Cost-Effectiveness of Voluntary HIV Testing Strategies in a Very Low-Prevalence Country, the Republic of Korea

Testing procedure

The ELISA HIV testing procedure involved phlebotomy, and submission of a serum specimen to a PHC laboratory for processing. Specimens with positive ELISA results were re-tested, and repeatedly reactive samples were subjected to confirmatory western blot analysis. If the second ELISA yielded negative results, no further analysis was performed. The examinee was notified of the results within 1 week via telephone.9

Rapid HIV testing was performed using a finger-stick kit (SD BIOLINE HIV-1/2 3.0; Standard Diagnostics, Inc., Yongin, Korea). After blood sampling via finger-stick, the test result could be read within 20 minutes. Staff informed examinees of their results in a face-to-face meeting or via telephone. Examinees with positive rapid test results were asked to submit to ELISA testing. If ELISA results were positive, confirmatory western blot analysis was performed.

Examinees confirmed to have HIV infection were referred for further counseling at a PHC.9 Both the ELISA and rapid tests were performed anonymously and free of charge.

Strategies and scenarios

In Strategy 1, ELISA testing was performed to detect HIV in all examinees. In Strategy 2, HIV detection was performed by rapid testing using a finger-stick kit. Since the examinees' risk level was unknown, analyses were performed in two different scenarios: one assuming that examinees belonged to an average-risk population, and the other assuming a high-risk population, such as men who have sex with men (MSM). In both scenarios, we determined the total cost of identifying a previously undiagnosed HIV infection in a PHC setting.

Decision tree

A decision tree model was developed to assess the cost-effectiveness of voluntary HIV testing at PHCs (Fig. 1). The decision tree structure represented both HIV testing strategies and both scenarios. Analyses were performed using TreeAge software (TreeAge Software Inc., Williamstown, MA, USA). For example, if a HIV-infected case underwent ELISA or rapid testing, the probability of a positive result being positive reflected the sensitivity, and the probability of it being negative would be 1 − sensitivity. Meanwhile, if a non-infected case underwent ELISA or rapid testing, the probability of the test result being negative would reflect the specificity, while the probability of it being positive would be 1 − specificity.

Fig. 1
Summary of HIV testing protocols.
HIV = human immunodeficiency virus, ELISA = enzyme-linked immunosorbent assays.

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Input variables

Table 1 shows the input variables for each procedure. The listed baseline probabilities for estimating the cost per identified HIV-infected case using the two testing methods correspond to the chance nodes in Fig. 1. The HIV prevalence among the average-risk population in Korea was obtained from a UNAIDS report.10 The HIV prevalence among the high-risk population was acquired from a study of HIV infection global epidemiology among MSM in the Asia-Pacific region.11 Since there are no domestic reports on this subject, we assumed the test acceptance rate suggested by Farnham et al.12 The utilized sensitivities and specificities of the ELISA, western blot, and rapid test, and the acceptance rate for the confirmatory test after the reactive rapid test, were found in the literature.13, 14, 15

Table 1
Summary of input parameters for the HIV testing cost-effectiveness analysis

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Our analysis included only additional costs. Fixed costs, such as wages, were not considered because the examinees' choice of ELISA or rapid testing did not influence the monthly pay of the PHC staffs, or the number of laboratory technicians required. Costs were estimated from the provider perspective. All costs were reported in 2017 US dollars, assuming an exchange rate of KRW 1,000 for USD 1. The cost data for each HIV testing procedure—including the price of reagents, test kits, and laboratory supplies—were obtained from estimates provided by the test kit manufacturers and from the laboratory staff of the Seoul Research Institute of Public Health and Environment.

Outcome measures

Outcome measures were the average per-patient cost of completing the entire ELISA or rapid testing procedure, and the additional cost per identified and previously undiagnosed HIV-infected case. The latter was the key measure of cost-effectiveness, and was calculated by dividing the former average cost by the HIV infection detection rate per examinee. The detection rate was the product of HIV prevalence, the testing tool sensitivities, and the test acceptance rate.

Sensitivity analysis

Sensitivity analysis was performed using the input probabilities and cost variables that affected the cost per identified HIV-infected case. The HIV prevalence ranged 0.00024–0.0004 in the average-risk population, and 0.049–0.056 in the high-risk population. The acceptance rate for the ELISA and rapid test ranged 0.67–1.0, and the acceptance rate for western blot analysis after a reactive rapid test ranged 0.5–1.0. Test costs ranged from USD 3.5 to USD 5.0 for the ELISA, from USD 1.8 to USD 2.5 for the rapid test, and from USD 77.0 to USD 110.0 for the western blot kits.

Ethics statement

The present study protocol was reviewed and approved by Institutional Review Board (IRB) of Seoul National University (IRB No. E-1608-113-786).

Average cost of the HIV testing procedure

Table 2 summarizes the average costs per examinee completing the conventional ELISA and rapid test procedures. The average costs were higher for HIV-infected examinees than for uninfected examinees, since a positive result required confirmation with a second ELISA and western blot analysis. The overall average costs were consistently lower for the rapid testing procedure compared to ELISA because the rapid test kit was cheaper than the ELISA kit. The average per-examinee cost was USD 3.38 for ELISA and USD 1.61 for rapid testing in scenario 1 (average-risk population), and USD 7.62 for ELISA and USD 4.77 for rapid testing in scenario 2 (high-risk population).

Table 2
Average cost per examinee for HIV testing strategies^a

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Cost-effectiveness of HIV testing strategies

Table 3 presents data regarding the additional cost per newly identified HIV patient among all examinees, as well as the cost-effectiveness of the two scenarios. In scenario 1, the additional cost was USD 42,237 with ELISA and USD 26,974 with the rapid test. In scenario 2, the additional costs were USD 183 and USD 153, respectively.

Table 3
Cost-effectiveness of HIV testing strategies^a

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Sensitivity analysis

In scenario 1, the cost of the rapid test kit was the variable having the largest effect on the average cost per identified HIV-infected individual. One-way sensitivity analysis revealed that the rapid test's cost-effectiveness was best at USD 24,292, with the lowest-priced rapid test (USD 1.80), and worst at USD 33,682, with the highest-priced rapid test (USD 2.50). On the other hand, the cost-effectiveness of the ELISA was consistently USD 42,237.

In scenario 2, the acceptance rate of ELISA testing after a reactive rapid test was the variable with the largest effect on cost-effectiveness. One-way sensitivity analysis revealed that the rapid test's cost-effectiveness was best at USD 141 with the highest ELISA acceptance rate (100%), and worst at USD 179 with the lowest ELISA acceptance rate (50%). In contrast, the cost-effectiveness of ELISA was consistently USD 183. In both scenarios, the rapid test was more cost-effective than the ELISA.

In a setting with higher HIV prevalence, the costs would be increased for both strategies in both scenarios. However, the cost-effectiveness for detecting previously undiagnosed HIV cases would be improved due to the lower the additional cost per HIV patient detected. Likewise, in a lower prevalence setting, the cost-effectiveness would be decreased.

All sensitivity analyses indicated that the rapid test had a consistent cost advantage over the ELISA, with regards to both the average cost per-examinee and the additional cost per identified HIV-infected case.