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Evaluation of Xpert® MTB/RIF Assay in Induced Sputum and Gastric Lavage Samples from Young Children with Suspected Tuberculosis from the MVA85A TB Vaccine Trial.

ABSTRACT: Diagnosis of childhood tuberculosis is limited by the paucibacillary respiratory samples obtained from young children with pulmonary disease. We aimed to compare accuracy of the Xpert® MTB/RIF assay, an automated nucleic acid amplification test, between induced sputum and gastric lavage samples from young children in a tuberculosis endemic setting.We analyzed standardized diagnostic data from HIV negative children younger than four years of age who were investigated for tuberculosis disease near Cape Town, South Africa [2009-2012]. Two paired, consecutive induced sputa and early morning gastric lavage samples were obtained from children with suspected tuberculosis. Samples underwent Mycobacterial Growth Indicator Tube [MGIT] culture and Xpert MTB/RIF assay. We compared diagnostic yield across samples using the two-sample test of proportions and McNemar's ?2 test; and Wilson's score method to calculate sensitivity and specificity.1,020 children were evaluated for tuberculosis during 1,214 admission episodes. Not all children had 4 samples collected. 57 of 4,463[1.3%] and 26 of 4,606[0.6%] samples tested positive for Mycobacterium tuberculosis on MGIT culture and Xpert MTB/RIF assay respectively. 27 of 2,198[1.2%] and 40 of 2,183[1.8%] samples tested positive [on either Xpert MTB/RIF assay or MGIT culture] on induced sputum and gastric lavage samples, respectively. 19/1,028[1.8%] and 33/1,017[3.2%] admission episodes yielded a positive MGIT culture or Xpert MTB/RIF assay from induced sputum and gastric lavage, respectively. Sensitivity of Xpert MTB/RIF assay was 8/30[26.7%; 95% CI: 14.2-44.4] for two induced sputum samples and 7/31[22.6%; 11.4-39.8] [p = 0.711] for two gastric lavage samples. Corresponding specificity was 893/893[100%;99.6-100] and 885/890[99.4%;98.7-99.8] respectively [p = 0.025].Sensitivity of Xpert MTB/RIF assay was low, compared to MGIT culture, but diagnostic performance of Xpert MTB/RIF did not differ sufficiently between induced sputum and gastric lavage to justify selection of one sampling method over the other, in young children with suspected pulmonary TB.ClinicalTrials.gov NCT00953927.

SUBMITTER: Bunyasi EW

PROVIDER: S-EPMC4640848 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Evaluation of Xpert® MTB/RIF Assay in Induced Sputum and Gastric Lavage Samples from Young Children with Suspected Tuberculosis from the MVA85A TB Vaccine Trial.

Bunyasi Erick Wekesa EW Tameris Michele M Geldenhuys Hennie H Schmidt Bey-Marrie BM Luabeya Angelique Kany Kany AK Mulenga Humphrey H Scriba Thomas J TJ Hanekom Willem A WA Mahomed Hassan H McShane Helen H Hatherill Mark M

PloS one 20151110 11

<h4>Objective</h4>Diagnosis of childhood tuberculosis is limited by the paucibacillary respiratory samples obtained from young children with pulmonary disease. We aimed to compare accuracy of the Xpert® MTB/RIF assay, an automated nucleic acid amplification test, between induced sputum and gastric lavage samples from young children in a tuberculosis endemic setting.<h4>Methods</h4>We analyzed standardized diagnostic data from HIV negative children younger than four years of age who were investig ...[more]

PMID: 26554383

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Project description:BackgroundClinical tuberculosis diagnosis and empiric treatment have traditionally been common among patients with negative bacteriologic test results. Increasing availability of rapid molecular diagnostic tests, including Xpert MTB/RIF and the new Xpert Ultra cartridge, may alter the role of empiric treatment.MethodsWe prospectively enrolled outpatients age > = 15 who were evaluated for pulmonary tuberculosis at three health facilities in Kampala, Uganda. Using sputum mycobacterial culture, interviews, and clinical record abstraction, we estimated the accuracy of clinical diagnosis relative to Xpert and sputum culture and assessed the contribution of clinical diagnosis to case detection.ResultsOver a period of 9 months, 99 patients were diagnosed with pulmonary tuberculosis and subsequently completed sputum culture; they were matched to 196 patients receiving negative tuberculosis evaluations in the same facilities. Xpert was included in the evaluation of 291 (99%) patients. Compared to culture, Xpert had a sensitivity of 92% (95% confidence interval 83-97%) and specificity of 95% (92-98%). Twenty patients with negative Xpert were clinically diagnosed with tuberculosis and subsequently had their culture status determined; two (10%) were culture-positive. Considering all treated patients regardless of Xpert and culture data completeness, and considering treatment initiations before a positive Xpert (N = 4) to be empiric, 26/101 (26%) tuberculosis treatment courses were started empirically. Compared to sputum smear- or Xpert-positive patients with positive cultures, empirically-treated, Xpert-negative patients with negative cultures had higher prevalence of HIV (67% versus 37%), shorter duration of cough (median 4 versus 8 weeks), and lower inflammatory markers (median CRP 7 versus 101 mg/L).ConclusionJudged against sputum culture in a routine care setting of high HIV prevalence, the accuracy of Xpert was high. Clinical judgment identified a small number of additional culture-positive cases, but with poor specificity. Although clinicians should continue to prescribe tuberculosis treatment for Xpert-negative patients whose clinical presentations strongly suggest pulmonary tuberculosis, they should also carefully consider alternative diagnoses.

Project description:The aim of this study was to evaluate the performance of Xpert MTB/RIF Ultra (Ultra) compared with its predecessor, Xpert MTB/RIF (Xpert), in the diagnosis of tuberculosis (TB) in a low TB incidence country. Retrospective analysis was performed on 689 clinical samples received between 2015 and 2018, on which Xpert was performed, and on 715 samples, received between 2018 and 2020, on which Ultra was performed. Samples were pulmonary (n = 830) and extrapulmonary (n = 574) in nature, and a total of 264 were culture positive for Mycobacterium tuberculosis complex (MTBC). The diagnostic performance of both assays was analyzed using culture as the reference standard. The sensitivity of Ultra for culture positive (smear positive and smear negative) MTBC samples, was 93.2% (110/118) compared with 82.2% (120/146) for Xpert (P = 0.0078). In smear negative-culture positive samples, Ultra had a sensitivity of 74.2% (23/31) versus 36.11% (13/36) for Xpert (P = 0.0018). Specificity of both assays was comparable at 94.8% (566/597) for Ultra and 95.8% (520/543) for Xpert (P = 0.4475). The sensitivity of Ultra and Xpert assays among exclusively pulmonary samples was 95.3% (82/86) and 90.3% (84/93), respectively (P = 0.1955), and 87.5% (28/32) and 67.9% (36/53), respectively, among extrapulmonary samples (P = 0.0426). Ultra showed improved performance compared with Xpert in a low TB incidence setting, particularly in smear negative and extrapulmonary MTBC disease. The specificity of Ultra was lower than Xpert, however, this was not statistically significant. IMPORTANCE The study demonstrates the improved sensitivity of the Ultra compared with the Xpert, particularly in smear negative TB disease, for both pulmonary and extrapulmonary samples in a low TB incidence setting. Cycle threshold (Ct) value for both assays was found to positively correlate with time to TB culture positivity, suggesting that Ct and semiquantitative results could be used as indicators of sample MTBC bacillary burden, and thus, perhaps, of transmission potential. This may have implications for the designation of patient isolation precautions.

Dataset Information

Evaluation of Xpert® MTB/RIF Assay in Induced Sputum and Gastric Lavage Samples from Young Children with Suspected Tuberculosis from the MVA85A TB Vaccine Trial.

Publications

Evaluation of Xpert® MTB/RIF Assay in Induced Sputum and Gastric Lavage Samples from Young Children with Suspected Tuberculosis from the MVA85A TB Vaccine Trial.

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