COST-EFFECTIVE STRATEGIES FOR ISONIAZID-BASED TUBERCULOSIS (TB) PREVENTIVE THERAPY FOR HIV-INFECTED ART-NAÏVE PATIENTS IN SOUTHERN INDIA

Purpose: Treatment of latent TB infection (tLTBI) is not currently recommended in India, despite TB being the most common opportunistic infection in HIV-infected patients.  We examine the clinical and economic impact of alternative strategies for tLTBI with isoniazid-based therapy in ART-naive HIV-infected patients in India.

Method: We used a state-transition model (the CEPAC-International model) simulating HIV/TB coinfection to investigate 4 tLTBI strategies: 1) no tLTBI, 2) tuberculin skin testing (TST) with tLTBI for TST+ patients, 3) tLTBI if TST+ or CD4 <200/µl, and 4) tLTBI for all HIV-infected patients.  Input data from India included a mean CD4 390/µl, TB incidence 9.55/100PY without and 2.11/100PY with tLTBI (tLTBI efficacy=78% reduction in TB incidence), and tLTBI cost $6.90/month (2008 US$ for a 6-month regimen of Ethambutol and Isoniazid daily); a single “line” of ART was available.  We incrementally compared the cost per life year saved (US$/YLS) among the strategies.  We examined the impact of less efficacious prophylaxis and availability of a second-line ART in sensitivity analyses.

Result: tLTBI for all HIV-infected patients maximized life expectancy (LE, 97.4 months), and lifetime costs ($2,490), and prevented the most acute TB cases.  The cost-effectiveness ratio for the tLTBI for all strategy was $620/YLS, very cost-effective by WHO criteria for India.

Strategy	Mean LE/person (months)	Mean cost/person (2008 US$)	$/YLS	TB cases /100 patients
1) No tLTBI	96.4	2460	--	66
2) tLTBI by TST status	96.9	2470	Dominated*	57
3) tLTBI by TST or CD4<200/µl	97.3	2480	350	48
4) tLTBI for all	97.4	2490	620	42
YLS = Year of life saved, *More costly and/or less effective compared to next least costly strategy

Decreasing the absolute efficacy of tLTBI by 20-60% increased the number of acute TB cases by 10-21/100 patients, decreased overall LE from 0.1-0.6 months, and altered the incremental cost-effectiveness of tLTBI for all from $660/YLS to $1,560/YLS.  The provision of second-line ART increased LE in the tLTBI for all strategy by 26.3 months but also increased lifetime acute TB cases by 1.7/100 patients; the incremental cost-effectiveness of tLTBI for all was $820/YLS.

Conclusion: Treatment of LTBI will improve clinical outcomes and be cost-effective when provided to ART-naïve HIV-infected patients in India, regardless of TST status or CD4 count.  Expansion of tLTBI is encouraged.