Amplified Mycobacterium Tuberculosis Direct Test Research Articles

Impact of nucleic acid amplification test on pulmonary tuberculosis notifications and treatments in Taiwan: a 7-year single-center cohort study

BackgroundNucleic acid amplification tests (NAAT) have been used as a diagnostic tool for pulmonary tuberculosis (PTB) in Taiwan for many years. In accordance with Taiwanese legislation, health care personnel are required to notify the Centers for Disease Control and Prevention (CDC) in case of suspected PTB. This study aimed to investigate the impact of NAAT(Gen-Probe) on the notification system for PTB and anti-tuberculosis treatments in Taiwan.MethodsA retrospective study on the impact of NAAT (Enhanced Amplified Mycobacterium tuberculosis Direct Test [E-MTD], Gen-Probe, San Diego, CA, USA) [NAAT(Gen-Probe)] was carried out at Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation from March 2011 to December 2017. During the study period, microscopic acid-fast-bacilli smears and mycobacterial cultures were available for PTB diagnosis. NAAT(Gen-Probe) was first introduced at the hospital in January 2014 for use as a diagnostic method for PTB. Positive sputum culture was considered as the gold standard for PTB diagnosis. We excluded clinically-diagnosed PTB cases.ResultsWhen NAAT(Gen-Probe) was applied, the rate of error notification to CDC decreased from 64.3 to 7.0% (P < 0.001), and unnecessary anti-TB treatments administered to suspected cases decreased from 14.9 to 6.5% (P = 0.005). In the non-PTB group, the mean duration of unnecessary anti-TB treatments changed from 38.9 ± 38.3 days to 37.0 ± 37.9 days (P = 0.874). In the PTB group, the mean time from notifying CDC to initiating treatment decreased from 3.05 ± 6.95 days to 1.48 ± 1.99 days (P = 0.004). The sensitivity, specificity, positive predictive value, and negative predictive value of NAAT(Gen-Probe) were 99.0, 92.3, 99.0, and 92.3%, respectively.ConclusionsUse of NAAT(Gen-Probe) led to decrease in the rate of error notification of suspected PTB cases to the CDC, avoidance of unnecessary use of anti-TB treatments, and accelerated initiation of appropriate treatments.

The new frontier of diagnostics: Molecular assays and their role in infection prevention and control.

Recent advances in technology over the last decade have propelled the microbiology laboratory into a pivotal role in infection prevention and control. The rapid adaptation of molecular technologies to the field of clinical microbiology now greatly influences infectious disease management and significantly impacts infection control practices. This review discusses recent developments in molecular techniques in the diagnosis of infectious diseases. It describes the basic concepts of molecular assays, discusses their advantages and limitations, and characterizes currently available commercial assays with respect to cost, interpretive requirements, and clinical utility.

Exudative pleural effusion in chronic kidney disease: An aetiological dilemma.

Exudative pleural effusion in chronic kidney disease: An aetiological dilemma.

Negative Mantoux test in a patient with definite pulmonary and ocular tuberculosis

The case is reported of a patient with pulmonary and ocular tuberculosis presenting with blurred vision in both eyes. A 27-year-old well-nourished male nursing-home resident with a previous history of traumatic intracerebral hemorrhage was brought to the ophthalmological clinic due to progressively blurred vision. His best-corrected visual acuity was 20/400 in the right eye with only light perception in the left eye. Fundus examinations revealed retinal segmental periphlebitis and hemorrhagic retinitis in the right eye and dense vitreous hemorrhage in the left eye. The Mantoux test was negative; however, the results of an interferon gamma release assay were positive. Ocular tuberculosis was suspected. Although he had never had any respiratory symptoms, his chest radiograph and computed tomography scan showed a multiple centrilobular glandular and ground-glass appearance with air-space consolidations and atelectasis in both lower lobes. Pulmonary tuberculosis was confirmed by a positive acid-fast stain of a bronchial alveolar lavage sample. A GEN-PROBE amplified Mycobacterium tuberculosis direct test of the vitreous fluids was also positive. Ocular tuberculosis was confirmed. After treatment for tuberculosis and vitrectomies, his final best-corrected visual acuity improved to 20/30 in the right eye and 20/200 in the left eye. Ocular tuberculosis is rarely reported as the primary presentation of systemic tuberculosis in young patients. A negative Mantoux test may lead to misdiagnosis and delayed treatment. Doctors should become more familiar with the manifestations of systemic tuberculosis and use advanced diagnostic tools in cases of clinical suspicion.

Use of amplified Mycobacterium tuberculosis direct test in respiratory samples from HIV-infected patients in Brazil

OBJECTIVE: To compare the accuracy of the amplified Mycobacterium tuberculosis direct (AMTD) test with reference methods for the laboratory diagnosis of tuberculosis in HIV-infected patients. METHODS: This was a study of diagnostic accuracy comparing AMTD test results with those obtained by culture on Löwenstein-Jensen (LJ) medium and by the BACTEC Mycobacteria Growth Indicator Tube 960 (BACTEC MGIT 960) system in respiratory samples analyzed at the Bioassay and Bacteriology Laboratory of the Oswaldo Cruz Foundation Evandro Chagas Clinical Research Institute in the city of Rio de Janeiro, Brazil. RESULTS: We analyzed respiratory samples collected from 118 patients, of whom 88 (74.4%) were male. The mean age was 36.6 ± 10.6 years. Using the AMTD test, the BACTEC MGIT 960 system, and LJ culture, we identified M. tuberculosis complex in 31.0%, 29.7%, and 27.1% of the samples, respectively. In comparison with LJ culture, the AMTD test had a sensitivity, specificity, positive predictive value, and negative predictive value of 87.5%, 89.4%, 75.7%, and 95.0%, respectively, for LJ culture, whereas, in comparison with the BACTEC MGIT 960 system, it showed values of 88.6%, 92.4%, 83.8%, and 94.8%, respectively. CONCLUSIONS: The AMTD test showed good sensitivity and specificity in the population studied, enabling the laboratory detection of M. tuberculosis complex in paucibacillary respiratory specimens.

The predictive value of Gen-Probe's amplified Mycobacterium tuberculosis direct test compared with culturing in paraffin-embedded lymph node tissue exhibiting granulomatous inflammation and negative acid fast stain

The diagnosis of granulomatous inflammation with possible tuberculosis (TB) infection in histopathology is often difficult. There is a need for a rapid and reliable diagnostic test. Thus, we evaluated the performance of the Mycobacterium tuberculosis direct (MTD) test in specimens with granulomatous lymphadenitis and negative acid fast stains. The M. tuberculosis direct (MTD) test by Gen-Probe was performed on 45 formalin-fixed paraffin-embedded tissue samples including 34 lymph nodes. We measured the predictive values of the MTD test in specimens with granulomatous lymphadenitis and negative acid fast stains. The overall test sensitivity was 73.9%, and specificity was 95.4%. The MTD test sensitivity and specificity for lymph node tissue were 72.7% and 91.67%, respectively. In the presence of granulomatous inflammation, the MTD test sensitivity and specificity were higher than those for all tissue samples, at 75% and 100%, respectively. Based on this study, the MTD test should be used as a supportive test in addition to conventional histochemical or immunological staining methods when evaluating lymph node tissue with a granulomatous inflammation to deliver stronger evidence to support clinical decisions at a much earlier time than a culture would allow.

Use of amplified Mycobacterium tuberculosis direct test (Gen-probe Inc., San Diego, CA, USA) in the diagnosis of tubercular synovitis and early arthritis of knee joint

Background:The diagnosis of knee joint tuberculosis, especially in early stages of synovial disease, has more often been based on clinicoradiological suspicion, with no single test claiming to be a dependable rapid diagnostic test with high sensitivity and specificity. Nuclear amplification tests in vogue like the polymerase chain reaction have shown variable sensitivity and false positivity rates in various studies. We evaluated the role of Amplified Mycobacterium tuberculosis Direct Test (AMTDT) or Genprobe in the diagnosis of knee joint tuberculosis in early, especially, early synovitis and arthritis cases.Patients and Methods:Thirty two patients of suspected knee joint tuberculosis were subjected to diagnostic arthroscopy during the study period. The synovial fluid and tissue were subjected to mycobacterial culture, histopathology, and AMTDT. A comparative analysis of the sensitivity and specificity of this new test with culture and histopathology was done and the time taken for reporting was calculated for each test.Results:Out of 32 tissue samples, 8 were found to be positive with mycobacterial culture [Lowenstein Jensen (LJ)/Bactec], 11 were positive with histopathology, and 5 were found to positive with AMTDT. The sensitivity of AMTDT was found to be 62.5% and specificity was 100% with a P value of 0.083. The results were obtained earliest with AMTDT with a mean reporting time of 1.2 days, while the results of histopathology were obtained in a mean time of 6.8 days, BacT alert in 22.5 days, and conventional LJ medium culture results in 48.6 days.Conclusion:AMTDT or Genprobe is a rapid diagnostic test for early diagnosis of tubercular arthritis, but has low sensitivity in knee joint tuberculosis. Nuclear amplification tests are still far from being a single promising alternative to conventional tests in cases of joint tuberculosis. Routine use of arthroscopic biopsies in all suspected cases is helpful in the early diagnosis of knee joint tuberculosis.

Amplified Mycobacterium Tuberculosis Direct Test for Diagnosing Tuberculous Pleurisy—A Diagnostic Accuracy Study

BackgroundThe study was designed to investigate the clinical usefulness of Amplified Mycobacterium Tuberculosis Direct (AMTD) tests for diagnosing TB pleurisy.MethodsOne hundred and fifty-two patients for whom the exclusion of tuberculous pleural effusion was necessary were retrospectively analyzed.ResultsThe sensitivity of AMTD in diagnosing pleural TB was 36.4% (20 of 55). Combining sputum and pleural effusion AFB smear, pleural biopsy, and AMTD test of pleural effusion increased sensitivity to 82.5% (33/40). There were significantly higher percentages of neutrophils in the pleural effusion in the positive than in the negative AMTD group (38.0±6.7% vs. 11.1±3.7%, p<0.001). Patients with symptom duration <18 days prior to pleural effusion studies had more positive AMTD tests than those with symptom >18 days (70% vs. 31.4%; OR 5.09; 95% CI 1.54–16.79; p = 0.011).ConclusionsCombining AMTD tests with conventional diagnostic methods offer good sensitivity for pleural TB diagnosis. Patients in the early course of the disease are better candidates for AMTD tests.

Evaluation of the results of Mycobacterium tuberculosis direct test (MTD) and Mycobacterial culture in urine samples

Tuberculosis remains a public health problem in Turkey. Rapid detection of Mycobacterium tuberculosis plays a key role in control of infection. In this article, the Gen-Probe Amplified Mycobacterium Tuberculosis Direct Test (MTD) was evaluated for detection of M. tuberculosis in urine samples. The performance of the MTD was very good and appropriate for routine laboratory diagnosis.

Clinical Evaluation of Gen-Probe's Amplified Mycobacterium Tuberculosis Direct Test for Rapid Diagnosis of Mycobacterium tuberculosis in Egyptian Children at Risk for Infection

Diagnostic detection of tuberculosis (TB) has improved considerably. Available, standardized, nucleic acid-based amplification techniques have been shown to yield reliable results within 4 to 7 hours of sample processing. To study the diagnostic performance of Gen-Probe's technique for direct detection of Mycobacterium tuberculosis in comparison with BACTEC 460 TB culture for both positive and negative Ziehl-Neelsen smears in Egyptian children at risk for TB infection. We prospectively evaluated 50 children from families with a positive history of TB. All patients were referred from outpatient clinics of the Mansoura University Children's Hospital, Egypt. The children had a positive tuberculin skin test with an induration diameter of more than 10 mm and had scars from a bacille Calmette-Guérin vaccination within the past 2 years. Three consecutive sputum samples were taken from each patient. The samples were examined to detect M. tuberculosis by means of the Gen-Probe technique, direct smear microscopy, and bacterial culture by BACTEC 460 TB. Of the 50 cases, 30 (60%) had sputum samples that were positive for TB by BACTEC 460 TB culture, and 29 cases (58%) were positive by the Gen-Probe technique. Sensitivity and specificity of Ziehl-Neelsen smears was 83.3% and 100%, respectively, with overall accuracy of 90%. Sensitivity and specificity of the Gen-Probe technique were 96.7% and 100%, respectively, with overall accuracy of 98%. The results of this study suggest that the Gen-Probe technique is an accurate method for rapid detection of M. tuberculosis complexes in respiratory samples from children at risk for TB. It can be used for diagnosis of smear-negative cases that are suspect for TB.

Clinical evaluation of Gen-Probe's amplified mycobacterium tuberculosis direct test for rapid diagnosis of Mycobacterium tuberculosis in Egyptian children at risk for infection.

Abstract Context.—Diagnostic detection of tuberculosis (TB) has improved considerably. Available, standardized, nucleic acid–based amplification techniques have been shown to yield reliable results within 4 to 7 hours of sample processing. Objective.—To study the diagnostic performance of Gen-Probe's technique for direct detection of Mycobacterium tuberculosis in comparison with BACTEC 460 TB culture for both positive and negative Ziehl-Neelsen smears in Egyptian children at risk for TB infection. Design.—We prospectively evaluated 50 children from families with a positive history of TB. All patients were referred from outpatient clinics of the Mansoura University Children's Hospital, Egypt. The children had a positive tuberculin skin test with an induration diameter of more than 10 mm and had scars from a bacille Calmette-Guerin vaccination within the past 2 years. Three consecutive sputum samples were taken from each patient. The samples were examined to detect M tuberculosis by means of the Gen-Probe t...

Use of the Amplified Mycobacterium tuberculosis Direct Test in a Public Health Laboratory: Test Performance and Impact on Clinical Care

The Amplified Mycobacterium tuberculosis Direct Test (MTD; Gen-Probe; San Diego, CA) is a nucleic-acid amplification test for rapid pulmonary tuberculosis (PTB) diagnosis. In a routine public health setting, test accuracy and impact on clinical decisions are unknown.Retrospectively, we evaluated MTD accuracy and impact on clinical decisions in a public health setting. To estimate MTD accuracy, mycobacterial culture was used as the "gold standard." To evaluate MTD impact on clinical decisions, concordance of clinician presumptive diagnosis (at time of MTD and smear availability) and definitive diagnosis, and duration of nonindicated tuberculosis therapy were determined for smear-positive PTB suspects in a period of MTD availability (MTD group) and a prior period of MTD nonavailability (non-MTD group).A total of 1,151 respiratory specimens from 638 PTB suspects were analyzed. MTD sensitivity, specificity, positive predictive value, and negative predictive value were 91.7%, 98.7%, 96.7%, and 96.5% overall, respectively; and 98.7%, 97.8%, 98.7%, and 97.8% for smear-positive patients; and 62.2%, 98.9%, 85.2%, and 96.1% for smear-negative patients. In the MTD group, concordance between definitive and clinician presumptive diagnoses was 78% (95% confidence interval [CI], 64 to 88%), similar to that for the non-MTD group (79%; 95% CI, 68.4 to 89.6%). However, concordance between definitive diagnosis and the MTD test was 98% (95% CI, 94.1 to 100%). Median duration of nonindicated tuberculosis treatment was 6 days for the MTD group vs 31 days for the non-MTD group (p = 0.002).In this public health setting, MTD was accurate and rapidly detected more than half of the smear-negative PTB cases. For smear-positive PTB suspects, MTD had excellent concordance with definitive diagnosis, but clinicians often inappropriately initiated TB therapy despite a negative MTD result.

Development of active tuberculosis following initiation of infliximab despite appropriate prophylaxis

Sir, Prospective cohort studies have demonstrated an increased risk of active tuberculosis in patients treated with tumor necrosis factor antagonists (anti-TNF agents) [1]. Current guidelines support chemoprophylaxis with isoniazid (INH) for 6–9 months prior to the initiation of anti-TNF agents in patients with evidence of latent tuberculosis [2]. We present two rheumatoid arthritis patients who had positive tuberculin skin tests (TST). Despite receiving an adequate course of INH for latent tuberculosis infection, both patients developed active tuberculosis after initiation of infliximab. Patient 1 is a 58-yr-old male Chinese immigrant with a 3 yr history of seropositive rheumatoid arthritis who was admitted to the hospital with three weeks of fevers, chills, productive cough, night sweats and altered mental status. His medical history was otherwise notable for chronic inactive hepatitis B and chronic obstructive pulmonary disease. Three yrs prior, he had a positive TST. Chest computed tomography (CT) revealed emphysematous changes and multiple calcified granulomas consistent with prior tuberculosis. He was treated with a 9 month course of INH, 300 mg/day. Despite treatment with methotrexate and sulfasalazine, his rheumatoid arthritis remained active, requiring frequent intra-articular steroid injections and oral corticosteroids. Fourteen months prior to admission he started infliximab infusions (6 mg/kg) in addition to methotrexate and sulfasalzine, and was successfully tapered off corticosteroids. On admission, the patient was ill appearing and thin. He had a temperature of 102.6° with normal respiratory rate and oxygen saturation. The breath sounds were decreased and there were diffuse expiratory wheezes in all the lung fields. There was no lymphadenopathy. Initial investigations included normal complete blood counts, electrolytes, liver and renal function tests, as well as negative tests for HIV, hepatitis C and rapid plasma reagent. Sputum stains for acid-fast bacilli, pneumocystis carinii and legionella species were negative. A chest radiograph and chest CT scan demonstrated no new infiltrates or pathological lymphadenopathy. A CT scan of the abdomen and pelvis revealed enlarged mesenteric and retro-peritoneal nodes. Bone marrow biopsy and right inguinal lymph node biopsy did not show evidence of malignancy or granulomatous disease. Given the high level of concern for tuberculosis, the patient was empirically started on INH, rifampin, pyrizinamide and ethambutol. Nine days after discharge the sputum cultures grew mycobacterium tuberculosis, with sensitivity to ethambutol, INH, pyrazinamide, rifampin and streptomycin. He has since made a full recovery. Patient 2 is a 77-yr-old woman originally from Trinidad with seronegative rheumatoid arthritis treated with infliximab who was admitted to the hospital with a three week history of worsening weakness and fatigue. One week prior to admission she developed a non-productive cough, fevers and chills. On the day of admission she was profoundly weak and was noted by family members to have slurred speech. Her medical history was also notable for sickle cell trait, glucose-6-phosphate dehydrogenase deficiency, sideroblastic anaemia and a single episode of bilateral pulmonary embolism. Ten yrs prior she had a positive TST; chest radiographs did not show any abnormalities suggestive of tuberculosis at the time. Seven yrs prior to admission she was treated with a 7 month course of INH after starting prednisone. She had a negative TST 4 yrs prior. She had previously failed methotrexate and subsequently failed combination therapy with leflunomide. She was started on treatment with infliximab at 4 mg/kg every 6 weeks 4 months earlier. Medications on admission included methotrexate (17.5 mg orally once per week), prednisone (5 mg/day), infliximab, warfarin and oxycodone. On admission, her temperature was 103 F and oxygen saturation was 92%. On chest auscultation, there were inspiratory crackles at the left lower lung base. She had right hip pain with very limited range of motion. Initial laboratory evaluation was notable for a white blood cell count of 2600 cells, with 59% neutrophils and 9% bands. Serum electrolytes were normal; blood and urine cultures were negative. A chest radiograph was consistent with left lower lobe pneumonia and the patient was initially treated for community-acquired pneumonia with levofloxacin. By the fourth hospital day she had failed to improve; a chest CT demonstrated bilateral multiple small pulmonary nodules consistent with miliary tuberculosis. A right hip joint aspiration yielded sterile, non-inflammatory synovial fluid. A bone marrow biopsy showed normal myeloid elements. On the ninth hospital day a sputum sample was positive by gen-probe amplified mycobacterium tuberculosis direct test. Treatment was started with rifampin, INH, ethambutol and pyrazinamide. The following day she developed respiratory failure requiring mechanical ventilation for the next 9 days. She gradually recovered and was discharged to a rehabilitation facility after a 34 day hospital course. Eventually, sputum cultures grew mycobacterium tuberculosis, with sensitivity to ethambutol, INH, pyrazinamide, rifampin and streptomycin.

Performances du test « Amplified Mycobacterium tuberculosis Direct Test » sur les échantillons respiratoires et extrarespiratoires

From March 1998 to December 2004, 3641 specimens (2427 respiratory samples and 1214 non-respiratory samples) collected from 2079 patients, were tested using the «Gen-Probe Amplified Mycobacterium tuberculosis Direct Test» (AMTD). After decontamination procedure every sample was testing by AMTD and by culture on solid and liquid media. The «Gold-standard» was considered by the combination of culture results and clinical diagnosis. Respiratory tuberculosis was present in 9,7% (127 patients), and non-respiratory tuberculosis was present in 18,9% (170 patients, mostly originated from Africa). Among the 2427 respiratory samples (197 culture positive samples, 211 AMTD positive) 225 corresponded to tuberculosis; for the 1214 non-respiratory samples (184 culture positive samples, 213 AMTD positive) 231 corresponded to tuberculosis. After resolving the discordant results, the sensitivity, specificity, positive and negative predictive values were 93.8, 100, 100, 99.4% respectively for respiratory samples and 92.2, 99.9, 99.5, 98% for non respiratory samples.

Brote epidémico de tuberculosis en una guardería de Zaragoza

To describe the clinical and radiological features, diagnosis, and treatment of an epidemic outbreak of tuberculosis in a daycare centre in Zaragoza. The index case was a teaching assistant with a late diagnosis of bacilliferous tuberculosis. Mantoux testing was carried out in all children. In those with a positive Mantoux test, a chest X-ray was performed. Children with an abnormal chest X-ray underwent microbiological investigations. Among all the children in the daycare center, the Mantoux test was positive in 11 children. Chest X-ray was abnormal in 10 children. Of these, seven (70 %) were symptomatic. Chest X-ray showed dense opacification in nine children (90 %) and mediastinal lymph adenopathy in five (50 %). Three children (30 %) had lobar atelectasis requiring bronchoscopy and subsequent steroid therapy. Bacilloscopy was positive in only one child. Gastric juice culture was positive in seven children and the amplified Mycobacterium tuberculosis direct test was positive in a further seven. All microbiological investigations were negative in only one child. Establishing a definitive diagnosis of tuberculosis in children remains difficult and frequently relies on a constellation of clinical findings, radiology and epidemiology in children with a positive Mantoux test. The amplified Mycobacterium tuberculosis direct test has high sensitivity and provides fast results. Epidemic outbreaks continue to be frequent in Spain. Study of contacts shows high efficiency in controlling outbreaks.

Comparison of real-time polymerase chain reaction using the Smart Cycler and the Gen-Probe amplified Mycobacterium tuberculosis direct test for detection of M. tuberculosis complex in clinical specimens

The performance of a real-time polymerase chain reaction (PCR) assay using the Smart Cycler instrument and a minor groove binding MGB Eclipse™ probe (Epoch Biosciences, Bothell, WA) for identification of Mycobacterium tuberculosis complex in acid-fast bacillus smear-positive and smear-negative clinical specimens was assessed by comparing results to the Amplified M. tuberculosis Direct Test (MTD) and mycobacterial culture plus clinical diagnosis. After initial testing, the overall sensitivity, specificity, and positive and negative predictive values of PCR for the 172 specimens submitted for mycobacterial culture were 86.3%, 100%, 100%, and 94.5%, respectively. These same values for MTD were 98.0%, 99.2%, 98.0%, and 99.2%. For 83 additional specimens, only MTD and PCR were performed; 5 specimens were positive and 78 were negative by both tests. The sensitivity of the PCR assay was improved by using different primers and probes. The time to a result for real-time PCR, starting with a decontaminated sample, was less than 3 h compared with 5–6 h for the MTD.

Valoración de la prueba de amplificación MTD-2 para la detección directa de Mycobacterium tuberculosis en la muestra

To evaluate the utility of the Amplified Mycobacterium Tuberculosis Direct Test (MTD-2, Gen-Probe) in the microbiological diagnosis of tuberculosis. We evaluated the results obtained in 146 specimens with the MTD-2 test, together with those of the culture and smears. The MTD-2 test was performed on all the smear positives specimens (n=47), on the smear-negative specimens, when the test was demanded (n=19), and in other smear-negative specimens previously selected, according to the clinical history of the patient (n=80). We considered real cases of tuberculosis, those that were culture positive for Mycobacterium tuberculosis and those that were specifically treated. The overall sensitivity, specificity, positive and negative predictive values for the MTD test were: 95, 76, 71, and 96%, for the culture; and 84, 100, 100 and 90% and 75, 94, 89 and 86% for the smears, respectively. In smear positive specimens, the test showed a great specificity, and differentiated M. tuberculosis from other mycobacteria. In the smear negatives, the sensitivity of the test was low and so was the positive predictive value, especially in series performed with a high work load. Data from our study show that the MTD-2 test is a reliable method for rapid diagnosis of tuberculosis in smear positive specimens. However, due to its low sensitivity and positive predictive value, it is not recommended in the routine diagnosis of tuberculosis. Also, for this reason, whenever a positive result is obtained with a smear negative specimen, the result needs to be confirmed with another specimen.

Clinical Evaluation of the Gen-Probe Amplified Mycobacterium Tuberculosis Direct Test for Rapid Diagnosis of Tuberculosis Lymphadenitis

This prospective study evaluated the performance of the Amplified Mycobacterium Tuberculosis Direct Test (MTD) for the diagnosis of lymph node tuberculosis in Djibouti, Republic of Djibouti. Of 197 specimens sampled from 153 patients, 123 were from 95 tuberculous patients. The sensitivity and specificity of MTD were 93 and 100%, respectively. The sensitivity of culture was 89%.

Evaluation of a Modified Gen-Probe Amplified Direct Test for Detection of Mycobacterium tuberculosis Complex Organisms in Cerebrospinal Fluid

Laboratory evidence for tuberculous meningitis is difficult to acquire due to the low numbers of organisms present in cerebrospinal fluid (CSF) and the presence of nucleic acid amplification inhibitors. The Amplified Mycobacterium tuberculosis Direct Test (MTD) is sensitive and specific for the direct detection of M. tuberculosis complex in respiratory samples but has not been approved for CSF. We evaluated a modified version of the current MTD, optimized for use with CSF samples. Samples were prepared by spiking CSF with various numbers of M. tuberculosis complex organisms. The modified MTD performance was compared with results obtained using a purified RNA sample extracted using the Qiagen RNeasy Protect Bacteria Mini Kit. By use of CSF artificially spiked with M. tuberculosis complex, the sensitivity of the modified MTD was 100% (six of six) for CSF samples containing approximately 600 CFU/ml, 78% (seven of nine) for approximately 60 CFU/ml, 50% (three of six) for 6 CFU/ml, and 17% (one of six) for samples with <1 CFU/ml. The specificity of the modified MTD method was 100% (22 of 22). The sensitivity of the Qiagen MTD method was 100% for CSF samples containing approximately 600 CFU/ml (six of six) and approximately 60 CFU/ml (nine of nine), 50% for samples with approximately 6 CFU/ml (three of six), and 50% for samples with <1 CFU/ml (three of six). The specificity of the Qiagen MTD method was 86% (19 of 22). With the Qiagen MTD method, however, initial results were equivocal for 14 of the 27 (52%) positive samples, requiring repeat analysis, whereas with the modified MTD, only 1 of 27 (4%) was equivocal. The modified MTD for CSF samples was less time-consuming and less expensive and resulted in considerably fewer equivocal results than the Qiagen MTD method did.

Mycobacterium celatum, an emerging pathogen and cause of false positive amplified mycobacterium tuberculosis direct test

Mycobacterium celatum is a recently described organism. Herein we describe a case of M. celatum lymphadenitis in an immunocompetent child and the first reported case of a M. celatum infection (lung abscess) in a transplant recipient. A literature review identified 19 other cases of M. celatum infection. Fifteen occurred in patients with the acquired immunodeficiency syndrome. Of these, nine were disseminated and six were localized (primarily to the lungs). The remaining 4 patients were immunocompetent and had localized infection (pneumonitis or lymphadenitis). Diagnosis of M. celatum infection can be challenging as M. celatum can cause false-positive results with the current version of the Amplified Mycobacterium tuberculosis Direct Test (Gen-Probe, San Diego, CA.). Definitive identification is available by DNA sequencing or high-performance liquid chromatography. M. celatum can cause infection in immunocompromised and immunocompetent hosts.