Open Access Research article

La cuerda dulce – a tolerability and acceptability study of a novel approach to specimen collection for diagnosis of paediatric pulmonary tuberculosis

Felicia Chow1, Nora Espiritu2, Robert H Gilman13, Rosmery Gutierrez3, Sonia Lopez3, A Roderick Escombe134, Carlton AW Evans134 and David AJ Moore134*

Author Affiliations

1 Asociación Benéfica Proyectos en Informática, Salud, Medicina, y Agricultura (AB PRISMA), Lima, Perú

2 Hospital Nacional Dos de Mayo, Lima, Perú

3 Universidad Peruana Cayetano Heredia, Lima, Perú

4 Wellcome Trust Centre for Clinical Tropical Medicine, Imperial College London, UK

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BMC Infectious Diseases 2006, 6:67  doi:10.1186/1471-2334-6-67

Published: 4 April 2006



Recent data demonstrate the utility of the string test for the diagnosis of sputum-scarce HIV-associated TB in adults. We hypothesized that, if well-tolerated by children, this simple tool might offer a breakthrough in paediatric TB diagnosis. Thus the objective of this study, undertaken in the paediatric service of the Hospital Nacional Dos de Mayo, Lima, Perú, was to determine the tolerability and acceptability of the string test to paediatric TB suspects, their parents and nursing staff.


22 paediatric subjects aged 3–14 years (median 8) under investigation for TB were invited to undergo 2 string tests (four-hour downtime each). Subjective and objective pain and discomfort rating scales were used to assess the perception of the subject, parent and attending nurse.


Patients as young as 4 years tolerated the procedure extremely well with 84% willing to undergo a second procedure. Peak discomfort at the time of swallowing and of string retrieval was mild (30% of maximum possible score) and brief as judged by visual analogue ratings and objective indicators. Good concordance of parent/child and objective/subjective ratings strengthened the validity of these findings.


The string test is well tolerated and achievable for most paediatric TB suspects as young as 4 years. A formal prospective paediatric efficacy study is now needed.