The tuberculosis control program is based on a felt need–oriented basis. The diagnosis is mainly microbiological. However, sputum smear-negative Acid Fast Bacilli (AFB) cases with suspected radiological findings can be problematic in diagnosis.
To confirm the diagnosis of tuberculosis early, in smear-negative AFB cases by using a Fiberoptic Bronchoscope.
Materials and Methods:
We embarked on Fiberoptic Bronchoscopy (FOB) and Spot Scopy smear Microscopy (SSM) for 533 suspected Pulmonary Tuberculosis (PT) cases (sputum smear negative and radiologically suggestive) from February 2007 to May 2010. FOB was performed using a special device, a Trans Oro Pharyngeal Spacer (TOPS), as a conduit.
The yield for positivity for AFB was 341 (64%) out of 533 cases.
Conclusion and Recommendation:
The specimens collected by using the fiberoptic bronchoscope confirmed the disease in the smear-negative cases. Hence, FOB was recommended in smear-negative cases, to avoid delay in the treatment of tuberculosis.
Fiberoptic bronchoscopy; pulmonary tuberculosis; spot scopy smear microscopy; trans oro pharyngeal spacer
The World Health Organization (WHO) recommends collection of two sputum samples for tuberculosis (TB) diagnosis, with at least one being an early morning (EM) using smear microscopy. It remains unclear whether this is necessary even when sputum culture is employed. Here, we determined the diagnostic yield from spot and the incremental yield from the EM sputum sample cultures among TB-suspected adolescents from rural Uganda.
Sputum samples (both spot and early-morning) from 1862 adolescents were cultured by the Lowenstein-Jensen (LJ) and Mycobacterium Growth Indicator Tube (MGIT) methods. For spot samples, the diagnostic yields for TB were 19.0% and 57.1% with LJ and MGIT, respectively, whereas the incremental yields (not totals) of the early-morning sample were 9.5% and 42.9% (P < 0.001) with LJ and MGIT, respectively. Among TB-suspected adolescents in rural Uganda, the EM sputum culture has a high incremental diagnostic yield. Therefore, EM sputum in addition to spot sample culture is necessary for improved TB case detection.
Childhood pulmonary TB (PTB) is under diagnosed, in part due to difficulties in obtaining microbiological confirmation. However, given the poor specificity of clinical diagnosis, microbiological confirmation and drug susceptibility testing is important in guiding appropriate therapy especially in the context of drug resistant TB. Confirmation is often possible, even in infants and young children, if adequate specimens are collected. Culture yield varies with the severity of illness, specimen type and culture method. Induced sputum is recognised as a safe procedure with a high diagnostic yield. Advances include optimised protocols for smear microscopy and modified culture techniques, such as the Microscopic Observation Drug Susceptibility Assay. Detection of Mycobacterium tuberculosis nucleic acid in respiratory specimens has high specificity but relatively poor sensitivity, particularly for smear negative disease. The recent development of an integrated specimen processing and real-time PCR testing platform for M. tuberculosis and rifampicin resistance is an important advance that requires evaluation in childhood TB.
induced sputum; culture; nucleic acid amplification; pulmonary tuberculosis; child
In 126 patients with anogenital lesions, in which herpes simplex virus (HSV) infection was suspected or included in the differential diagnosis, the results of cytodiagnosis of herpetic infection (Tzanck smear) were compared with virus culture. Cervical lesions were excluded from this study. HSV infection was proved by culture in 78 patients and was absent or non-active in 41 patients. Excluded from this study were seven patients who did not yield the virus on culture but had positive Tzanck smear results from three investigators. The characteristic cytopathic effect of herpetic infection was found in 78 patients who yielded HSV on culture. Tzanck smear sensitivity for skin lesions was 79% and for mucous membrane lesions was 81% in men and 52% in women. Tzanck smear specificity for the 41 patients without herpetic infection proved by virus culture was 93%. Differences in sensitivity and specificity between the results found by three investigators (double blind screening) were not significant. The Tzanck smear is reliable, inexpensive, and easy and quick to perform; it is suitable for office diagnosis because it does not require a specialised laboratory.
Techniques to improve the sensitivity of smear microscopy would facilitate early tuberculosis (TB) diagnosis and disease control, especially in low-income countries where the positive predictive value is high. C18-carboxypropylbetaine (CB-18) is a zwitterionic detergent that helps to compensate for the innate buoyancy of mycobacteria, potentially enhancing recovery by centrifugation. Previous data suggest that CB-18 may increase the sensitivity of smear, culture, and molecular amplification diagnostic testing. The goal of the present study was to evaluate if the sensitivity of the smear technique using light microscopy could be improved by treating respiratory samples with CB-18. In the first phase, respiratory specimens were collected consecutively from patients with suspected pulmonary tuberculosis in a tertiary-care hospital in Rio de Janeiro, Brazil (236 specimens were analyzed). After protocol modifications, another 120 respiratory specimens were evaluated. The standard technique was N-acetyl-l-cysteine with sodium hydroxide (NALC-NaOH) treatment, smear concentration with centrifugation, and Ziehl-Neelsen staining. Culture on Löwenstein-Jensen slants was performed on all specimens for use as the “gold standard.” No specimens from patients undergoing active TB treatment were included. The initial protocol for CB-18 processing resulted in a sensitivity of 59.6% and specificity of 96.8% compared to standard processing with a sensitivity of 66.0% and specificity of 96.8%. Using the modified protocol, the sensitivity of CB-18 increased to 71.4% with a specificity of 97.0% versus standard processing with a sensitivity of 61.9% and a specificity of 99.0%. The diagnostic yield of acid-fast bacillus smear with CB-18 in the absence of fluorescence microscopy and PCR compared to standard processing with NALC-NaOH was not significantly different, although the power to detect a difference by the modified assay was low.
The study was conducted at a high TB-HIV burden primary health community clinic in Cape Town, South Africa. We describe the management of children under five years of age in household contact with a smear and/or culture-positive adult TB case.
This study was a record review of routinely-collected programme data.
A total of 1094 adult TB case folders were reviewed. From all identified contacts, 149 children should have received IPT based on local guidelines; in only 2/149 IPT was initiated. Management of child contacts of sputum smear and/or culture-positive compared to sputum-negative TB patients were similar.
IPT delivery to children remains an operational challenge, especially in high TB-HIV burden communities. A tool to improve IPT management and targeting sputum smear and/or culture-positive TB child contacts may overcome some of these challenges and should be developed and piloted in such settings.
Direct sputum smear microscopy for tuberculosis (TB) lacks sensitivity for the detection of acid fast bacilli. Sputum pretreatment procedures may enhance sensitivity. We did a pilot study to compare the diagnostic accuracy and incremental yield of two short-duration (<1 hour) sputum pretreatment procedures to optimize direct smears among patients with suspected TB at a referral hospital in India.
Blinded laboratory comparison of bleach and universal sediment processing (USP) pretreated centrifuged auramine smears to direct Ziehl-Neelsen (ZN) and direct auramine smears and to solid (Loweinstein-Jensen (LJ)) and liquid (BACTEC 460) culture. 178 pulmonary and extrapulmonary TB suspects were prospectively recruited during a one year period. Thirty six (20.2%) were positive by either solid or liquid culture. Direct ZN smear detected 22 of 36 cases and direct auramine smears detected 26 of 36 cases. Bleach and USP centrifugation detected 24 cases each, providing no incremental yield beyond direct smears. When compared to combined culture, pretreated smears were not more sensitive than direct smears (66.6% vs 61.1 (ZN) or 72.2 (auramine)), and were not more specific (92.3% vs 93.0 (ZN) or 97.2 (auramine).
Short duration sputum pretreatment with bleach and USP centrifugation did not increase yield as compared to direct sputum smears. Further work is needed to confirm this in a larger study and also determine if longer duration pre-treatment might be effective in optimizing smear microscopy for TB.
In 2007 WHO issued a guideline to improve the diagnosis of smear-negative and extrapulmonary tuberculosis (EPTB) in HIV-positive patients. This guideline relies heavily on the acceptance of HIV-testing and availability of chest X-rays.
Methods and Findings
Cohort study of TB suspects in four tuberculosis (TB) clinics in Phnom Penh, Cambodia. We assessed the operational performance of the guideline, the incremental yield of investigations, and the diagnostic accuracy for smear-negative tuberculosis in HIV-positive patients using culture positivity as reference standard. 1,147 (68.9%) of 1,665 TB suspects presented with unknown HIV status, 1,124 (98.0%) agreed to be tested, 79 (7.0%) were HIV-positive. Compliance with the guideline for chest X-rays and sputum culture requests was 97.1% and 98.3% respectively. Only 35 of 79 HIV-positive patients (44.3%) with a chest X-ray suggestive of TB started TB treatment within 10 days. 105 of 442 HIV-positive TB suspects started TB treatment (56.2% smear-negative pulmonary TB (PTB), 28.6% smear-positive PTB, 15.2% EPTB). The median time to TB treatment initiation was 5 days (IQR: 2–13 days), ranging from 2 days (IQR: 1–11.5 days) for EPTB, over 2.5 days (IQR: 1–4 days) for smear-positive PTB to 9 days (IQR: 3–17 days) for smear-negative PTB. Among the 34 smear-negative TB patients with a confirmed diagnosis, the incremental yield of chest X-ray, clinical suspicion or abdominal ultrasound, and culture was 41.2%, 17.6% and 41.2% respectively. The sensitivity and specificity of the algorithm to diagnose smear-negative TB in HIV-positive TB suspects was 58.8% (95%CI: 42.2%–73.6%) and 79.4% (95%CI: 74.8%–82.4%) respectively.
Pending point-of-care rapid diagnostic tests for TB disease, diagnostic algorithms are needed. The diagnostic accuracy of the 2007 WHO guideline to diagnose smear-negative TB is acceptable. There is, however, reluctance to comply with the guideline in terms of immediate treatment initiation.
Sputum culture is the gold standard for diagnosis of pulmonary tuberculosis (PTB). Although mostly used for research, culture is recommended by the World Health Organization for TB diagnosis among HIV infected smear negative PTB suspects. Even then, the number of sputum samples required remains unspecified. Here, we determined the Incremental Yield (IY) and number of samples required to diagnose an additional PTB case upon second and third serial sputum culture.
This was a cross sectional study done between January and March 2011. Serial sputum samples were provided by participants within two days and cultured using Lowenstein Jensen (LJ) and Mycobacteria Growth Indicator Tube (MGIT) methods. A PTB case was defined as a positive culture on either one or both methods. The IY from the second and third serial cultures was determined and the reciprocal of the product of the fractions of IY provided the number of samples required for an additional PTB case. Of the 170 smear negative PTB suspects, 62 (36.5%) met the case definition. The IY of the second sample culture was 12.7%, 23.6% and 12.6% and for the third sample culture was 6.8%, 7.5% and 7.3% with LJ, MGIT and LJ or MGIT, respectively. The number of samples required for an additional PTB case and 95% CI upon the second sample culture were 29.9 (16.6, 156.5), 11.3 (7.6, 21.9) and 20.8 (12.5, 62.7); while for the third sample culture were 55.6 (26.4, 500.4), 35.7 (19.0, 313.8) and 36.1 (19.1, 330.9) by LJ, MGIT and LJ or MGIT respectively.
Among HIV infected smear negative PTB suspects in Kampala, 93% of PTB cases are diagnosed upon the second serial sputum culture. The number of cultures needed to diagnose an additional PTB case, ranges from 11–30 and 35–56 by the second and third sputum samples, respectively.
In Africa, tuberculous meningitis (TBM) is an important opportunistic infection in HIV-positive patients. Current diagnostic tools for TBM perform sub-optimally. In particular, the rapid diagnosis of TBM is challenging because smear microscopy has a low yield and PCR is not widely available in resource-poor settings.
We evaluated the performance outcome of a novel standardized lipoarabinomannan (LAM) antigen-detection assay, using archived cerebrospinal fluid samples, in 50 African TBM suspects of whom 68% were HIV-positive.
Of the 50 participants 14, 23 and 13 patients had definite, probable and non-TBM, respectively. In the non-TB group there were 5 HIV positive patients who were lost to follow-up and in whom concomitant infection with Mycobacterium tuberculosis could not be definitively excluded. The test sensitivities and specificities were as follows: LAM assay 64% and 69% (cut-point 0.22), smear microscopy 0% and 100% and PCR 93% and 77%, respectively.
In this preliminary proof-of-concept study, a rapid diagnosis of TBM could be achieved using LAM antigen detection. Although specificity was sub-optimal, the estimates provided here may be unreliable because of a classification bias inherent in the study design where it was not possible to exclude TBM in the presumed non-TBM cases owing to a lack of clinical follow-up. As PCR is largely unavailable, the LAM assay may well prove to be a useful adjunct for the rapid diagnosis of TBM in high HIV-incidence settings. These preliminary results justify further enquiry and prospective studies are now required to definitively establish the place of this technology for the diagnosis of TBM.
Existing tuberculosis control strategies in Vietnam are based on symptomatic patients attending health services for investigation. This approach has not resulted in substantial reductions in the prevalence of tuberculosis disease, despite the National Tuberculosis Program achieving high treatment completion rates. Alternative approaches are being considered.
To determine the feasibility and yield of contact investigation in households of patients with smear positive pulmonary tuberculosis among household members of tuberculosis patients in Hanoi, Vietnam.
Household contacts of patients with smear positive pulmonary tuberculosis were recruited at four urban and rural District Tuberculosis Units in Hanoi. Clinical and radiological screening was conducted at baseline, six months and 12 months. Sputum microscopy and culture was performed in contacts suspected of having tuberculosis. MIRU-VNTR molecular testing was used to compare the strains of patients and their contacts with disease.
Among 545 household contacts of 212 patients, four were diagnosed with tuberculosis at baseline (prevalence 734 cases per 100,000 persons, 95% CI 17–1451) and one was diagnosed with tuberculosis during the subsequent 12 months after initial screening (incidence 180 cases per 100,000 person-years, 95% CI 44–131). Two of these cases were culture positive for M. tuberculosis and both had identical or near-identical MIRU-VNTR strain types.
Household contacts of patients with potentially infectious forms of tuberculosis have a high prevalence of disease. Household contact investigation is feasible in Vietnam. Further research is required to investigate its effectiveness.
This study was performed to assess the efficiency of polymerase chain reaction (PCR) directly from sputum for the diagnosis of pulmonary tuberculosis by comparison between HIV-positive and HIV-negative individuals. Sputum samples were collected from hospitalized patients admitted with a clinical diagnosis of pulmonary tuberculosis, and subjected to smear microscopy, culture on LJ medium and detection of M. tuberculosis by PCR. Sensitivity, specificity, and predictive values (positive and negative) were calculated using smear and/or culture at day 42 as the gold standard, by comparing the yield in HIV-positive and HIV-negative individuals. Regardless of serostatus, the technique’s yield had 62% sensitivity, 70% specificity, 79% positive predictive value, 50% negative predictive value, and 65% accuracy. HIV-negative had 64% sensitivity, 74% specificity, 75% positive predictive value, 63% negative predictive value, and 68% accuracy. HIV-positive had 59% sensitivity, 33% specificity, 87% positive predictive value, 10% negative predictive value, and 56% accuracy. The PCR showed a higher yield in HIV-negative individuals compared to HIV-positive individuals.
Tuberculosis; HIV; PCR; Sputum
Interferon γ release assays (IGRAs) are increasingly used for tuberculosis (TB) infection, but their incremental value beyond patient demographics, clinical signs and conventional tests for active disease has not been evaluated in children.
The incremental value of T-SPOT.TB was assessed in 491 smear-negative children from two hospitals in Cape Town, South Africa. Bayesian model averaging was used to select the optimal set of patient demographics and clinical signs for predicting culture-confirmed TB. The added value of T-SPOT.TB over and above patient characteristics and conventional tests was measured using statistics such as the difference in the area under the receiver operating characteristic curve (AUC), the net reclassification improvement (NRI) and the integrated discrimination improvement (IDI).
Cough longer than 2 weeks, fever longer than 2 weeks, night sweats, malaise, history of household contact and HIV status were the most important predictors of culture-confirmed TB. Binary T-SPOT.TB results did not have incremental value when added to the baseline model with clinical predictors, chest radiography and the tuberculin skin test. The AUC difference was 3% (95% CI 0% to 7%). Using risk cut-offs of <10%, 10–30% and >30%, the NRI was 7% (95% CI −8% to 31%) but the CI included the null value. The IDI was 3% (95% CI 0% to 11%), meaning that the average predicted probability across all possible cut-offs improved marginally by 3%.
In a high-burden setting, the T-SPOT.TB did not have added value beyond clinical data and conventional tests for diagnosis of TB disease in smear-negative children.
Clinical Epidemiology; Tuberculosis
“TBDx” is an innovative smear microscopy system that automatically loads slides onto a microscope, focuses and digitally captures images and then classifies smears as positive or negative using computerised algorithms.
To determine the diagnostic accuracy of TBDx, using culture as the gold standard, and compare this to a microscopist's diagnostic performance.
This study is nested within a cross-sectional study of tuberculosis suspects from South African gold mines. All tuberculosis suspects had one sputum sample collected, which was decontaminated prior to smear microscopy, liquid culture and organism identification. All slides were auramine-stained and then read by both a research microscopist and by TBDx using fluorescence microscopes, classifying slides based on the WHO classification standard of 100 fields of view (FoV) at 400× magnification.
Of 981 specimens, 269 were culture positive for Mycobacterium tuberculosis (27.4%). TBDx had higher sensitivity than the microscopist (75.8% versus 52.8%, respectively), but markedly lower specificity (43.5% versus 98.6%, respectively). TBDx classified 520/981 smears (53.0%) as scanty positive. Hence, a proposed hybrid software/human approach that combined TBDx examination of all smears with microscopist re-examination of TBDx scanty smears was explored by replacing the “positive” result of slides with 1–9 AFB detected on TBDx with the microscopist's original reading. Compared to using the microscopist's original results for all 981 slides, this hybrid approach resulted in equivalent specificity, a slight reduction in sensitivity from 52.8% to 49.4% (difference of 3.3%; 95% confidence interval: 0.2%, 6.5%), and a reduction in the number of slides to be read by the microscopist by 47.0%.
Compared to a research microscopist, the hybrid software/human approach had similar specificity and positive predictive value, but sensitivity requires further improvement. Automated microscopy has the potential to substantially reduce the number of slides read by microscopists.
Culture of Mycobacterium tuberculosis currently
represents the closest “gold standard” for
diagnosis of tuberculosis (TB), but operational data are scant on the
impact and cost-effectiveness of TB culture for human immunodeficiency
(HIV-) infected individuals in resource-limited settings.
We recorded costs, laboratory results, and dates of initiating TB therapy
in a centralized TB culture program for HIV-infected patients in Rio de
Janeiro, Brazil, constructing a decision-analysis model to estimate the
incremental cost-effectiveness of TB culture from the perspective of a
public-sector TB control program. Of 217 TB suspects presenting between
January 2006 and March 2008, 33 (15%) had culture-confirmed
active tuberculosis; 23 (70%) were smear-negative. Among
smear-negative, culture-positive patients, 6 (26%) began TB
therapy before culture results were available, 11 (48%)
began TB therapy after culture result availability, and 6
(26%) did not begin TB therapy within 180 days of
presentation. The cost per negative culture was US$17.52
(solid media)–$23.50 (liquid media). Per 1,000
TB suspects and compared with smear alone, TB culture with solid media
would avert an estimated eight TB deaths (95% simulation
interval [SI]: 4, 15) and 37 disability-adjusted
life years (DALYs) (95% SI: 13, 76), at a cost of
$36 (95% SI: $25, $50)
per TB suspect or $962 (95% SI:
$469, $2642) per DALY averted. Replacing solid
media with automated liquid culture would avert one further death
(95% SI: −1, 4) and eight DALYs (95%
SI: −4, 23) at $2751 per DALY (95%
SI: $680, dominated). The cost-effectiveness of TB culture
was more sensitive to characteristics of the existing TB diagnostic
system than to the accuracy or cost of TB culture.
TB culture is potentially effective and cost-effective for HIV-positive
patients in resource-constrained settings. Reliable transmission of
culture results to patients and integration with existing systems are
The genetically detoxified Bordetella pertussis adenylate cyclase is a promising delivery system for immunodominant tuberculosis antigens in gamma interferon release assays. This system has not been evaluated in human immunodeficiency virus (HIV)-infected persons in high tuberculosis prevalence areas. A whole-blood gamma interferon release assay with Mycobacterium tuberculosis antigens (early-secreted antigenic target 6, culture filtrate protein 10, alpha-crystallin 2, and TB10.3) delivered by adenylate cyclase in addition to native tuberculosis antigens (without adenylate cyclase delivery) was evaluated in 119 adults in Khayelitsha Township, Cape Town, South Africa. Results were compared to tuberculin skin test results of 41 HIV-positive and 42 HIV-negative asymptomatic persons, in addition to 36 HIV-positive persons with recently diagnosed smear- or culture-positive pulmonary tuberculosis. Delivery of tuberculosis antigens by adenylate cyclase decreased by 10-fold the amount of antigen required to restimulate T cells. Furthermore, the responses of HIV-positive persons with a low response to native tuberculosis antigens were enhanced when these antigens were delivered by adenylate cyclase. When gamma interferon responses to the tuberculosis antigens (with or without delivery by adenylate cyclase) were combined, a significantly higher number of patients were scored positive than by tuberculin skin testing. Ex vivo responses to tuberculosis antigens delivered by adenylate cyclase are maintained in the context of HIV infection. Our findings suggest that the majority of those in this population are infected with tuberculosis, which is of significant public health importance.
Smear-negative tuberculosis occurs more frequently in human immunodeficiency virus (HIV)-infected patients than in non-HIV-infected patients. Besides, there are substantial numbers of patients who cannot produce sputum, making the diagnosis of pulmonary tuberculosis (PTB) difficult.
To evaluate the relative yield of pre- and post-bronchoscopy sputum and bronchoalveolar lavage (BAL) in ‘sputum smear’-negative, HIV-positive patients.
A tertiary care referral hospital in Addis Ababa.
MATERIALS AND METHODS:
Acid-fast stain (AFS) using the concentration technique was done on 85 pre-bronchoscopy sputum and 120 BAL samples. Direct AFS was done on all BAL and 117 post-bronchoscopy sputum samples. Culture for Mycobacterium tuberculosis (MTB) was done for all sputa and BAL.
MTB was isolated from 26 (21.7%), 23 (19.7%) and 13 (15.3%) of BAL, post- and pre-bronchoscopy sputum cultures respectively. AFS on pre-bronchoscopy sputum using concentration technique and direct AFS on BAL together detected 11 (41%) of the 27 culture-positive cases. In patients who could produce sputum, the sensitivity of pre-bronchoscopy sputum culture (13/85, 15.3%) was comparable to BAL (12/85, 14%) and post-bronchoscopy sputum (12/85, 14%). In patients who could not produce sputum, however, both BAL (12/35, 40%) and post-bronchoscopy sputum (12/32, 31.4%) detected significantly more patients than those who could produce sputum (P=0.002, P=0.028 respectively).
In HIV-infected patients, AFS by concentration method on pre-bronchoscopy sputum and direct AFS on BAL in patients who cannot produce sputum are the preferred methods of making a rapid diagnosis. BAL culture seems to add little value in patients who can produce sputum; therefore, bronchoscopy should be deferred under such circumstances.
Acid-fast stain; bronchoalveolar lavage; concentration technique; M. tuberculosis; post-bronchoscopy; pre-bronchoscopy
To evaluate a commercially available antigen capture ELISA based on detecting lipoarabinomannan (LAM ELISA) in urine, for diagnosis of tuberculosis.
Consenting TB suspects and registering TB patients prospectively recruited from 3 hospitals were asked for 2 sputum specimens for microscopy and culture, urine for LAM testing, and blood for HIV testing, with radiological and clinical follow up for 2 months.
Of 427 participants, complete data were available from 397 (307 adult and 23 adolescent TB suspects, and 67 registering TB patients). HIV prevalence was 77%. TB was diagnosed in 195 (49%), including 161 culture-positive patients, and confidently excluded in 114 (29%) participants.
LAM ELISA sensitivity was 44% (95% CI 36-52%) for culture-confirmed TB (52% in smear-positive patients). Specificity was 89% (95% CI: 81-94%). Sensitivity was significantly higher in HIV-related TB (52%: 95%CI 43-62%, p <0.001) compared to HIV-negative TB (21%: 95%CI 9-37%), Sensitivity in smear-negative patients was low (28%: 95%CI 13-43% for combined HIV-positive and –negative patients).
Our findings confirm greater sensitivity of urine LAM detection for HIV-related TB. However, both sensitivity and specificity were suboptimal, suggesting that this version cannot confirm or exclude TB in either HIV-infected or uninfected patients.
Tuberculosis; diagnostic; culture; screening; Africa; HIV
To objectively assess the value of examining multiple sputum specimens in maximizing the sensitivity of detection of Mycobacterium tuberculosis, we retrospectively reviewed the acid-fast bacillus smear and culture results of patients diagnosed with culture-proven pulmonary tuberculosis (TB) at Hennepin County Medical Center between 1986 and 1996. Two hundred and forty six persons were diagnosed with pulmonary TB in the time period analyzed. In 93% of these cases (229 of 246) the laboratory diagnosis was made by detection of M. tuberculosis in sputum specimens; however, only 52% (120 of 229) of these patients had at least three sputum specimens submitted to the laboratory at the time of diagnosis. Of the patients from whom at least three specimens were collected, 47% (56 of 120) had at least one smear-positive specimen; the third or later specimen submitted was the first smear-positive specimen for 13% (7 of 56) of these persons but was the first culture-positive specimen for only 7% (4 of 56). Of the 64 patients with smear-negative specimens, for only 5% (3 of 64) was the third or subsequent specimen submitted the first from which M. tuberculosis was recovered. This data indicates that, in our institution, the overwhelming majority of culture-proven pulmonary TB cases are diagnosed from the first or second sputum specimen submitted to the laboratory and that only rarely is a third specimen of diagnostic value.
Fibreoptic bronchoscopy with bronchial aspiration* washings and biopsy was performed in 104 patients suspected clinically and radio logically of having pulmonary tuberculosis diagnostic yield in 9230% (96/104) cases. Diagnostic yield for tuberculosis was in 69.22% (72/104)cases, it includes positive aspiration and washings smear in 38.46%(40/l04) patients,positive mycobacteriai culture alone in 26.92% (28/104) casesandpositive biopsy in 3*84% (4/ 104) patients, Non-tuberculous conditions like pneumonia and bronchogenic carcinoma were diagnosed in 19.23% (20/104) cases and 3.84% (4/104) cases respectively. These results suggest that in areas with high prevalence of tuberculosis, bronchoscopy should be performed for early diagnosis and initiation of therapy in sputum smear-negative cases of pulmonary tuberculosis.
This work describes the experience at a tuberculosis clinical laboratory where relatively new TB diagnosis technologies; nucleic acid detection of two target strands, IS6110 and devR, by PCR and microscopic observation drug susceptibility (MODS) were used. The LJ culture was the gold standard. This evaluation was done from August 2007 to July 2009 on 463 sputum samples of tuberculosis suspects at a specialized tuberculosis clinic in Delhi, India.
None of the tests we evaluated can accurately detect the presence or absence of Mycobacterium tuberculosis in all the samples and smear microscopy was found to be the most reliable assay in this study.
The PCR assay could detect down to 2 pg of H37Rv DNA. Sensitivity, specificity was 0.40, 0.60 and 0.19, 0.81 for smear positive (n = 228) and negative samples (n = 235) respectively. In the MODS assay, sensitivity, specificity of 0.48, 0.52 and 0.38, 0.76 was observed for smear positive and negative samples. Sputum smear microscopy had sensitivity of 0.77 and specificity of 0.70.
Clinical suspects of pulmonary tuberculosis in which the sputum smears are
negative for acid fast bacilli represent a diagnostic challenge in resource
constrained settings. Our objective was to validate an existing
clinical-radiographic score that assessed the probability of smear-negative
pulmonary tuberculosis (SNPT) in high incidence settings in Peru.
We included in two referral hospitals in Lima patients with clinical
suspicion of pulmonary tuberculosis and two or more negative sputum smears.
Using a published but not externally validated score, patients were
classified as having low, intermediate or high probability of pulmonary
tuberculosis. The reference standard for the diagnosis of tuberculosis was a
positive sputum culture in at least one of 2 liquid (MGIT or Middlebrook
7H9) and 1 solid (Ogawa) media. Prevalence of tuberculosis was calculated in
each of the three probability groups.
684 patients were included. 184 (27.8%) had a diagnosis of pulmonary
tuberculosis. The score did not perform well in patients with a previous
history of pulmonary tuberculosis. In patients without, the prevalence of
tuberculosis was 5.1%, 31.7% and 72% in the low,
intermediate and high probability group respectively. The area under de ROC
curve was 0.76 (95% CI 0.72–0.80) and scores ≥6 had a
positive LR of 10.9.
In smear negative suspects without previous history of tuberculosis, the
clinical-radiographic score can be used as a tool to assess the probability
of pulmonary tuberculosis and to guide the decision to initiate or defer
treatment or to requesting additional tests.
The 2007 World Health Organization (WHO) guideline to diagnose smear-negative tuberculosis (TB) in HIV-prevalent settings was mainly based on expert advice and therefore requires evaluation in real life situations.
In 2009, this guideline was introduced at the ALERT hospital in Ethiopia. From October 2009 to January 2011, the accuracy of the guideline was evaluated using Mycobacterium tuberculosis culture positivity as reference standard in HIV positive TB suspects.
A total of 459 TB suspects were enrolled during the study period; 336 (73.2%) were HIV positive. Acid fast bacilli sputum smear microscopy was done for 74.7% (251/336) HIV positive TB suspects; 94.4% (237/251) were smear negative. A chest X-ray was performed in 92.8% (220/237) and a Mycobacterium tuberculosis culture in 63.7% (151/237). The median TB diagnostic delay for smear negative cases was 3 days (interquartile range 3–4 days). Of the 75 patients diagnosed with smear negative pulmonary TB, 89. 4% (67/75) were diagnosed by chest X-ray, 9.4% (7/75) by culture and 1.3% (1/75) by clinical suspicion only. In 147 smear negative TB suspects Mycobacterium tuberculosis culture and chest X-ray results were available. Among these 147 patients, the sensitivity of the chest X-ray to diagnose smear negative TB in HIV-positive TB suspects was 53.3% (95% CI: 26.7-78.7); the specificity 67.4% (95% CI: 58.7-75.3).
The 2007 WHO diagnostic algorithm for the diagnosis of smear negative TB is likely to reduce the diagnostic delay and therefore decrease morbidity and mortality of TB in a HIV prevalent settings like Ethiopia.
Smear negative; WHO; Tuberculosis; HIV; Diagnosis; Tuberculosis
Specimens from 495 patients attending Johannesburg hospitals and family planning clinics were examined for Trichomonas vaginalis by microscopy of Giemsa (GS), Papanicolaou (PAP), and acridine-orange (AO) stained smears, and by culture in Feinberg-Whittington medium. Culture, Pap and GS stained smears from vaginal swabs yielded fewer positives than AO stained smears. Although Pap-stained cytological smears gave the highest number of positives, in 30% of these cases the presence of T.vaginalis could not be confirmed by examination of vaginal swabs. Of the positive AO-stained smears, 93% were also positive by at least one other technique.
The diagnosis of extrapulmonary tuberculosis is difficult because of the paucibacillary nature of these infections. We developed a culture-enhanced PCR assay combining a preliminary step of broth culture in BacT/Alert MP bottles with the subsequent detection of Mycobacterium tuberculosis using the GenoType Mycobacteria Direct test. First, the procedure was applied to 10-fold-diluted suspensions of M. tuberculosis prepared in vitro. These experiments showed that a 15-day incubation time was required to detect bacilli in the suspension, with the lowest inoculum size yielding a single colony on Lowenstein-Jensen slants. The efficacy of culture-enhanced PCR at day 15 was subsequently evaluated with 225 nonrespiratory specimens from 189 patients with suspected tuberculosis. All these specimens were smear negative, and 31 (13.8%) from 27 patients were culture positive. The result of culture-enhanced PCR at day 15 was consistent with final culture results in all specimens tested. Compared to culture results, the sensitivity, specificity, positive predictive value, and negative predictive value were 100%. Four patients with a negative culture and a negative PCR result were diagnosed as having tuberculosis on the basis of histological findings or therapeutic response. When using a positive diagnosis of tuberculosis as a gold standard, the sensitivity, specificity, positive predictive value, and negative predictive value were 88.6%, 100%, 100%, and 97.9%, respectively. These results indicate that culture-enhanced PCR is a highly sensitive and specific method for the early detection of M. tuberculosis in extrapulmonary specimens.