Treatment outcomes and factors associated with unfavourable outcome among previously treated tuberculosis patients with isoniazid resistance in four regions of Cameroon

Introduction: it is unclear what the optimal treatment regimen for previously treated patients with rifampicin-susceptible isoniazid resistant tuberculosis should be. Conflicting evidence exists as to the effectiveness of the WHO standardized category II regimen in these patients. The objectives were to compare treatment outcomes between previously treated rifampicin-susceptible pulmonary tuberculosis patients with and without isoniazid resistance using the category II regimen and determine factors associated with an unfavourable outcome in those with isoniazid resistance in four regions of Cameroon. Methods: we conducted a retrospective review of all bacteriologically confirmed previously treated rifampicin-susceptible patients with and without isoniazid resistance registered in four regions of Cameroon from January 2012 to March 2015. Results: a total of 753 patients with a mean age of 38 +/- 12 years including 498(66%) males were registered. Forty seven of the 753 had isoniazid-resistant TB, giving a prevalence of 6.2% (95% CI: 4.7-8.2). Treatment outcomes could only be ascertained for 733 patients as 20 (2.7%) were transferred out to other regions. Twenty-nine percent of patients with isoniazid resistance as against 21% of isoniazid susceptible patients had an unfavourable outcome (p = 0.32). In a multivariate logistic regression analysis, only HIV infection was significantly associated with an unfavourable outcome in isoniazid-resistant patients (p = 0.02). Conclusion: treatment outcomes using WHO category II regimen in previously treated rifampicin-susceptible pulmonary tuberculosis patients with and without isoniazid resistance in four regions of Cameroon are similar. HIV infection is an independent risk factor for an unfavourable outcome in patients with rifampicin-susceptible isoniazid-resistant disease treated with this regimen.