ORIGINAL ARTICLES

Induced sputum or gastric lavage for community-based diagnosis of childhood pulmonary tuberculosis?

M Hatherill^1,2, T Hawkridge^1,2,5, H J Zar², A Whitelaw^3,4, M Tameris^1,2, L Workman^1,2, L Geiter^5,6, W A Hanekom^1,2, G Hussey^1,2

¹ South African Tuberculosis Vaccine Initiative (SATVI), Institute of Infectious Disease and Molecular Medicine (IIDMM), University of Cape Town, Cape Town, South Africa
² School of Child and Adolescent Health, University of Cape Town, Cape Town, South Africa
³ Division of Laboratory Services, University of Cape Town, Cape Town, South Africa
⁴ National Health Laboratory Service, Johannesburg, South Africa
⁵ Aeras Global TB Vaccine Foundation, Rockville, MD, USA
⁶ Otsuka Pharmaceutical Development and Commercialization, Rockville, MD, USA

Dr M Hatherill, Room 2.09B, Wernher-Beit North, Faculty of Health Sciences, University of Cape Town, Anzio Road, Cape Town 7925, South Africa; mark.hatherill{at}uct.ac.za

Objectives: To compare the diagnostic yield of Mycobacterium tuberculosis from induced sputum (IS) and gastric lavage (GL) among children in a community setting.

Methods: Specimen-collection methods for bacteriological confirmation of pulmonary tuberculosis (PTB) were compared during a tuberculosis vaccine trial near Cape Town, South Africa (2001–2006). Children with a tuberculosis contact or compatible symptoms were investigated for suspected PTB. Diagnostic yields from 764 paired IS and GL specimens were compared in 191 culture-confirmed cases.

Measurements and main results: The crude yield of M tuberculosis was 10.4%, n = 108 by IS (5.8%) and n = 127 by GL (6.8%), from a total of 194 cases, of which three had incomplete IS/GL specimen pairs. Agreement between IS and GL was poor ( = 0.31). The comparative yield of a single IS sample (38%) was equivalent to a single GL sample (42%), with a difference in yield of –4% (95% CI –15% to +7%). The combined yield of same-day IS and GL specimens (67%) was equivalent to two consecutive GL specimens (66%), with a difference in yield of 1% (95% CI –9% to 11%), but significantly greater than two consecutive IS specimens (55%), with a difference in yield of 12% (95% CI 2% to 21%). The adjusted odds of a M tuberculosis culture were increased by a positive tuberculin skin test or chest radiograph compatible with PTB.

Conclusions: In this community setting, the diagnostic yield of a single IS sample was equivalent to that of a single GL sample. The optimal diagnostic yield may be obtained from paired IS and GL specimens taken on a single day or two GL specimens taken on consecutive days.

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