Background: Tuberculosis (TB) is the most common opportunistic infections among HIV-positive people in Africa. Although efficacious, there are several operational obstacles to implementing Isoniazid (INH) prophylaxis. This is the first study to estimate cost-effectiveness of INH prophylaxis in a routine health setting measuring actual TB cases averted among HIV individuals.
Method: HIV positive employees within a workplace health service were screened for active TB and offered INH where not contraindicated, according to a randomised incremental recruitment procedure. Financial and economic costs of implementing the intervention were estimated using retrospectively collected data and were incremental to voluntary counselling and testing services. TB cases averted were measured comparing the control and intervention periods.
Results: Of 1016 men screened for active TB, 679 started INH prophylaxis. 72% completed a 6 month course. TB incidence was reduced by 38% and 166 TB cases were averted. Screening for active TB and routine follow-up was 73% of total costs. The cost per person starting INH was US$27, excluding screening costs and $63 with screening. Cost per person completing INH prophylaxis was US$87 without screening, and US$120 with screening. Cost-effectiveness was US$353 per TB case averted. TB screening included a symptom questionnaire, chest x-rays and 2 sputum cultures. Routine monitoring included CD-4 counts. If only chest x-rays were used, the cost per TB case averted would be US$306 per TB case averted. Without routine CD-4 counts, the cost per TB case averted would be US $223.
Conclusions: INH prophylaxis can be cost-effective in routine health service settings in lower-resource settings. Screening and diagnostic monitoring can affect cost-effectiveness by up to 60%. In this setting, where average medical expenditures are US$1,736 per TB case treated and lost shifts by TB affected employees are estimated to be an additional US$410, INH prophylaxis is shown to be a significantly cost-saving intervention.
Kumaranayake, L.; Fielding, K.; Grant, A.; Roux, S.; Charalambous, S.; Day, J.; Churchyard, G. Cost-effectiveness of isoniazid preventive therapy of averting tuberculosis among HIV-infected employees in South Africa: Evaluation of a randomised intervention. Presented at XV International AIDS Conference (IAC), Bangkok, Thailand, 11-16 July, 2004. (2004)