Cost-effectiveness of WHO-Recommended Algorithms for TB Case Finding at Ethiopian HIV Clinics

Abstract

Background: The World Health Organization (WHO) recommends active tuberculosis (TB) case finding and a rapid molecular diagnostic test (Xpert MTB/RIF) to detect TB among people living with HIV (PLHIV) in high-burden settings. Information on the cost-effectiveness of these recommended strategies is crucial for their implementation.

Methods: We conducted a model-based cost-effectiveness analysis comparing 2 algorithms for TB screening and diagnosis at Ethiopian HIV clinics: (1) WHO-recommended symptom screen combined with Xpert for PLHIV with a positive symptom screen and (2) current recommended practice algorithm (CRPA; based on symptom screening, smear microscopy, and clinical TB diagnosis). Our primary outcome was US$ per disability-adjusted life-year (DALY) averted. Secondary outcomes were additional true-positive diagnoses, and false-negative and false-positive diagnoses averted.

Results: Compared with CRPA, combining a WHO-recommended symptom screen with Xpert was highly cost-effective (incremental cost of $5 per DALY averted). Among a cohort of 15 000 PLHIV with a TB prevalence of 6% (900 TB cases), this algorithm detected 8 more true-positive cases than CRPA, and averted 2045 false-positive and 8 false-negative diagnoses compared with CRPA. The WHO-recommended algorithm was marginally costlier ($240 000) than CRPA ($239 000). In sensitivity analysis, the symptom screen/Xpert algorithm was dominated at low Xpert sensitivity (66%).

Conclusions: In this model-based analysis, combining a WHO-recommended symptom screen with Xpert for TB diagnosis among PLHIV was highly cost-effective ($5 per DALY averted) and more sensitive than CRPA in a high-burden, resource-limited setting.

Keywords: Ethiopia; TB/HIV co-infection; cost-effectiveness; developing countries; modeling.

Figure 1.

Decision analysis model for tuberculosis screening and diagnosis among patients at Ethiopian HIV clinics. Decision analytic model with 2 different strategies for TB screening and diagnosis among PLHIV: (1) Symptom screen/Xpert (“SSX”) combines a World Health Organization–recommended symptom screen (cough, fever, night sweats, weight loss) with Xpert as the initial diagnostic test for PLHIV with a positive symptom screen (ie, having at least 1 symptom) [1, 12]. (2) Current practice screens patients with the symptom screen, and then combines smear microscopy with clinical diagnosis for those with negative smear microscopy results. Squares represent decision nodes, circles represent chance nodes, and triangles represent terminal nodes. The number listed under each arm is the probability of progressing to that arm (from prior node), calculated under base case conditions. Abbreviations: CP, current practice algorithm; DALY, disability-adjusted life-year; DS, drug-susceptible; Dx, diagnosis; HIV, human immunodeficiency virus; MDR, multidrug-resistant; PLHIV, people living with HIV; SSX, symptom screen/Xpert algorithm; RIF, rifampin resistance; TB, tuberculosis.

Figure 2.

Ranges of incremental cost-effectiveness ratio (US$ per disability-adjusted life-year averted) of a World Health Organization–recommended tuberculosis diagnostic algorithm vs current recommended practice at Ethiopian HIV clinics. ^aGraph truncated for space reasons; in this case, ICER = $1995. ^bUnder these conditions, the symptom screen/Xpert algorithm was cost-saving; ICERs are not reported in these cases. ^cUnder these conditions, the symptom screen/Xpert algorithm was less effective than current practice; the ICER was not reported in this case. ^dAt low Xpert sensitivity of 66% [10], the symptom screen/Xpert algorithm was dominated (more costly and less effective) at current practice; the ICER was not reported in this case. Abbreviations: AFB, acid-fast bacillus; DALY, disability-adjusted life-year; DS, drug-susceptible; DST, drug susceptibility testing; HIV, human immunodeficiency virus; ICER, incremental cost-effectiveness ratio; IPT, isoniazid preventive therapy; MDR, multidrug-resistant; TB, tuberculosis; WHO, World Health Organization.