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Kasa Tom S, Welch H, Kilalang C, Tefuarani N, Vince J, Lavu E, Johnson K, Magaye R, Duke T. Evaluation of Xpert MTB/RIF assay in children with presumed pulmonary tuberculosis in Papua New Guinea. Paediatr Int Child Health 2018; 38:97-105. [PMID: 28490246 DOI: 10.1080/20469047.2017.1319898] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
BACKGROUND The Gene Xpert MTB/ RIF assay (Xpert) is used for rapid, simultaneous detection of Mycobacterium tuberculosis (MTB) and rifampicin resistance. This study examined the accuracy of Xpert in children with suspected pulmonary tuberculosis (PTB). METHODS Children admitted to Port Moresby General Hospital with suspected PTB were prospectively enrolled between September 2014 and March 2015. They were classified into probable, possible and TB-unlikely groups. Sputum or gastric aspirates were tested by Xpert and smear microscopy; mycobacterial culture was undertaken on a subset. Children were diagnosed with TB on the basis of standard criteria which were used as the primary reference standard. Xpert, smear for acid-fast bacilli (AFB) and the Edwards TB score were compared with the primary reference standard. RESULTS A total of 93 children ≤14 years with suspected PTB were enrolled; 67 (72%) were classified as probable, 21 (22%) possible and 5 (5.4%) TB-unlikely. Eighty were treated for TB based on the primary reference standard. Xpert was positive in 26/93 (28%) MTB cases overall, including 22/67 (33%) with probable TB and 4/21 (19%) with possible TB. Three (13%) samples identified rifampicin resistance. Xpert confirmed more cases of TB than AFB smear (26 vs 13, p = 0.019). The sensitivity of Xpert, AFB smear and an Edwards TB score of ≥7 was 31% (25/80), 16% (13/80) and 90% (72/80), respectively, and the specificity was 92% (12/13), 100% (13/13) and 31% (4/13), respectively, when compared with the primary reference standard. CONCLUSION Xpert sensitivity is sub-optimal and cannot be relied upon for diagnosing TB, although a positive result is confirmatory. A detailed history and examination, standardised clinical criteria, radiographs and available tests remain the most appropriate way of diagnosing TB in children in resource-limited countries. Xpert helps confirm PTB better than AFB smear, and identifies rifampicin resistance. Practical guidelines should be used to identify children who will benefit from an Xpert assay.
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Key Words
- CPHL, Central Public Health Laboratory, PNG
- FLD, first-line drugs
- FNAB, fine-needle aspiration biopsy
- GA, gastric aspirate
- MDR TB, multidrug resistant tuberculosis
- MTB, Mycobacterium tuberculosis
- PMGH, Port Moresby General Hospital
- PNG, Papua New Guinea
- PTB, pulmonary tuberculosis
- Papua New Guinea
- QMRL, Queensland Mycobacterial Reference Laboratory, Australia
- SLD, second-line drugs
- TST, tuberculin skin test
- Tuberculosis
- Xpert
- children
- diagnostic
- resource-limited
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Affiliation(s)
- Sharon Kasa Tom
- a School of Medicine and Health Science , University of Papua New Guinea , Port Moresby , Papua New Guinea.,b Port Moresby General Hospital , Port Moresby , Papua New Guinea
| | - Henry Welch
- a School of Medicine and Health Science , University of Papua New Guinea , Port Moresby , Papua New Guinea.,b Port Moresby General Hospital , Port Moresby , Papua New Guinea.,c Baylor College of Medicine and Texas Children's Hospital , Houston , TX , USA
| | | | - Nakapi Tefuarani
- a School of Medicine and Health Science , University of Papua New Guinea , Port Moresby , Papua New Guinea.,b Port Moresby General Hospital , Port Moresby , Papua New Guinea
| | - John Vince
- a School of Medicine and Health Science , University of Papua New Guinea , Port Moresby , Papua New Guinea.,b Port Moresby General Hospital , Port Moresby , Papua New Guinea
| | - Evelyn Lavu
- d Central Public Health Laboratory , National Department of Health , Port Moresby , Papua New Guinea
| | - Karen Johnson
- d Central Public Health Laboratory , National Department of Health , Port Moresby , Papua New Guinea
| | - Ruth Magaye
- d Central Public Health Laboratory , National Department of Health , Port Moresby , Papua New Guinea
| | - Trevor Duke
- a School of Medicine and Health Science , University of Papua New Guinea , Port Moresby , Papua New Guinea.,e Department of Paediatrics , MCRI, Royal Children's Hospital, University of Melbourne , Victoria , Australia
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