After testing, a temporary laboratory data file containing ID’s, specimen numbers (public keys), and HIV results was imported into the study database and linked to participants’ pseudo-IDs (Fig. 4). At the same time, each participant’s public key (specimen number) encrypted his ID, name, and HIV result into a single data packet identified by the specimen number. All encrypted data packets were then downloaded to the HIV counselors’ handheld computers, which were returned to the research office at least once a week.
Survey participants who wished to know their HIV results visited a counseling center with the counseling slip containing their public and private keys. The participant or counselor entered the public key into the handheld computer (Fig. 5). This retrieved his encrypted data and produced a message ‘HIV result available. Enter private key’. Entering the private key then decrypted the ID, name, and date of birth, which then appeared on the screen. The counselor then verified the participant’s identity through his date of birth or identity documents and provided full preresult HIV counseling. If the participant chose to proceed, the HIV result was revealed on the next screen for the client and counselor to see. The counselor then provided appropriate postresult counseling and took blood for a confirmatory HIV test on all positives. HIV results could never be accessed without a private key and anyone who lost their counseling slip had to have a repeat HIV test.
Eleven thousand five hundred and fifty-one out of 19,867 eligible residents contacted (58.1%), agreed to HIV testing. In only 9 cases (0.08%) was it impossible to link an HIV result with an individual’s epidemiologic data. All 9 cases resulted from errors in manual data capture of specimen numbers during a short period when a barcode scanner was out of order. The turnaround time between testing and availability of results at counseling centers was 2 to 3 weeks. Despite the operational success of the system, the proportion of survey participants returning for their HIV results was disappointing. Only 325 of 6859 (4.7%) women and 221 of 4692 (4.7%) men tested returned for their results.
A further 146 individuals who were not eligible for the survey requested and received VCT at counseling centers using the same system. These individuals were outside the age range for the HIV survey or were not resident in the study area.
The HIV prevalence was higher among survey participants who returned for their results than among those who did not: 29.9% of women and 22.6% of men who received their results were HIV infected compared to 26.7% of women (P = 0.01) and 13.1% of men (P <0.001) who did not. This may be partly explained by the fact that participants who returned for their results were older than those who did not: 32.6 versus 28.7 years for women (P <0.0001) and 33.3 versus 26.1 years for men (P <0.0001).
Although the proportion of participants who received their results was low, the 546 individuals who learned their HIV status during the survey may not have done so if we had used conventional linked or unlinked anonymous HIV testing with referral for parallel VCT.
Although not formally evaluated, we have no evidence that LATPCR increased survey refusal rates. The refusal rate (42%) was virtually identical to that for KwaZulu-Natal in a 2005 national linked, anonymous HIV survey (41%).24 All the national South African HIV surveys to date have had very low participation rates by international standards.24–28
Pretest HIV counseling in surveys is problematic because it requires privacy as well as substantial staff training, experience, and time7,29 – at least some of which will be spent counseling individuals who have no intention of accessing their results. Pretest counseling may also reduce survey participation as it ‘makes individual’s risks visible’.30 Conversely, anonymous HIV testing attracts more high-risk individuals.31–34 LATPCR combined the advantages of anonymous and confidential HIV testing without the need for pretest counseling in the field. It further allowed pre and postresult HIV counseling to be done by the same counselor as recommended in best practice guidelines.7 This is usually impractical in population-based HIV surveys.
Other approaches have been used to allow survey participants to access their HIV results. In ‘LAT with provision of test results’ participants receive a code which links them to their results. This is similar to the ‘nonname code’ model of anonymous VCT commonly used in testing facilities in the United States. However, this requires pretest counseling.1 Another model, ‘Voluntary Testing and Counseling’, which has been used in household HIV surveys in Uganda, also offers pre- and postresult counseling. However, survey participants have to indicate at the time of testing whether they want their results. Only if requested are named results printed and dispatched to the local counseling office.29,35,36
The capital outlay for the system was approximately $7500 for software development and $4000 for hardware (25 handheld computers and 2 barcode scanners at approximately $150 each). Equipment fared well over time with only 1 computer stolen early in the study. Routine management of samples and results was successfully performed by trained local people with high school qualifications only.
The handheld computers eliminated the need for printing and transporting results. Almost 12,000 HIV results were available at all 19 counseling centers in the study area allowing participants to receive results at any counseling venue of their choice. In settings with cellular telephone connections and Internet access, results’ turnaround time could be reduced by uploading encrypted HIV results onto handheld computers through cellular telephones.
Each handheld computer is password protected. If a handheld computer were stolen, it would be virtually impossible to decrypt even one individual’s ‘data packet’. The anonymous electronic log of all HIV results disclosed can be used to audit alleged breaches in confidentiality as well as for research into HIV testing behaviors. Examples would include identifying characteristics or events (e.g., the death of a household member in the 3 years preceding the survey) associated with participants’ accessing their HIV results or investigating how distance to counseling centers affects the uptake of results in rural areas. To date, we have not received any reports of breaches in confidentiality or unauthorized access to HIV results.
From a research point of view, LATPCR was cost-effective by optimizing the use of fieldwork, counseling and laboratory staff. It removed the need for separate blood draws and laboratory tests for parallel VCT as well as for printing and dissemination of thousands of results. VCT has been shown in many settings to be cost-effective.37–40 From a public health point of view, therefore, even the relatively small number of survey participants who received their HIV results added greatly to the overall cost-effectiveness of the survey.
LATPCR has potential for use in any research or program requiring the anonymous linkage of confidential data (which participants may choose to know) with clinical or epidemiologic information. Besides HIV, examples would include screening for sexually transmitted infections or genetic abnormalities.41 The system also has potential in VCT outreach where it would allow the paper-free, confidential dissemination of HIV results to hard-to-reach populations in nonfacility settings. In this large population-based HIV survey, LATPCR allowed us to successfully address a multitude of ethical, logistic, and scientific challenges.
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