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 for two induced sputum samples and 7/31 for two gastric lavage samples. Corresponding specificity was
893/893 and 885/890 respectively.
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.
Full article at: http://goo.gl/UOxgz8
By:
Erick Wekesa Bunyasi, Michele Tameris, Hennie Geldenhuys,
Bey-Marrie Schmidt, Angelique Kany Kany Luabeya, Humphrey Mulenga, Thomas J.
Scriba, Willem A. Hanekom, Mark Hatherill
South African Tuberculosis Vaccine Initiative, Institute of
Infectious Diseases and Molecular Medicine, and Department of Pediatrics and
Child Health, University of Cape Town, Cape Town, South Africa
Hassan Mahomed
Department of Health, Western Cape Province and Division of
Community Health, Stellenbosch University, Stellenbosch, South Africa
Helen McShane
Jenner Institute, Nuffield Department of Clinical Medicine,
University of Oxford, Oxford, United Kingdom
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