12.8–36.2). Individual level analysis with robust standard error yielded a prevalence estimate of 24.1 per 100,000 populations (95% CI 12.8–35.4).ConclusionThe observed prevalence of bacteriologically positive PTB in this district is lower than empiric national estimates, probably as a result of successful implementation of tuberculosis control measures in the area.

Cost-effectiveness analysis of the Xpert MTB/RIF assay for rapid diagnosis of suspected tuberculosis in an intermediate burden area

We examined, from a Hong Kong healthcare providers' perspective, the cost-effectiveness of rapid diagnosis with Xpert in patients hospitalized for suspected active pulmonary tuberculosis (PTB). A decision tree was designed to simulate outcomes of three diagnostic assessment strategies in adult patients hospitalized for suspected active PTB: conventional approach, sputum smear plus Xpert for acid-fast bacilli (AFB) smear-negative, and a single sputum Xpert test. Model inputs were derived from the literature. Outcome measures were direct medical cost, one-year mortality rate, quality-adjusted life-years (QALYs) and incremental cost per QALY (ICER). In the base-case analysis, Xpert was more effective with higher QALYs gained and a lower mortality rate when compared with smear plus Xpert by an ICER of USD99. A conventional diagnostic approach was the least preferred option with the highest cost, lowest QALYs gained and highest mortality rate. Sensitivity analysis showed that Xpert would be the most cost-effective option if the sensitivity of sputum AFB smear microscopy was ≤74%. The probabilities of Xpert, smear plus Xpert and a conventional approach to be cost-effective were 94.5%, 5.5% and 0%, respectively, in 10,000 Monte Carlo simulations. The Xpert sputum test appears to be a highly cost-effective diagnostic strategy for patients with suspected active PTB in an intermediate burden area like Hong Kong.

Comparative analysis of errors in reading sputum smear microscopy by supervisors and peripheral laboratory technicians in southeastern Nigeria

Background: It is important that the quality of microscopy in the peripheral laboratories is monitored in order to provide feedback for improvement of performance of laboratory technicians (LTs). Aim of Study: To compare the errors made in reading sputum smear microscopy for acid-fast bacilli (AFB) by peripheral LTs with those made by secondary level supervisors in the local government areas (LGAs) in the Southeastern states of Nigeria. Materials and Methods: A retrospective study of 15 sputum smear microscopy slides selected systematically from each designated peripheral laboratory and blinded rechecked using the Lot quality assurance (LQA) method between 2006 and 2007 in the southeastern states of Nigeria. Results: The total (major and minor) errors made by both supervisors and peripheral LTs were 189 and 350, respectively. The supervisors made 75 (39.7%) of the total major errors, compared with 114 (60.3%) by peripheral LTs. The supervisors contributed 159 (45.4%) of minor errors, while peripheral LTs contributed 191 (54.6%) of 350. The unpaired Student's t-test values show a statistically significant difference between the mean of high false-positive (HFP), low false-positive (LFP), low false-negative (LF), and quantitative errors, t = 3.794 (P < 0.001); t = 4.146 (P < 0.001); t = 3.059 (P = 0.002) and quantitative errors t = 2.806 (P = 0.005), respectively, between the supervisors and LTs. The exception was in HFN, which was not statistically significant. Conclusion: Although both supervisors and peripheral LTs made both major and minor errors, comparatively supervisors made fewer errors with less variation than the peripheral LTs.

Diagnostic accuracy of a point-of-care urine test for tuberculosis screening among newly-diagnosed hiv-infected adults: a prospective, clinic-based study

BackgroundA rapid diagnostic test for active tuberculosis (TB) at the clinical point-of-care could expedite case detection and accelerate TB treatment initiation. We assessed the diagnostic accuracy of a rapid urine lipoarabinomannan (LAM) test for TB screening among HIV-infected adults in a TB-endemic setting.MethodsWe prospectively enrolled newly-diagnosed HIV-infected adults (≥18 years) at 4 outpatient clinics in Durban from Oct 2011-May 2012, excluding those on TB therapy. A physician evaluated all participants and offered CD4 cell count testing. Trained study nurses collected a sputum sample for acid-fast bacilli smear microscopy (AFB) and mycobacterial culture, and performed urine LAM testing using Determine™ TB LAM in the clinic. The presence of a band regardless of intensity on the urine LAM test was considered positive. We defined as the gold standard for active pulmonary TB a positive sputum culture for Mycobacterium tuberculosis. Diagnostic accuracy of urine LAM was assessed, alone and in combination with smear microscopy, and stratified by CD4 cell count.ResultsAmong 342 newly-diagnosed HIV-infected participants, 190 (56%) were male, mean age was 35.6 years, and median CD4 was 182/mm3. Sixty participants had culture-positive pulmonary TB, resulting in an estimated prevalence of 17.5% (95% CI 13.7-22.0%). Forty-five (13.2%) participants were urine LAM positive. Mean time from urine specimen collection to LAM test result was 40 minutes (95% CI 34–46 minutes). Urine LAM test sensitivity was 28.3% (95% CI 17.5-41.4) overall, and 37.5% (95% CI 21.1-56.3) for those with CD4 count <100/mm3, while specificity was 90.1% (95% CI 86.0-93.3) overall, and 86.9% (95% CI 75.8-94.2) for those with CD4 < 100/mm3. When combined with sputum AFB (either test positive), sensitivity increased to 38.3% (95% CI 26.0-51.8), but specificity decreased to 85.8% (95% CI 81.1-89.7).ConclusionsIn this prospective, clinic-based study with trained nurses, a rapid urine LAM test had low sensitivity for TB screening among newly-diagnosed HIV-infected adults, but improved sensitivity when combined with sputum smear microscopy.

Genital tuberculosis: Comparative study of the diagnostic modalities.

BACKGROUND:Genital tuberculosis (GTB) is one of the major causes for severe tubal disease leading to infertility. Unlike pulmonary tuberculosis (TB), the clinical diagnosis of GTB is difficult because in the majority of cases the disease is either asymptomatic or has varied clinical presentation. Routine laboratory tests are of little value in the diagnosis. The objective of this study was to compare the modalities of polymerase chain reaction (PCR) technique, acid fast bacilli (AFB) culture and AFB staining.MATERIALS AND METHODS:The women visiting in vitro fertility center during December 2012 and May 2013 were included in this study. A total of 227 aseptically collected endometrial tissue samples were processed. AFB staining, AFB culture and PCR were carried out using standard procedures.RESULT:Out of 227 patients suspected of GTB, 133 were found to be positive either by AFB smear microscopy, culture or PCR. Out of 133 samples, two samples (1.5%) were found to be positive by all three methods, i.e. microscopy, culture and PCR, 11 (4.8%) were found to be positive by both PCR and culture, whereas 126 (86%) samples were found to be positive only by PCR. The PCR has failed to detect seven cases that were positive by conventional culture method.CONCLUSION:Our study showed that the conventional methods of diagnosis like microscopy and culture are less sensitive when compared with PCR. PCR also helped in early diagnosis of infection. However simultaneously, false negative results were an important limitation of this method. PCR negative samples were found to be positive by culture methods. Deoxyribose nucleic acid PCR is not reliable for TB due to false positive or negative result. Thus, we suggest both culture and PCR as important diagnostic methods for detection of GTB.

Diagnostic accuracy of Xpert® MTB/RIF on bronchoscopy specimens in patients with suspected pulmonary tuberculosis

To determine the diagnostic accuracy of the Xpert® MTB/RIF assay using samples obtained through bronchoscopy in patients with suspected pulmonary tuberculosis (PTB). We retrospectively reviewed the records of patients with suspected PTB for whom the Xpert MTB/RIF assay was performed on bronchoscopy specimens. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for the diagnosis of active PTB were calculated for acid-fast bacilli (AFB) smear microscopy and the Xpert assay using culture of Mycobacterium tuberculosis from sputum or bronchoscopy specimens as a reference standard. A total of 132 patients were included in the final analysis. Of these, 38 had culture-confirmed PTB. The sensitivity of the Xpert assay using bronchial washing or bronchoalveolar lavage (BAL) fluid for the diagnosis of PTB was 81.6%, and specificity was 100%. The PPV and NPV were 100% and 92.1%, respectively. The sensitivity and specificity of AFB smear microscopy were respectively 13.2% and 98.8%. The Xpert assay on bronchoscopy specimens provided an accurate diagnosis of PTB in patients who had a negative AFB smear or who could not produce sputum.

Screening patients with Diabetes Mellitus for Tuberculosis in China

There is a high burden of both diabetes (DM) and tuberculosis (TB) in China, and as DM increases the risk of TB and adversely affects TB treatment outcomes, there is a need for bidirectional screening of the two diseases. How this is best performed is not well determined. In this pilot project in China, we aimed to assess the feasibility and results of screening DM patients for TB within the routine healthcare setting of five DM clinics. Agreement on how to screen, monitor and record was reached in May 2011 at a national stakeholders meeting, and training was carried out for staff in the five clinics in July 2011. Implementation started in September 2011, and we report on 7 months of activities up to 31 March 2012. DM patients were screened for TB at each clinic attendance using a symptom-based enquiry, and those positive to any symptom were referred for TB investigations. In the three quarters, 72% of 3174 patients, 79% of 7196 patients and 68% of 4972 patients were recorded as having been screened for TB, resulting in 7 patients found who were already known to have TB, 92 with a positive TB symptom screen and 48 of these newly diagnosed with TB as a result of referral and investigation. All patients except one were started on anti-TB treatment. TB case notification rates in screened DM patients were several times higher than those of the general population, were highest for the five sites combined in the final quarter (774/100 000) and were highest in one of the five clinics in the final quarter (804/100 000) where there was intensive in-house training, special assignment of staff for screening and colocation of services. This pilot project shows that it is feasible to carry out screening of DM patients for TB resulting in high detection rates of TB. This has major public health and patient-related implications.

Variability of infectious aerosols produced during coughing by patients with pulmonary tuberculosis.

Mycobacterium tuberculosis is transmitted by infectious aerosols, but assessing infectiousness currently relies on sputum microscopy that does not accurately predict the variability in transmission. To evaluate the feasibility of collecting cough aerosols and the risk factors for infectious aerosol production from patients with pulmonary tuberculosis (TB) in a resource-limited setting. We enrolled subjects with suspected TB in Kampala, Uganda and collected clinical, radiographic, and microbiological data in addition to cough aerosol cultures. A subset of 38 subjects was studied on 2 or 3 consecutive days to assess reproducibility. M. tuberculosis was cultured from cough aerosols of 28 of 101 (27.7%; 95% confidence interval [CI], 19.9-37.1%) subjects with culture-confirmed TB, with a median 16 aerosol cfu (range, 1-701) in 10 minutes of coughing. Nearly all (96.4%) cultivable particles were 0.65 to 4.7 μm in size. Positive aerosol cultures were associated with higher Karnofsky performance scores (P = 0.016), higher sputum acid-fast bacilli smear microscopy grades (P = 0.007), lower days to positive in liquid culture (P = 0.004), stronger cough (P = 0.016), and fewer days on TB treatment (P = 0.047). In multivariable analyses, cough aerosol cultures were associated with a salivary/mucosalivary (compared with purulent/mucopurulent) appearance of sputum (odds ratio, 4.42; 95% CI, 1.23-21.43) and low days to positive (per 1-d decrease; odds ratio, 1.17; 95% CI, 1.07-1.33). The within-test (kappa, 0.81; 95% CI, 0.68-0.94) and interday test (kappa, 0.62; 95% CI, 0.43-0.82) reproducibility were high. A minority of patients with TB (28%) produced culturable cough aerosols. Collection of cough aerosol cultures is feasible and reproducible in a resource-limited setting.

Effectiveness of the BDProbeTec ET system for detection of Mycobacterium tuberculosis complex in sputum and bronchoalveolar lavage specimens

OBJECTIVE: The diagnostic efficacy of the BDProbeTEC ET Mycobacterium tuberculosis (MTB) complex direct detection assay (DTB) performed on bronchoalveolar lavage (BAL) specimens and sputum smears was compared with acid-fast bacilli (AFB) smear microscopy. METHOD: AFB smear microscopy, DTB and culture results of 286 patients with pulmonary tuberculosis were retrospectively reviewed. A total of 120 patients provided expectorated sputum samples, and 166 patients provided BAL specimens. Culture results and clinical diagnosis were used as gold standards. RESULTS: The sensitivity and specificity of the DTB assay in detecting MTB in sputum specimens was significantly higher compared to AFB smear microscopy (83.7% and 82.4%, vs. 75.6%, and 41.2%, respectively). The sensitivity and specificity of the DTB assay in detecting MTB in sputum samples was 77.2% and 100% compared to clinical diagnosis, while AFB smear had a sensitivity and specificity of 70.3% and 26.3%, respectively. Compared to culture, DTB had a sensitivity and specificity of 82.8% and 93.2%, respectively, in detecting MTB from BAL specimens; AFB smear had a sensitivity and specificity of 41.9% and 87.7%, respectively. Compared to clinical diagnosis, DTB had a sensitivity and specificity of 67.2% and 100%, respectively, in detecting MTB from BAL specimens; AFB smear had a sensitivity and specificity of 34.8% and 79.5%, respectively. CONCLUSIONS: The superior performance of the DTB assay relative to AFB smear microscopy makes it a valuable tool to enable early diagnosis of MTB, thereby improving patient care and reducing transmission.

Effectiveness of the BDProbeTec ET system for detection of Mycobacterium tuberculosis complex in sputum and bronchoalveolar lavage specimens

ObjectiveThe diagnostic efficacy of the BDProbeTEC ET Mycobacterium tuberculosis (MTB) complex direct detection assay (DTB) performed on bronchoalveolar lavage (BAL) specimens and sputum smears was compared with acid-fast bacilli (AFB) smear microscopy. MethodAFB smear microscopy, DTB and culture results of 286 patients with pulmonary tuberculosis were retrospectively reviewed. A total of 120 patients provided expectorated sputum samples, and 166 patients provided BAL specimens. Culture results and clinical diagnosis were used as gold standards. ResultsThe sensitivity and specificity of the DTB assay in detecting MTB in sputum specimens was significantly higher compared to AFB smear microscopy (83.7% and 82.4%, vs. 75.6%, and 41.2%, respectively). The sensitivity and specificity of the DTB assay in detecting MTB in sputum samples was 77.2% and 100% compared to clinical diagnosis, while AFB smear had a sensitivity and specificity of 70.3% and 26.3%, respectively. Compared to culture, DTB had a sensitivity and specificity of 82.8% and 93.2%, respectively, in detecting MTB from BAL specimens; AFB smear had a sensitivity and specificity of 41.9% and 87.7%, respectively. Compared to clinical diagnosis, DTB had a sensitivity and specificity of 67.2% and 100%, respectively, in detecting MTB from BAL specimens; AFB smear had a sensitivity and specificity of 34.8% and 79.5%, respectively. ConclusionsThe superior performance of the DTB assay relative to AFB smear microscopy makes it a valuable tool to enable early diagnosis of MTB, thereby improving patient care and reducing transmission.

Symptom screen: diagnostic usefulness in detecting pulmonary tuberculosis in HIV-infected pregnant women in Kenya

To determine the diagnostic usefulness of tuberculosis (TB) symptom screening to detect active pulmonary TB among human immunodeficiency virus (HIV) infected pregnant women in two PMTCT (prevention of mother-to-child transmission) clinics in western Kenya that are supported by the United States Agency for International Development-Academic Model Providing Access to Healthcare partnership. Cross-sectional study. Participants were interviewed for TB symptoms with a standardized questionnaire (cough >2 weeks, fever, night sweats, weight loss or failure to gain weight). Those with cough submitted sputum specimens for smear microscopy for acid-fast bacilli and mycobacterial culture. Women at >14 weeks gestation underwent shielded chest radiography (CXR). Of 187 HIV-infected women, 38 (20%) were symptom screen-positive. Of these, 21 had a cough for >2 weeks, but all had negative sputum smears and mycobacterial cultures. CXRs were performed in 26 symptomatic women: three were suggestive of TB (1 miliary, 1 infiltrates and 1 cavitary). Of 149 women with a negative symptom screen, 100 had a CXR and seven had a CXR suggestive of TB (1 cavitary, 2 miliary and 4 infiltrates). This study did not support the utility of isolated symptom screening in identification of TB disease in our PMTCT setting. CXR was useful in identification of TB suspects in both symptomatic and asymptomatic women.

Comparison of Xpert MTB/RIF with Other Nucleic Acid Technologies for Diagnosing Pulmonary Tuberculosis in a High HIV Prevalence Setting: A Prospective Study

The Xpert MTB/RIF (Cepheid) non-laboratory-based molecular assay has potential to improve the diagnosis of tuberculosis (TB), especially in HIV-infected populations, through increased sensitivity, reduced turnaround time (2 h), and immediate identification of rifampicin (RIF) resistance. In a prospective clinical validation study we compared the performance of Xpert MTB/RIF, MTBDRplus (Hain Lifescience), LightCycler Mycobacterium Detection (LCTB) (Roche), with acid fast bacilli (AFB) smear microscopy and liquid culture on a single sputum specimen. Consecutive adults with suspected TB attending a primary health care clinic in Johannesburg, South Africa, were prospectively enrolled and evaluated for TB according to the guidelines of the National TB Control Programme, including assessment for smear-negative TB by chest X-ray, clinical evaluation, and HIV testing. A single sputum sample underwent routine decontamination, AFB smear microscopy, liquid culture, and phenotypic drug susceptibility testing. Residual sample was batched for molecular testing. For the 311 participants, the HIV prevalence was 70% (n = 215), with 120 (38.5%) culture-positive TB cases. Compared to liquid culture, the sensitivities of all the test methodologies, determined with a limited and potentially underpowered sample size (n = 177), were 59% (47%-71%) for smear microscopy, 76% (64%-85%) for MTBDRplus, 76% (64%-85%) for LCTB, and 86% (76%-93%) for Xpert MTB/RIF, with specificities all >97%. Among HIV+ individuals, the sensitivity of the Xpert MTB/RIF test was 84% (69%-93%), while the other molecular tests had sensitivities reduced by 6%. TB detection among smear-negative, culture-positive samples was 28% (5/18) for MTBDRplus, 22% (4/18) for LCTB, and 61% (11/18) for Xpert MTB/RIF. A few (n = 5) RIF-resistant cases were detected using the phenotypic drug susceptibility testing methodology. Xpert MTB/RIF detected four of these five cases (fifth case not tested) and two additional phenotypically sensitive cases. The Xpert MTB/RIF test has superior performance for rapid diagnosis of Mycobacterium tuberculosis over existing AFB smear microscopy and other molecular methodologies in an HIV- and TB-endemic region. Its place in the clinical diagnostic algorithm in national health programs needs exploration. Please see later in the article for the Editors' Summary.

Fine needle aspiration cytology and the choice of fixatives in the diagnosis of tuberculous adenitis at Muhimbili National Hospital, Dar-es-Salaam, Tanzania

Tuberculosis (TB) is a global public health problem. Despite recent success in improving TB cure rates, diagnosis and case detection remains a major obstacle to its control. In this study the usefulness of four fixatives in improving Acid Fast Bacilli (AFB) microscopy diagnosis of TB was assessed. The study was conducted at Muhimbili National Hospital(MNH) in Dar es Salaam, Tanzania. A total of 560 cases of peripheral lymphadenopathies had fine needle aspiration cytology (FNAC) done. Out of these cases, 110 (19.6%) were diagnosed by ZN stain to be TB lymphadenitis. Different types of fixatives in diagnosis of TB were compared. Each specimen was smeared and fixed on to four glass slides using four fixatives (95% ethyl alcohol, Acetone, Carnoy’s fluid and 10% neutral buffered formalin), and one slide fixed using air dried method. Subsequently, Zeelh-Neelsen (ZN) stained slides were examined under a microscope for AFB. Of the 101 cases, 53 were TB adenitis, as diagnosed by AFB smear microscopy on ZN stained slides, and 48 were adenitis due to other causes. The diagnostic yield of AFB was highest when using 95% ethyl alcohol which was observed to be 30.2% (16/53) when AFB was 1+, 58.5% (31/53) when AFB was 2+ and 11.3% (6/53) when AFB was 3+, and making a total yield of 100% (53/53). Air dried smears also gave a relatively high yield with total yield of 94.3% (50/53). When 95% ethyl alcohol was used as a gold standard fixative, air dried slides had highest sensitivity (94.3%) and all fixatives had high specificity. The study has demonstrated that 95% ethyl alcohol is an excellent fixative. It is therefore recommended that 95% ethyl alcohol be used to form part of the routine fixation of FNAC smears.

Cost-effectiveness analysis of PCR for the rapid diagnosis of pulmonary tuberculosis

BackgroundTuberculosis is one of the most prominent health problems in the world, causing 1.75 million deaths each year. Rapid clinical diagnosis is important in patients who have co-morbidities such as Human Immunodeficiency Virus (HIV) infection. Direct microscopy has low sensitivity and culture takes 3 to 6 weeks [1-3]. Therefore, new tools for TB diagnosis are necessary, especially in health settings with a high prevalence of HIV/TB co-infection.MethodsIn a public reference TB/HIV hospital in Brazil, we compared the cost-effectiveness of diagnostic strategies for diagnosis of pulmonary TB: Acid fast bacilli smear microscopy by Ziehl-Neelsen staining (AFB smear) plus culture and AFB smear plus colorimetric test (PCR dot-blot).From May 2003 to May 2004, sputum was collected consecutively from PTB suspects attending the Parthenon Reference Hospital. Sputum samples were examined by AFB smear, culture, and PCR dot-blot. The gold standard was a positive culture combined with the definition of clinical PTB. Cost analysis included health services and patient costs.ResultsThe AFB smear plus PCR dot-blot require the lowest laboratory investment for equipment (US$ 20,000). The total screening costs are 3.8 times for AFB smear plus culture versus for AFB smear plus PCR dot blot costs (US$ 5,635,760 versus US$ 1,498, 660). Costs per correctly diagnosed case were US$ 50,773 and US$ 13,749 for AFB smear plus culture and AFB smear plus PCR dot-blot, respectively. AFB smear plus PCR dot-blot was more cost-effective than AFB smear plus culture, when the cost of treating all correctly diagnosed cases was considered. The cost of returning patients, which are not treated due to a negative result, to the health service, was higher in AFB smear plus culture than for AFB smear plus PCR dot-blot, US$ 374,778,045 and US$ 110,849,055, respectively.ConclusionAFB smear associated with PCR dot-blot associated has the potential to be a cost-effective tool in the fight against PTB for patients attended in the TB/HIV reference hospital.

Metodologia para caracterização de proficiência em leitura de resultados baciloscópicos para o diagnóstico da tuberculose

To propose a methodology for characterizing proficiency in sputum smear microscopy for acid-fast bacilli (AFB) in the diagnosis of tuberculosis and to determine the number of microscopies necessary to establish this proficiency, as well as the quality of the transcription of results, the causes of the discrepancies in the readings (rater or microscope used), and the criterion for classification of microscopy results that poses the most difficulty in characterizing proficiency. Four hundred sputum smear microscopies for the diagnosis of tuberculosis were analyzed through double-blind readings by six professionals who usually read/supervise microscopies performed in public health care facilities. The sample was stratified to obtain, at least, a reliability of 90% in the double-blind readings, an alpha error of 5%, and a precision of 3%. The results were analyzed using observed reliability and the kappa index. Thirteen errors (0.27%) were found in the transcription of results. Reliability increased when the three distinct categories of positive results (AFB+, AFB++, and AFB+++) were grouped or when inconclusive results were excluded from the analysis. The quantification of the bacterial load was the classification criterion that posed the most difficulty in establishing proficiency. Using higher quality microscopes increased reliability. Reliability values stabilized only from the reading of 75 microscopies onward. Double-blind sputum smear microscopy readings using a panel containing 75 slides (36 negative, 4 inconclusive, and 35 positive) proved to be appropriate for characterizing proficiency in sputum smear microscopy for the diagnosis of tuberculosis when such proficiency is intended to reproduce laboratory routine.