This study of the cost of HIV testing in different scenarios was based on updated cost estimates for EIAs and rapid tests, which have increased considerably since earlier analyses.11,12
The second outcome measure, cost per HIV-infected patient correctly notified of his/her test results in various scenarios, is of policy interest to practitioners in STD clinics and emergency rooms around the country.
The costs of HIV screening depended on differences in testing technologies, counseling approaches, and HIV prevalence in the patient population. The complete rapid testing procedure was more expensive than conventional testing because of higher test kit costs and the additional counseling required for HIV-infected patients during both the first and second visits. However, when test acceptance and return rates in the different scenarios were taken into account, the expected cost of correctly notifying an HIV-infected patient of his/her results was consistently lower with the rapid test procedure than with conventional testing.
Of the three scenarios examined, the CT procedure in STD clinics was the most costly approach for notifying HIV-infected patients of their test results. The per-patient costs of receiving test results with screening in STD clinics with either rapid or conventional tests were lower than those of the CT procedure, given the reduced counseling costs and higher test acceptance rates associated with screening.
The cost per infected patient receiving test results for the rapid test in the ED Screening scenario ($1,638) was the lowest for any of the settings (), demonstrating the potential utility of screening in this setting. These ratios were similar to those reported elsewhere. Walensky et al.23
reported a cost of $4,850 per positive test result for routine screening at urgent care centers in Massachusetts. Golden et al.24
cited costs per new case of HIV identified ranging from $3,120 in prisons to $56,000 for testing a general U.S. population, with most estimates varying between $3,500 and $6,500.
Although the per-patient costs of receiving test results were lower for rapid testing than for conventional testing in all settings, these estimates were very sensitive to the costs of the tests themselves. Only a 20% increase in the $9.00 cost of the rapid test kit in the screening settings would make the rapid test procedure testing and notification costs higher than those for the conventional procedure. Current retail costs of rapid test kits range from $8.00 to $18.00. Costs of less than $3.50 for an EIA test result would also give the cost advantage to the conventional procedure. The base case value of $4.35 was selected to represent an automated EIA procedure, but the cost per test result varied considerably with testing volume. Given volume discounts and the need to run multiple controls with each batch of specimens, large laboratories that perform EIAs with many specimens in each run report costs of less than $2.00 per test result, whereas smaller hospital laboratories, testing a mean of 12 specimens per day, report costs of more than $10.00 per EIA result. The actual charge facing a provider often differs substantially from the cost of the EIA and could be at least $10.00, which would then favor the rapid test procedure.
The model shows that rapid testing has a cost advantage when return rates for conventional test results by infected patients are low. In their analysis of HIV tests in various sites for the U.S. Preventive Services Task Force, Chou et al.25
noted that rapid testing was associated with a higher rate of knowledge of serostatus than was conventional testing. In the current analysis, if less than 55% of those who tested HIV-positive in EDs returned for conventional test results, rapid testing would have the cost advantage. Although follow-up or outreach efforts for infected patients who fail to return for their test results are often necessary with conventional testing,26,27
this study was unable to take these factors into account due to lack of relevant cost data.
The cost per HIV-infected patient receiving test results is highly dependent on HIV prevalence. These costs rise dramatically when HIV prevalence is extremely low because there are few HIV-infected patients to be identified. Coil et al.28
reported estimates of HIV prevalence among ED patients ranging from zero to 14.0%. The lower-bound estimates of 0.2% and 0.7% by Mehta et al.29
for an ED in an urban public medical center correspond to costs of approximately $8,000 at the 0.2% prevalence and $2,400 at the 0.7% prevalence in this analysis. The 5.4% prevalence observed by Kelen et al.30
would result in costs ranging from $900 to $300 per HIV-infected patient. Clearly, the characteristics of the population treated in a given ED can have a major impact on the costs of the screening procedures.
The cost results also depend on the value of providing preliminary positive rapid test results in the ED setting. If doing so is not considered useful (an outcome value of 0.00 rather than 0.99), the cost for an HIV-infected person receiving test results for the rapid test increases from the baseline value of $1,638 to $2,511 because of a large proportionate increase in testing costs with no increase in effectiveness. Although data on changes in risk behavior after receipt of a preliminary positive HIV test result are not yet available, research shows that patients who receive such results are much more likely to learn their confirmatory test results.26
Increased testing in the ED setting is likely to have a substantial effect on minority communities, given the demographics of patients seeking care in this setting. In a study of routinely offered HIV and STD screening to as many age-eligible patients as possible in an urban nonprofit hospital ED, Silva et al.13
found that patients treated during the study hours were primarily women (56.0%) and non-Hispanic black (61.7%) or Hispanic (30.8%). More than 75% of the patients were black in a study of ED testing in a Midwestern urban teaching hospital in a low-prevalence area,27
while significant majorities of black and Hispanic patients were tested in three demonstration projects in EDs in Los Angeles, New York City, and Oakland, California.14
This study, which updated the provider costs of screening for HIV infection in various settings, drew its input parameters from a substantial number of time and motion cost collection studies, meta-analyses, and CDC demonstration projects. However, the study was subject to several limitations. There may be longer-term effects of counseling and testing compared with screening that could not be included in this analysis. Counseling might affect the behavior of either infected or uninfected patients, influence their likelihood of returning for test results, or influence whether they are likely to enter into care. Meta-analyses have shown that information-based counseling increases safe behaviors and decreases risky behaviors among HIV-infected people, but there is typically a lesser or no effect among uninfected people included in these studies.31
Structured, theory-based, client-centered counseling has been shown to reduce risk behaviors and STD infections among HIV-uninfected people in an STD clinic,18
but its cost may be higher than that considered in the current analysis, and its use may result in a smaller number of patients being tested in busy ED settings.14
This study did not attempt to assign any reduction in value attributable to preliminary false-positive results. However, the meta-analysis by Hutchinson et al.10
found that preliminary false-positive results are relatively rare (0.6%) with rapid testing, so this would have little effect on this analysis conducted from the provider perspective.
This study also did not attempt to address the costs associated with follow-up of HIV-infected people who failed to return for their test results, or of facilitating entry into care following a positive HIV test. Although this is an important issue, data are sparse, cost estimates of the process vary widely, and these costs are often incurred by other institutions. Kassler et al.26
showed that 30% of patients who tested positive after conventional testing required field follow-up to notify them of their test results, compared with 3% of patients who received a preliminary positive rapid test result. By extension, people who receive immediate results from rapid tests may be more likely to engage in follow-up care than the large proportion of people who fail to receive their results after conventional testing.