The primary purpose of HIV testing is to diagnose previously unidentified HIV-infected individuals. Currently in the United States, the algorithm used to diagnose HIV infection includes an Enzyme Linked Immunosorbent Assay [ELISA] followed by confirmatory Western blot [WB] testing. Although a positive HIV serology does not serorevert to negative, HIV-infected persons often undergo additional confirmatory testing following their initial diagnosis. Likely reasons for repeat testing following a positive WB test result include as a requirement for enrollment in Ryan White programs or inaccessibility of previous laboratory results when an individual presents for medical care. Because of limited resources additional confirmatory testing after the first positive WB should be kept to a minimum to reduce unnecessary costs.

In 2006, the Centers for Disease Control and Prevention [CDC] published revised recommendations for routine HIV testing in health-care settings [1]. An unintended consequence of expanded screening will likely be an increase in the amount of repeat HIV WB testing when newly diagnosed individuals are referred for medical care from sites that do not typically provide specialty care, such as emergency departments or community-based organizations. For example, following implementation of expanded screening in New York City, approximately 63% of persons testing positive by WB between 2004 and 2006 had previously been diagnosed with HIV infection [2]. This repeat WB testing was therefore not necessary and understanding the full reasons why this occurs could help reduce its frequency and the associated costs.

There is no literature discussing the role of repeat positive confirmatory HIV testing and its relationship to patient care. However, the rationale for repeating a serologic test that does not revert to seronegative over time must be measured by its effect on linkage to and retention in HIV care. The objectives of this investigation were [A] to quantify the frequency of repeat positive confirmatory testing, and [B] to describe associated factors, including those related to healthcare utilization.

Between January 1, 1997, and December 31, 2008, there were 12,504 study-eligible HIV-infected SC residents reported to eHARS of 20% progressed to AIDS >1 year following HIV diagnosis (Table 1). The overall median age at diagnosis was 36 years, and most diagnoses were among males. The greatest proportion of new diagnoses occurred among non-Hispanic blacks. The most common reported HIV risk categories were heterosexual contact and male-male sex

There were 7,071 [57%] individuals with at least one additional positive WB reported at some date after initial diagnosis. After classifying all confirmatory tests based on time since initial HIV diagnosis, 8,193/12,504 [65.5%] persons did not have an additional positive WB ≥90 days after diagnosis and 4,311 [34.5%] had repeat confirmatory tests ≥90 days following their first positive HIV test date. eHARS captured 7,570 separate positive WB test results among the individuals who had repeat confirmatory testing following initial diagnosis, resulting in a median of 3 [range: 2-14] positive WB results for these persons. The median interval between first positive WB and any additional confirmatory test following diagnosis was 913 [range: 91-4,658] days. Most of the repeat testing [55%] occurred within three years of an initial HIV diagnosis. Individuals diagnosed from 2000 through 2008 had the majority of their repeat WB tests occurring within three years, but individuals diagnosed prior to 2000 had the majority occurring greater than three years after diagnosis. Individuals diagnosed with HIV between 1997 and 2000 accounted for the majority of repeat tests [54%], indicating that individuals with a longer follow-up period contributed a greater number of repeat WB tests, with the total number of repeat WB tests increasing significantly with earlier years of HIV diagnosis [p<0.0001]. This was further demonstrated by examining year of HIV diagnosis by repeat tester status. For individuals diagnosed between 1997 and 2001, approximately 40% were repeat testers; between 2002 and 2005, approximately 32% had any repeat WB test; for 2006 and 2007, 21% had repeat WB tests; and only 12% had repeat tests when diagnosed in 2008. Finally, the median initial CD4+ T-cell count was 240 [range: 0-2,562] cells/µL for persons with repeat positive WB compared with 196 [range: 0-1,970] cells/µL for persons without repeat positive WB results [p < 0.0001].

On multivariable analysis, race/ethnicity, risk category, age, disease stage, and source of report were found to be independently associated with repeat confirmatory testing following diagnosis (Table 2). Specifically, non-Hispanic blacks were more likely to have repeat testing compared with non-Hispanic whites. Individuals with all other risk categories were more likely to have repeat testing compared with male-to-male sexual contact. Individuals in all age categories ≥25 years were less likely to have repeat testing compared to individuals aged 18-19 years. Those with an intermediate diagnosis of HIV were more likely to have repeat confirmatory testing compared to those with an early diagnosis. Finally, those who received an initial HIV diagnosis at a group practice/private medical doctor, hospital, or federal facility were less likely to have repeat confirmatory testing, while those diagnosed at a SC state facility, another state, or other type of facility were more likely to have repeat confirmatory testing compared with individuals diagnosed at county health department facilities.

In the subset of 8,677 individuals included in the analysis of engagement in care, the proportion of persons who had either a CD4+ T-cell count or viral load reported to eHARS in the 6-month intervals ranged from 49.7% to 53.2% (Table 3). An assessment of the level of care engagement shows that 2,564 [30%] were consistently in care, 3,491 [40%] had sporadic care, and 2,622 [30%] were not in care. Persons who had repeat confirmatory tests after diagnosis were more likely than those who had a single confirmatory test to be consistently engaged in care or have sporadic care during 2007-2009. The frequency of positive WB test results differed by care status: more than one WB test result was reported for 68% of those individuals in sporadic care, 63% of those consistently in care, and 54% of those individuals not in care [p<0.0001].

More than one-third of individuals included in this analysis had repeat WB confirmatory testing after initial diagnosis. We identified a number of factors that were independently associated with having repeat confirmatory HIV testing, including non-Hispanic black race; reported HIV risk category; younger age; intermediate stage of infection at diagnosis; source of report of initial HIV diagnosis; and sporadic care. However, it is an important surveillance principle that repeat diagnoses are reported each time they occur in order to promote greater completeness for incidence/prevalence of a disease. But HIV serology does not revert to negative and so reducing volume of and need for repeat testing should be a public health goal. Because WB testing is complex, expensive and time-consuming, the occurrence of multiple positive confirmatory WB testing for individuals suggests delayed linkage and poor retention in care and this may impact health outcomes.

For non-Hispanic blacks compared with non-Hispanic whites, possible reasons for repeat confirmatory testing may be that relatively few non-Hispanic blacks had primary care providers, and those who did had low continuity of care with these providers and accessed care from multiple sites as needed [9, 10]. If medical records are not accessible at the time that care is sought [thus lack of accurate information about testing sites, frequent name and address changes, multiple insurance/medical chart numbers, etc], a WB test may be repeated to confirm diagnosis before HIV medical care is initiated. In addition, African Americans might be more likely than persons from other racial/ethnic groups to get most of their care in urgent care/emergency department settings, [11, 12] and they also may be more likely than others to lack confidence in the initial diagnosis and therefore seek reconfirmation of the diagnosis [13].

Young age is associated with reduced likelihood of returning for test results [14] and being more likely to have unstable living situations [15-18]. These associations will reduce the chances that a young individual will learn the results of HIV testing from providers or public health personnel. Also, younger individuals are less likely than older persons to have health insurance or a primary care provider [19]. Lack of health insurance may result in the use of multiple facilities for healthcare, leading to repeat WB testing when previous HIV test results cannot be easily verified.

There was considerable variability in the association of repeat positive confirmatory testing with facility source of initial HIV diagnosis. Individuals were more likely to have repeat positive WB results if they were initially diagnosed in another state, in a state facility [e.g., prisons] or if the source of initial testing was other [e.g., blood bank, insurance purposes], suggesting that one reason for additional testing is to confirm and/or document serostatus as part of engagement or reengagement in care. In SC state facilities [e.g., prisons, Department of Mental Health], individuals are tested on entry and treatment for HIV infection is located within the same facility. Our data do not allow us to determine the pattern of testing on release from prisons or mental health facilities. However, other studies and reports suggest that benefits and continuity of care are frequently not achieved following release, [20-22] and this may lead to increased repeat testing in the community as persons transfer or later re-engage into care, as demonstrated by our data. Better communication between diagnosing and treatment facilities and developing Memorandums of Understanding would serve to reduce delays in confirming infection and initiating care.

Sporadic care may be associated with additional HIV tests being performed when individuals return to medical care or do not disclose their serostatus when HIV testing is offered. Failure to remain in care suggests absence of or inconsistent use of antiretroviral therapy, which might explain why persons who had repeat testing were more likely to progress to AIDS >1 year following initial HIV diagnosis. In contrast, progression to AIDS within a year was likely not associated with repeat confirmatory testing because severely immuno-compromised and ill individuals remain engaged in care after linkage and this decreases opportunity for repeat testing. Failure to link and retain persons to care following initial diagnosis is a missed opportunity to allow access to life-saving antiretroviral medications. Use of case management, such as the brief enhanced case management model developed by the Antiretroviral Treatment Access Study [ARTAS], may be one way to link patients quickly and effectively to care after diagnosis, [23, 24] and future studies should identify approaches to increase retention in care [25-30].

Another important reason for repeat testing could be transfer of care to other facilities. Repeat HIV testing is conducted routinely for a new patient during initial patient visits [31]. We found that persons who had evidence of uninterrupted care were more likely to have multiple positive WB results than those not in care and hypothesize that many of these persons had repeat testing upon transfer of care. However, persons who had repeat positive WB results were almost twice as likely to have an intermediate AIDS diagnosis, and it is unlikely that persons diagnosed later in the course of HIV infection derive much benefit from additional HIV testing.

An implication of this analysis for minorities, younger individuals, and those diagnosed later during the course of HIV infection is that having a primary care provider and stability of medical care are key issues related to repeat confirmatory HIV testing and clinical outcomes. Finding ways to promote access to and use of primary care providers and increased stability of care, regardless of the type of insurance a person has, will be important, and healthcare reform may facilitate this.

This analysis has several limitations. First, we used population-level surveillance data which did not include information on knowledge, attitudes and beliefs of individuals. Second, the data do not allow the determination of whether repeat positive WB results were due to initiation of testing by patients or by providers. Because of this, the exact reason[s] for repeat testing cannot be described. Third, surveillance data do not allow determination of the setting in which repeat testing is conducted [e.g., outpatient clinic versus inpatient unit], by the source of report or the type of provider who ordered the testing [e.g., infectious disease specialist, primary care provider, emergency department provider, or other provider]. Fourth, although reporting of WB test results is done by all SC licensed laboratories and is required by law, the completeness of reporting of WB testing by laboratories in SC has not been evaluated. However, reporting bias by laboratories is likely to be minimal as they all report results to the SC surveillance system electronically. Fifth, it is possible that there was some out-migration of our HIV-infected population that occurred during our follow-up period. Some individuals included in the analysis as not in care or sporadic care may have moved out of state prior to any repeat WB testing or engagement in care. This is a limitation inherent in surveillance data. Sixth, the care status demonstrated from 2007-2009 might not reflect the care status over the period assessed for repeat WB testing. If WB retesting and unstable sources of care were definitively linked, one might expect that the "sporadic care" group relative to the "in care" group would have even greater repeat level of repeat testing than is demonstrated. However, although the timing of the repeat testing relative to the assessment of care status may be separated by many years recent evaluation of care engagement shows that many individuals are not retained after repeat testing.

Finally, there are differential follow-up times for all individuals included in the study. Individuals diagnosed earlier have been followed for more years and have a greater chance of having, and actually do have more, repeat WB tests. We recognize this as a limitation, but we did not wish to exclude any data from this analysis in order for each individual to have the same follow-up period. However, adjustments to the follow-up time were made for certain analyses. We followed all individuals in the study for at least one year post-HIV diagnosis to allow for correct classification of late diagnoses, and we limited our care engagement analysis to only those individuals diagnosed prior to and still alive at the end of the period of interest. Further, varying follow-up times in our study population does not change our conclusions in any way. This data demonstrates that repeat WB tests among known HIV-positive individuals are a problem in our state, regardless of the year of diagnosis and follow-up time.

Our findings suggest that implementing interactive electronic health records in all healthcare systems and finding ways to facilitate sharing of data between systems, while protecting patient confidentiality, might reduce unnecessary repeat testing. One benefit would be to foster timely access to laboratory results by patients and providers, and this may be cost-effective [32] because less time and resources would be used conducting duplicate testing.

The traditional way to confirm [or reconfirm] HIV serostatus with WB testing and many of the likely reasons for repeat testing >90 days may not be an effective use of resources because patients are not promptly linked and retained in care soon after diagnosis. More emphasis should be placed on finding a simpler testing algorithm and facilitating early linkage and retention in care. Reconfirming serostatus at multiple encounters may satisfy requirements for enrollment and maintenance in Ryan White medication programs, but it may lead to delays in initiation of antiretroviral therapy.

More intensive post-test counseling and enhanced case management that facilitates prompt linkage into HIV care may reduce the amount of repeat positive confirmatory HIV testing that is conducted [23, 24]. However, given expected limitations in resources available for HIV diagnosis and care in the future, it is important that healthcare reform policy and clinical recommendations promote improvements in communications about previous test results that have been conducted and/or the use of easier, faster, and cheaper methods to confirm HIV infection. Easier access to medical records and interactive health information technology could be used to inform providers or prompt them to find previously completed HIV test results. However, unless providers have interactive health information technology, this notification will be limited and many providers will continue to reconfirm past diagnoses.