Adherence to isoniazid preventive chemotherapy: a prospective community based study

Abstract

Background: Current international guidelines recommend 6-9 months of isoniazid (INH) preventive chemotherapy to prevent the development of active tuberculosis in children exposed to a susceptible strain of M tuberculosis. However, this is dependent on good adherence and retrospective studies have indicated that adherence to unsupervised INH preventive chemotherapy is poor.

Aim: To prospectively document adherence to six months of unsupervised INH monotherapy and outcome in children with household exposure to an adult pulmonary tuberculosis index case.

Methods: From February 2003 to January 2005 in two suburbs of Cape Town, South Africa, all children <5 years old in household contact with an adult pulmonary tuberculosis index case were screened for tuberculosis and given unsupervised INH preventive chemotherapy once active tuberculosis was excluded. Adherence and outcome were monitored.

Results: In total, 217 index cases from 185 households were identified; 274 children <5 years old experienced household exposure, of whom 229 (84%) were fully evaluated. Thirty eight children were treated for tuberculosis and 180 received preventive chemotherapy. Of the children who received preventive chemotherapy, 36/180 (20%) completed > or =5 months of unsupervised INH monotherapy. During the subsequent surveillance period six children developed tuberculosis: two received no preventive chemotherapy, and four had very poor adherence.

Conclusion: Adherence to six months of unsupervised INH preventive chemotherapy was poor. Strategies to improve adherence, such as using shorter duration multidrug regimens and/or supervision of preventive treatment require further evaluation, particularly in children who are at high risk to progress to disease following exposure.