COST-EFFECTIVENESS OF ALTERNATIVE DIAGNOSTIC MODALITIES FOR SQUAMOUS CELL CARCINOMA OF THE CONJUNCTIVA (SCCC) AMONG HIV-INFECTED PATIENTS IN CENTRAL AND EAST AFRICA

Purpose: Nearly one in ten HIV-infected individuals experience SCCC in equatorial Africa, where SCCC incidence has increased >10-fold since the onset of the HIV epidemic despite antiretroviral therapy (ART) scale-up. We examined the incremental costs, health outcomes, and cost-effectiveness of alternative SCCC diagnostic modalities for HIV-infected persons with ophthalmic symptoms in Central and East Africa.

Method: We used a decision analytic model to compare six SCCC diagnostic modalities for HIV-infected adults on ART and presenting with ophthalmic symptoms in a hospital clinic. Diagnostic strategies were: Clinical Exam with Slit Lamp (standard of care), In-vivo Staining with Toluidine Blue Dye, Impression Cytology, In-vivo Confocal Microscopy, Anterior Segment Optical CT, and Excision Biopsy. In the model, diagnosed SCCC is treated via excision biopsy (early SCCC) and eye amputation and chemotherapy (advanced SCCC). Region-specific, conservative estimates for SCCC prevalence among HIV-infected persons with ophthalmic symptoms, test characteristics, and SCCC disease progression, including mortality risk, come from the literature. Health outcomes are disability-adjusted life years (DALYs) based on life expectancy of 35-year-old HIV-infected individuals receiving ART in Uganda and published disability weights for moderate and severe vision loss, blindness, and chemotherapy. For SCCC diagnostic testing, we include direct labor, equipment, and material costs based on market prices; annual costs of ART and other routine HIV management reflect negotiated reference prices. Incremental cost-effectiveness ratios are in 2010 US$/DALY averted using a modified societal perspective and 3% annual discount rate. Cost-effectiveness thresholds are 3x GDP/capita for WHO's AFRO E region (3x $1,413).

Result: Per patient SCCC diagnostic costs range from $16.56 (Slit Lamp) to $103.33 (Biopsy). Compared to no screening and treatment, Optical CT increases expected costs by $45 and averts 0.22 DALYs per patient, or $210/DALY averted. Biopsy cost an additional $65 and averts 0.004 more DALYs, or $14,640/DALY averted. Remaining strategies were eliminated due to weak (Impression Cytology) or strong dominance (Slit Lamp, Dye, Microscopy). Results are sensitive to SCCC disease prevalence and mortality risk associated with advanced disease (Figure 1), as well as the false positive rate of Optical CT.

Conclusion: Optical CT is cost-effective for SCCC diagnosis in HIV patients with ophthalmic symptoms. As HIV-infected individuals live longer and SCCC disease burden rises, low-cost and routinely available diagnostics will be critical for early SCCC detection.