Journal Article

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

Mulenga, Humphrey, Bunyasi, Erick Wekesa, Tameris, Michele, Schmidt, Bey-Marrie, Geldenhuys, Hennie, Hatherill, Mark, Hanekom, Willem A., Mahomed, Hassan, Luabeya, Angelique Kany Kany, Scriba, Thomas J., McShane, Helen

2015

Overview

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 χ2 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.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Accuracy / Acquired immune deficiency syndrome / AIDS / Assaying / Automation / Bacteriological Techniques / Child, Preschool / Children / Children & youth / Childrens health / Culture / Data processing / Diagnostic systems / Double-Blind Method / Endemic Diseases / Female / Gastrointestinal Contents - microbiology / HIV / HIV Seronegativity / Human immunodeficiency virus / Humans / Immunization / Infant / Infectious diseases / Lavage / Lung diseases / Male / Medical diagnosis / Medicine / Mycobacterium tuberculosis - isolation & purification / Nucleic Acid Amplification Techniques / Nucleic acids / Organ Specificity / Pediatrics / Sampling methods / Sensitivity / Sensitivity analysis / Sensitivity and Specificity / South Africa - epidemiology / Sputum / Sputum - microbiology / Studies / Therapeutic Irrigation / Tuberculosis / Tuberculosis - diagnosis / Tuberculosis - epidemiology / Tuberculosis - microbiology / Tuberculosis Vaccines