Accuracy of the Xpert MTB/RIF test for the diagnosis of pulmonary tuberculosis in children admitted to hospital in Cape Town, South Africa: a descriptive study

• Published in: The Lancet infectious diseases 2011-11, Vol.11 (11), p.819-824
• Main Authors: Nicol, Mark P, Prof, Workman, Lesley, MSc, Isaacs, Washiefa, BSc, Munro, Jacinta, Black, Faye, MBBCh, Eley, Brian, FCPaed, Boehme, Catharina C, MD, Zemanay, Widaad, PhD, Zar, Heather J, Prof
• Format: Article
• Language: English
• Subjects: Age; Bacterial diseases; Bacterial diseases of the respiratory system; Biological and medical sciences; Child, Preschool; Children; Data processing; DNA, Bacterial - chemistry; DNA, Bacterial - genetics; Drug resistance; Drug Resistance, Multiple, Bacterial; Female; Hospitals; Human bacterial diseases; Human immunodeficiency virus; Humans; Infant; Infection; Infectious Disease; Infectious diseases; Liquid culture; Lung; Male; Medical research; Medical sciences; Microscopy; Mycobacterium; Mycobacterium tuberculosis - isolation & purification; Prospective Studies; Public health; Real-Time Polymerase Chain Reaction - methods; Sensitivity and Specificity; South Africa; Sputum; Sputum - microbiology; Statistics, Nonparametric; Tuberculosis; Tuberculosis and atypical mycobacterial infections; Tuberculosis, Pulmonary - diagnosis; Tuberculosis, Pulmonary - genetics; Tuberculosis, Pulmonary - microbiology
• ISSN: 1473-3099; 1474-4457
• DOI: 10.1016/S1473-3099(11)70167-0

Summary Background WHO recommends that Xpert MTB/RIF replaces smear microscopy for initial diagnosis of suspected HIV-associated tuberculosis or multidrug-resistant pulmonary tuberculosis, but no data exist for its use in children. We aimed to assess the accuracy of the test for the diagnosis of pulmonary tuberculosis in children in an area with high tuberculosis and HIV prevalences. Methods In this prospective, descriptive study, we enrolled children aged 15 years or younger who had been admitted to one of two hospitals in Cape Town, South Africa, with suspected pulmonary tuberculosis between Feb 19, 2009, and Nov 30, 2010. We compared the diagnostic accuracy of MTB/RIF and concentrated, fluorescent acid-fast smear with a reference standard of liquid culture from two sequential induced sputum specimens (primary analysis). Results 452 children (median age 19·4 months, IQR 11·1–46·2) had at least one induced sputum specimen; 108 children (24%) had HIV infection. 27 children (6%) had a positive smear result, 70 (16%) had a positive culture result, and 58 (13%) had a positive MTB/RIF test result. With mycobacterial culture as the reference standard, MTB/RIF tests when done on two induced sputum samples detected twice as many cases (75·9%, 95% CI 64·5–87·2) as did smear microscopy (37·9%, 25·1–50·8), detecting all of 22 smear-positive cases and 22 of 36 (61·1%, 44·4–77·8) smear-negative cases. For smear-negative cases, the incremental increase in sensitivity from testing a second specimen was 27·8% for MTB/RIF, compared with 13·8% for culture. The specificity of MTB/RIF was 98·8% (97·6–99·9). MTB/RIF results were available in median 1 day (IQR 0–4) compared with median 12 days (9–17) for culture (p