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HIV Incidence during a Cluster-Randomized Trial of Two Strategies Providing Voluntary Counselling and Testing at the Workplace, Zimbabwe
Global Health Sciences Literature Digest
Published March 26, 2007
Journal Article

Corbett EL, Makamure B, Cheung YB, Dauya E, Matambo R, Bandason T, Munyati SS, Mason PR, Butterworth AE, Hayes RJ. HIV Incidence during a Cluster-Randomized Trial of Two Strategies Providing Voluntary Counselling and Testing at the Workplace, Zimbabwe. AIDS. 2007 Feb 19;21(4):483-9.


To determine whether delivery of two voluntary counseling and testing (VCT) strategies to HIV-negative employees affects HIV incidence.

Study Design

This study is a secondary, retrospective analysis of a parent study that was designed to determine VCT uptake in the setting of intensive versus standard strategies. Business occupational health clinics were randomized by cluster to the two different VCT strategies, and VCT uptake was found to be 51.1% in the intensive arm and 19.2% in the standard arm.


This study took place in 22 small- and medium-sized businesses in Harare, Zimbabwe. As described in the parent study, the businesses were identified with the assistance of the Zimbabwe AIDS Prevention Project and were eligible to participate if they had 1) 100 to 600 employees; 2) an occupational or first aid clinic; and 3) individual-based absenteeism records. Payrolls were used to identify all employees and were re-examined every three months for new employees and loss of employment.


Participants were 3,146 individuals who had initially tested HIV-negative and remained in employment at the end of the intervention. Of these individuals, 2,966 (1,463 in the standard VCT arm, and 1,503 in the intensive VCT arm) consented to repeat HIV testing for this study. There were no significant differences in the baseline characteristics of the randomization arms. Participants were predominantly male (88.4% in the standard VCT arm and 90.5% in the intensive VCT arm) and married (75.4% in the standard VCT arm and 76.3% in the intensive VCT arm). The average age was 36.7 years in the standard arm and 33.3 years in the intensive arm.


Twenty-two businesses were recruited, categorized into three strata according to absenteeism rates, and randomly allocated to either intensive or standard VCT, with randomization stratified by absenteeism category. All employees expected to remain employed for at least three months were invited for interview and offered VCT according to the allocated strategy. Intensive VCT was modeled on UNAIDS recommendations, except that couple counseling and testing was not possible unless both partners were employed by the same company. Participants had pre-test counseling, risk assessment, HIV testing and results, and post-test counseling with risk-reduction planning on the same day. Follow-up counseling and repeat VCT were available. Participants at businesses randomized to standard VCT had pre-test counseling and risk assessment and were then given a pre-paid voucher to a chain of free-standing VCT providers using similar counseling and testing methods. A two-week appointment was given to discuss the employees' results and risk-reduction plans. Employees who had not used their vouchers after two weeks were actively followed up and given up to two further reminders and follow-up appointments before being considered not to have completed VCT. VCT was linked to the same package of basic workplace HIV care provided for two years at each business, with the intervention finishing in July 2004. Free condoms were available throughout the intervention. New employees were enrolled and offered VCT. Counseling was conducted by experienced nurse-counselors who underwent in-house training and used a standardized approach. A supervisor periodically observed sessions and conducted exit interviews. Debriefing meetings and refresher trainings were held every two weeks and six months, respectively.

Primary Outcomes

The primary outcome was HIV incidence rates for participants in both study arms. Rapid HIV testing was performed anonymously on-site using blood (78%) or oral (22%) specimens. All positive tests were confirmed with repeat testing.


Of the initially HIV-negative employees in the standard and intensive VCT arms, 95.4% and 93.2% respectively were still in employment and consented to anonymous HIV testing at the end of the intervention. Loss to follow-up before the second HIV test was 30.3% in the standard VCT arm and 32.2% in the intensive VCT arm. Mean VCT uptake during the previous two years was 70.7% in the intensive arm and 5.2% in the standard arm (p<0.001). In the standard VCT arm, 17.1% of participants accepted pre-test counseling and a voucher, but did not complete testing.

Sixty-one sero-converters were identified during 5,022 person-years follow-up (PYFU; crude HIV incidence 1.21 per 100 PYFU; 95% CI: 0.92–1.64). HIV incidence was higher in the intensive VCT arm (mean per-site HIV incidence 1.37 per 100 PYFU) than in the standard VCT arm (mean per-site HIV incidence 0.95 per 100 PYFU), but the difference was not significant (unadjusted relative risk 1.44; 95% CI: 0.77–2.71). Multivariate adjustment for potential confounders did not substantially affect the results, with the adjusted relative risk for sero-conversion being 1.49 (95% CI: 0.79–2.80) for intensive compared to standard VCT provision. Repeating the analysis after excluding the site with the highest HIV incidence in each arm (removing the potential outlier from the intensive VCT arm) reduced the difference between arms to an unadjusted rate ratio of 1.30 (95% CI: 0.75–2.22) and an adjusted rate ratio of 1.28 (95% CI: 0.76–2.19). On univariate analysis the sero-conversion rates varied significantly by marital status, and multivariate analysis significantly associated age less than 25 years (incidence rate ratio compared to 35 to 44 year olds, 2.71; 95% CI; 1.23–5.94) and being widowed (incidence rate ratio 7.59; 95% CI: 2.34–24.65) with sero-conversion.


The authors conclude that highly acceptable VCT did not reduce HIV incidence in this predominantly male cohort, and careful comparison of outcomes under different counseling and testing strategies is still needed to maximize HIV prevention from global scale-up of VCT.

Quality Rating

Based on the Jadad criteria, this study received a high quality rating. The process of randomization was adequate and described, and there was a description of drop-outs. Due to the nature of the intervention, blinding was not a factor. One considerable limitation to this study is the loss to follow-up rate of over 30% in each arm, which could significantly bias the results. Additionally, this study was not designed to assess HIV incidence. The conclusions drawn from these relatively low HIV incidence rates may therefore be misleading, despite their statistical significance.

In Context

This study is the first randomized trial to report HIV incidence under different VCT strategies in Africa. It showed no significant difference in HIV incidence among employees who initially tested negative under two randomly allocated, workplace-based VCT strategies, despite a major difference in acceptability.(1) These findings are in agreement with other studies, mostly from the United States, indicating that HIV testing has little effect on risk-taking or incidence of sexually transmitted infections among individual HIV-negative clients.(2,3) Rather, behavior change following knowledge of sero-status has been found among HIV-infected individuals and in discordant couples. (4,5)

Programmatic Implications

The acceptability and behavioral impact of VCT are distinct outcomes for HIV-negative clients that may vary independently under different approaches to providing VCT. Although the contribution from VCT towards HIV prevention comes primarily from identification of HIV-infected clients, the majority of clients in most locations will be HIV-negative. Research is needed to inform and maximize the benefits and minimize any potential harm from VCT before large global scale-up is implemented.


  1. Corbett EL, Dauya E, Matambo R, Cheung YB, Makamure B, Bassett MT, et al. Uptake of workplace HIV counselling and testing: a cluster-randomised trial in Zimbabwe. PLoS Med 2006 Jul;3(7):e238.
  2. Matambo R, Dauya E, Mutswanga J, Makanza E, Chandiwana S, Mason PR, et al. Voluntary counseling and testing by nurse counselors: what is the role of routine repeated testing after a negative result? Clin Infect Dis 2006 Feb 15;42(4):569-71.
  3. Weinhardt LS, Carey MP, Johnson BT, Bickham NL. Effects of HIV counseling and testing on sexual risk behavior: a meta-analytic review of published research, 1985-1997. Am J Public Health 1999 Sep;89(9):1397-405.
  4. DeCock KM, Marum EL, Mbori-Ngacha D. A serostatus-based approach to HIV/AIDS prevention and care in Africa. Lancet 2003 Nov 29;362(9398):1847-9. (No abstract available.)
  5. The Voluntary HIV-1 Counseling and Testing Efficacy Study Group. Efficacy of voluntary HIV-1 counseling and testing in individuals and couples in Kenya, Tanzania, and Trinidad: a randomized trial. The Voluntary HIV-1 Counseling and Testing Efficacy Study Group. Lancet 2000 Jul 8;356(9224):103-12.