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

• Published in: PloS one 2015-11, Vol.10 (11), p.e0141623-e0141623
• Main Authors: Bunyasi, Erick Wekesa, Tameris, Michele, Geldenhuys, Hennie, Schmidt, Bey-Marrie, Luabeya, Angelique Kany Kany, Mulenga, Humphrey, Scriba, Thomas J, Hanekom, Willem A, Mahomed, Hassan, McShane, Helen, Hatherill, Mark
• Format: Article
• Language: English
• Subjects: 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; 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
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0141623

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.