Imputing HIV treatment start dates from routine laboratory data in South Africa: a validation study

Cohort profile: the South African National Health Laboratory Service (NHLS) National HIV Cohort

PURPOSE

South Africa's National Health Laboratory Service (NHLS) National HIV Cohort was established in 2015 to facilitate monitoring, evaluation and research on South Africa's National HIV Treatment Programme. In South Africa, 84.8% of people living with HIV know their HIV status; 70.7% who know their status are on ART; and 87.4% on ART are virologically suppressed.

PARTICIPANTS

The NHLS National HIV Cohort includes the laboratory data of nearly all patients receiving HIV care in the public sector since April 2004. Patients are included in the cohort if they have received a CD4 count or HIV RNA viral load (VL) test. Using an anonymised unique patient identifier that we have developed and validated to linked test results, we observe patients prospectively through their laboratory results as they receive HIV care and treatment. Patients in HIV care are seen for laboratory monitoring every 6-12 months. Data collected include age, sex, facility location and test results for CD4 counts, VLs and laboratory tests used to screen for potential treatment complications.

FINDINGS TO DATE

From April 2004 to April 2018, 63 million CD4 count and VL tests were conducted at 5483 facilities. 12.6 million unique patients had at least one CD4 count or VL, indicating they had accessed HIV care, and 7.1 million patients had a VL test indicating they had started antiretroviral therapy. The creation of NHLS National HIV Cohort has enabled longitudinal research on all lab-monitored patients in South Africa's national HIV programme, including analyses of (1) patient health at presentation; (2) care outcomes such as 'CD4 recovery', 'retention in care' and 'viral resuppression'; (3) patterns of transfer and re-entry into care; (4) facility-level variation in care outcomes; and (5) impacts of policies and guideline changes.

FUTURE PLANS

Continuous updating of the cohort, integration with available clinical data, and expansion to include tuberculosis and other lab-monitored comorbidities.

Understanding Repeat Positive HIV Testing in South Africa Under Changing Treatment Guidelines

Some people with HIV (PWH) test positive multiple times without initiating antiretroviral therapy (ART). We surveyed 496 ART-eligible PWH following routine HIV testing at three clinics in Soweto and Gugulethu, South Africa in 2014-2015. Among repeat positive testers (RPTs) in this cohort, we compared rates of treatment initiation by prior treatment eligibility and assessed psychosocial predictors of treatment initiation in logistic regression models. RPTs represented 33.8% of PWH in this cohort. Less than half of those who reported eligibility for ART on prior testing started treatment upon retesting, in contrast to two thirds of RPTs who were previously ineligible for treatment who started treatment once they learned of their eligibility. Those who reported coping through substance use were more likely to decline treatment versus those not using substances. PWH who test repeatedly represent a vulnerable population at risk for ART non-initiation who may benefit from interventions addressing individualized coping strategies.

Retrospective analysis to describe trends in first-ever prostate-specific antigen (PSA) testing for primary healthcare facilities in the Gauteng Province, South Africa, between 2006 and 2016

OBJECTIVES

The objective of our study was to use laboratory data to describe prostate-specific antigen (PSA) testing trends for primary healthcare (PHC) services from a single province. PHC is a basic package of services offered to local communities, serving as the first point of contact within the health system. These services are offered at clinics and community health centres (CHC), the latter providing additional maternity, accident and emergency services.

DESIGN

The retrospective descriptive study design was used.

METHODS

We analysed national laboratory data between 2006 and 2016 for men ≥30 years in the Gauteng Province. We used the probabilistic matching algorithm to create first-ever PSA cohort. We used the hot-deck imputation to assign missing race group values and the district health information system facility descriptors to identify PHC testing. We reported patient numbers by calendar year, age category and race group as well as descriptive statistics. We used multivariable logistic regression to assess any association for race group and age with a PSA ≥4 µg/L.

RESULTS

Between 2006 and 2016, numbers of men tested increased from 1782 to 67 025, respectively, with 186 984/239 506 (78.1%) tests were from clinics. The majority of testing was for men in the 50-59 age category (31.5%) and Black Africans (86.4%). We reported a median of 0.9 µg/L that increased with age. A PSA ≥4 µg/L was reported for 11.7% of men, increasing to 35.5% for the ≥70 age category. The logistic regression reported that the adjusted odds of having a PSA ≥4 µg/L was significantly lower for Indian/Asians, multiracials and whites than for Black Africans (p value<0.0001).

CONCLUSIONS

Our study has shown a marked increase in PSA testing from clinics and CHC suggestive of screening for prostate cancer. The approaches reported in this study can be extended for national data.

The Treatment Ambassador Program: A Highly Acceptable and Feasible Community-Based Peer Intervention for South Africans Living with HIV Who Delay or Discontinue Antiretroviral Therapy

We conducted a novel pilot randomized controlled trial of the Treatment Ambassador Program (TAP), an 8-session, peer-based, behavioral intervention for people with HIV (PWH) in South Africa not on antiretroviral therapy (ART). PWH (43 intervention, 41 controls) completed baseline, 3- and 6-month assessments. TAP was highly feasible (90% completion), with peer counselors demonstrating good intervention fidelity. Post-intervention interviews showed high acceptability of TAP and counselors, who supported autonomy, assisted with clinical navigation, and provided psychosocial support. Intention-to-treat analyses indicated increased ART initiation by 3 months in the intervention vs. control arm (12.2% [5/41] vs. 2.3% [1/43], Fisher exact p-value = 0.105; Cohen's h = 0.41). Among those previously on ART (off for > 6 months), 33.3% initiated ART by 3 months in the intervention vs. 14.3% in the control arm (Cohen's h = 0.45). Results suggest that TAP was highly acceptable and feasible among PWH not on ART.

Variation in HIV care and treatment outcomes by facility in South Africa, 2011-2015: A cohort study

BACKGROUND

Despite widespread availability of HIV treatment, patient outcomes differ across facilities. We propose and evaluate an approach to measure quality of HIV care at health facilities in South Africa's national HIV program using routine laboratory data.

METHODS AND FINDINGS

Data were extracted from South Africa's National Health Laboratory Service (NHLS) Corporate Data Warehouse. All CD4 counts, viral loads (VLs), and other laboratory tests used in HIV monitoring were linked, creating a validated patient identifier. We constructed longitudinal HIV care cascades for all patients in the national HIV program, excluding data from the Western Cape and very small facilities. We then estimated for each facility in each year (2011 to 2015) the following cascade measures identified a priori as reflecting quality of HIV care: median CD4 count among new patients; retention 12 months after presentation; 12-month retention among patients established in care; viral suppression; CD4 recovery; monitoring after an elevated VL. We used factor analysis to identify an underlying measure of quality of care, and we assessed the persistence of this quality measure over time. We then assessed spatiotemporal variation and facility and population predictors in a multivariable regression context. We analyzed data on 3,265 facilities with a median (IQR) annual size of 441 (189 to 988) lab-monitored HIV patients. Retention 12 months after presentation increased from 42% to 47% during the study period, and viral suppression increased from 66% to 79%, although there was substantial variability across facilities. We identified an underlying measure of quality of HIV care that correlated with all cascade measures except median CD4 count at presentation. Averaging across the 5 years of data, this quality score attained a reliability of 0.84. Quality was higher for clinics (versus hospitals), in rural (versus urban) areas, and for larger facilities. Quality was lower in high-poverty areas but was not independently associated with percent Black. Quality increased by 0.49 (95% CI 0.46 to 0.53) standard deviations from 2011 to 2015, and there was evidence of geospatial autocorrelation (p < 0.001). The study's limitations include an inability to fully adjust for underlying patient risk, reliance on laboratory data which do not capture all relevant domains of quality, potential for errors in record linkage, and the omission of Western Cape.

CONCLUSIONS

We observed persistent differences in HIV care and treatment outcomes across South African facilities. Targeting low-performing facilities for additional support could reduce overall burden of disease.

Impact of Viral Load Monitoring on Retention and Viral Suppression: A Regression Discontinuity Analysis of South Africa's National Laboratory Cohort

South African guidelines recommend repeat viral load testing within 6 months when human immunodeficiency virus (HIV) viral loads exceed 1,000 copies/mL. We assessed whether South African facilities follow viral load monitoring guidelines and whether guidelines improve HIV-related outcomes, using a regression discontinuity design in a national HIV cohort of 174,574 patients (2013-2015). We assessed whether patients with viral loads just above versus just below 1,000 copies/mL were more likely to receive repeat testing in 6 months, and we compared differences in clinic transfers, retention, and viral suppression. The majority (67%) of patients with viral loads of >1,000 copies/mL did not receive repeat testing within 6 months, and these patients were 8.0% (95% confidence interval (CI): 6.2, 9.7) more likely to receive repeat testing compared with ≤1,000 copies/mL. Eligibility for repeat testing (>1,000 copies/mL) was associated with greater 12-month retention (risk difference = 2.9%, 95% CI: 0.6, 5.2) and combined suppression and retention (risk difference = 5.8%, 95% CI: 3.0, 8.6). Patients with viral loads of >1,000 copies/mL who actually received repeat testing were 85.2% more likely to be both retained and virally suppressed at 12 months (95% CI: 35.9, 100.0). Viral load monitoring might improve patient outcomes, but most patients with elevated viral loads do not receive monitoring within recommended timelines.

The South African National HIV Pregnancy Cohort: evaluating continuity of care among women living with HIV

BACKGROUND

South Africa is home to more people living with HIV than any other country, including nearly one in three pregnant women attending antenatal care. Access to antiretroviral therapy (ART) has increased substantially since the start of the national ART program in 2004, with > 95% ART coverage during pregnancy and delivery, and vertical transmission of HIV greatly reduced. However, women who initiate ART during pregnancy are at heightened risk of dropping out of care, particularly after delivery, leading to the potential for viral transmission, morbidity and mortality. It is difficult to evaluate the success of policies of expanded access to ART care, and assess continuity of care, due to the lack of a national longitudinal HIV care database. Also, patient movement between unlinked facilities. For the first time on a national level, we propose to utilize routinely-collected laboratory data to develop and validate a cohort of pregnant women living with HIV in South Africa in a way that is uniquely robust to facility transfer.

METHODS

Using laboratory test data matched to facility type, we will identify entry to antenatal care to build the cohort, then describe key treatment milestones, including 1) engagement in antenatal care, 2) initiation of ART, 3) HIV viremia, and 4) continuity of HIV care in the postpartum period. Second, we will measure the effect of system-wide factors impacting continuity of care among pregnant women. We will assess policies of expanded treatment access on continuity of care using regression-discontinuity analyses. We then will assess mobility and its effect on continuity of care during and after pregnancy. Third, we will identify individual-level risk factors for loss from HIV care in order to develop targeted interventions to improve engagement in HIV care.

DISCUSSION

This work will create the world's largest national cohort of pregnant women living with HIV. This novel cohort will be a powerful tool available to policymakers, clinicians and researchers for improving our understanding of engagement in care among pregnant women in South Africa and assessing the performance of the South African national ART program in caring for pregnant women living with HIV.

TRIAL REGISTRATION

N/A (not a clinical trial).

Delays in repeat HIV viral load testing for those with elevated viral loads: a national perspective from South Africa

INTRODUCTION

In South Africa, HIV patients with an elevated viral load (VL) should receive repeat VL testing after adherence counselling. We set out to use a national HIV Cohort to describe time to repeat viral load testing across South Africa and identify predictors of time to repeat testing.

METHODS

We conducted a cohort study of prospectively collected laboratory data. HIV treatment guidelines have changed over time in South Africa, but call for repeat VL testing within six months if 400 to 1000 copies/mL and two to three months if >1000 copies/mL. We included patients with suppressed viral loads (indicating they are on ART) and a first elevated VL (>400 copies/mL) between April 2004 and December 2014. Follow-up began at first elevated VL and continued until repeat testing, loss to follow-up or December 2016. We calculated adjusted hazard ratios (aHR) using Cox proportional hazard models.

RESULTS

Of 371,648 patients with a VL > 400, 83.9% (311,790) had a repeat VL, in a median (IQR) of 7.0 (4.1 to 12.2) months. Of those with a first viral load 400 to 1000 copies/mL, 56.4% had a repeat VL within guideline recommended six months (defined as up to nine months), whereas among those >1000 copies/mL only 47.7% had a repeat viral load within guideline recommended two to three months (defined as up to six months). We found a small increase in repeat testing associated with higher VL value (aHR 1.11; 95% CI: 1.10 to 1.12 comparing >1000 vs 400 to 1000 copies/mL) and very low CD4 counts at first elevated VL (aHR 1.16; 95% CI: 1.13 to 1.19 comparing CD4 < 50 vs <500 cells/mm3 ). We also found strong variation in time to repeat VL testing by province.

CONCLUSIONS

Median time to repeat viral load testing for those with an elevated viral load was longer than guidelines recommend. Future work should identify whether delays are due to patient or provider factors.

Virological suppression and clinical management in response to viremia in South African HIV treatment program: A multicenter cohort study

BACKGROUND

Uptake of antiretroviral treatment (ART) is expanding rapidly in low- and middle-income countries (LMIC). Monitoring of virological suppression is recommended at 6 months of treatment and annually thereafter. In case of confirmed virological failure, a switch to second-line ART is indicated. There is a paucity of data on virological suppression and clinical management of patients experiencing viremia in clinical practice in LMIC. We report a large-scale multicenter assessment of virological suppression over time and management of viremia under programmatic conditions.

METHODS AND FINDINGS

Linked medical record and laboratory source data from adult patients on first-line ART at 52 South African centers between 1 January 2007 and 1 May 2018 were studied. Virological suppression, switch to second-line ART, death, and loss to follow-up were analyzed. Multistate models and Cox proportional hazard models were used to assess suppression over time and predictors of treatment outcomes. A total of 104,719 patients were included. Patients were predominantly female (67.6%). Median age was 35.7 years (interquartile range [IQR]: 29.9-43.0). In on-treatment analysis, suppression below 1,000 copies/mL was 89.0% at month 12 and 90.4% at month 72. Suppression below 50 copies/mL was 73.1% at month 12 and 77.5% at month 72. Intention-to-treat suppression was 75.0% and 64.3% below 1,000 and 50 copies/mL at month 72, respectively. Viremia occurred in 19.8% (20,766/104,719) of patients during a median follow-up of 152 (IQR: 61-265) weeks. Being male and below 35 years of age and having a CD4 count below 200 cells/μL prior to start of ART were risk factors for viremia. After detection of viremia, confirmatory testing took 29 weeks (IQR: 16-54). Viral resuppression to below 1,000 copies/mL without switch of ART occurred frequently (45.6%; 6,030/13,210) but was associated with renewed viral rebound and switch. Of patients with confirmed failure who remained in care, only 41.5% (1,872/4,510) were switched. The median time to switch was 68 weeks (IQR: 35-127), resulting in 12,325 person-years spent with a viral load above 1,000 copies/mL. Limitations of this study include potential missing data, which is in part addressed by the use of cross-matched laboratory source data, and the possibility of unmeasured confounding.

CONCLUSIONS

In this study, 90% virological suppression below the threshold of 1,000 copies/mL was observed in on-treatment analysis. However, this target was not met at the 50-copies/mL threshold or in intention-to-treat analysis. Clinical management in response to viremia was profoundly delayed, prolonging the duration of viremia and potential for transmission. Diagnostic tools to establish the cause of viremia are urgently needed to accelerate clinical decision-making.

Understanding the role of resilience resources, antiretroviral therapy initiation, and HIV-1 RNA suppression among people living with HIV in South Africa: a prospective cohort study

OBJECTIVE

Failure to initiate antiretroviral therapy (ART) and achieve virologic suppression are significant barriers to the United Nations 90-90-90 goals. Identifying resilience resources, or modifiable strength-based factors, among people living with HIV is critical for successful HIV treatment and prevention.

DESIGN

Prospective cohort study.

METHODS

From July 2014 to July 2015, 500 adults presenting for voluntary counseling and HIV testing who were diagnosed with HIV and were ART-eligible in South Africa (Soweto and Gugulethu) were enrolled and surveyed. Logistic regression models assessed resilience-related predictors of ART initiation within 6 months of voluntary counseling and HIV testing for HIV, and HIV-1 plasma RNA suppression within 9 months, adjusting for sociodemographic factors.

RESULTS

Within 6 months, 62% initiated ART, and within 9 months, 25% had evidence of an undetectable HIV-1 plasma RNA (<50 copies/ml). Participants who initiated ART relied less on social support from friends [adjusted odds ratio (aOR) 0.94, 95% confidence interval (CI): 0.89-0.99], coped using self-distraction (aOR 1.05, 95% CI: 1.00-1.10) and avoided coping through substance use (aOR 0.79, 95% CI: 0.65-0.97), as compared with participants who did not initiate ART. Those who achieved plasma RNA suppression relied more on social support from a significant other/partner (aOR 1.04, 95% CI: 1.02-1.07), used positive religious coping (aOR 1.03, 95% CI: 1.00-1.07), and were less likely to engage in denial coping (aOR 0.84, 95% CI: 0.77-0.92), compared with those who initiated ART but did not achieve plasma RNA suppression.

CONCLUSION

Interventions optimizing resilience resources and decreasing maladaptive coping strategies (e.g., substance use, denial) may present a feasible approach to maximizing ART-based HIV treatment strategies among South African people living with HIV.

Recreational ART use among individuals living with HIV/AIDS in South Africa: Examining longitudinal ART initiation and viral suppression

BACKGROUND

South Africa has the highest number of people living with HIV (PLWH) and one of the largest antiretroviral therapy (ART) programs globally. High rates of substance use comorbidity exist, including speculation of recreational ART use (i.e., mixing ART with other illicit drugs). Recreational ART use may affect viral load among PLWH due to ART nonadherence and/or viral resistance; however, prior quantitative research has not examined rates of recreational ART use, nor associations with HIV treatment outcomes longitudinally.

METHODS

Data were drawn from a prospective, observational cohort study (n = 500) of ART-eligible adults recruited from two HIV voluntary counseling and testing centers in Cape Town, and Johannesburg, South Africa. Multiple logistic regression models assessed recreational ART use as a predictor of ART initiation over six months and viral load suppression over nine months, above and beyond other substance use (binge drinking and illicit drug use).

RESULTS

Approximately 5% (n = 24) reported recreational ART use, which was less frequent in Cape Town compared to Johannesburg (AOR = 0.025; 95%CI: 0.003-0.19; p < 0.001). Recreational ART use was not significantly associated with ART initiation or viral suppression. Other substance use, but not recreational ART use, was significantly associated with lower odds of ART initiation (AOR = 0.54; 95%CI: 0.33-0.87; p = .01) and viral suppression (AOR = 0.47; 95%CI: 0.25-0.89; p = .02).

CONCLUSIONS

Recreational ART use was infrequent and not uniquely associated with ART initiation or viral suppression. Findings suggest that comorbid use of other substances is ultimately what may make recreational ART use problematic for ongoing engagement in care and viral suppression.

ART adherence and viral suppression are high among most non-pregnant individuals with early-stage, asymptomatic HIV infection: an observational study from Uganda and South Africa

INTRODUCTION

The success of universal antiretroviral therapy (ART) access and aspirations for an AIDS-free generation depend on high adherence in individuals initiating ART during early-stage HIV infection; however, adherence may be difficult in the absence of illness and associated support.

METHODS

From March 2015 to October 2017, we prospectively observed three groups initiating ART in routine care in Uganda and South Africa: men and non-pregnant women with early-stage HIV infection (CD4 > 350 cells/μL), pregnant women with early-stage HIV infection and men and non-pregnant women with late-stage HIV infection (CD4 < 200 cells/μL). Socio-behavioural questionnaires were administered and viral loads were performed at 0, 6 and 12 months. Adherence was monitored electronically.

RESULTS

Adherence data were available for 869 participants: 322 (37%) early/non-pregnant, 199 (23%) early/pregnant and 348 (40%) late/non-pregnant participants. In Uganda, median adherence was 89% (interquartile range 74 to 96) and viral suppression was 90% at 12 months; neither differed among groups (p > 0.72). In South Africa, median adherence was higher in early/non-pregnant versus early/pregnant or late/non-pregnant participants (76%, 37%, 52%; p < 0.001), with similar trends in viral suppression (86%, 51%, 79%; p < 0.001). Among early/non-pregnant individuals in Uganda, adherence was higher with increasing age and lower with structural barriers; whereas in South Africa, adherence was higher with regular income, higher perceived stigma and use of other medications, but lower with maladaptive coping and cigarette smoking.

DISCUSSION

ART adherence among non-pregnant individuals with early-stage infection is as high or higher than with late-stage initiation, supporting universal access to ART. Challenges remain for some pregnant women and individuals with late-stage infection in South Africa and highlight the need for differentiated care delivery.

Trajectories of HIV-related internalized stigma and disclosure concerns among ART initiators and non-initiators in South Africa

Background

HIV-related stigma among people living with HIV (PLHIV) is associated with worse health outcomes. We used longitudinal data from a multi-site cohort in South Africa to assess changes over time in stigma after HIV diagnosis and determine whether antiretroviral therapy (ART) initiation is associated with stigma reduction.

Methods

We administered the Internalized AIDS-Related Stigma Scale (IARSS, a six-item dichotomous scale questionnaire) at baseline, three months, and six months to newly diagnosed ART-eligible participants between 2014-2015. A confirmatory factor analysis indicated that the IARSS contained a four-item internalized stigma factor (α=0.80) and a two-item disclosure concerns factor (α=0.75). We fitted multiple logistic regression models specifying internalized stigma/disclosure concerns at six months as the outcome and ART initiation as the predictor of interest.

Results

Of the 500 participants (187 men and 313 women) enrolled, 308 (62%) initiated ART. Internalized stigma declined among people entering care (mean score, 1.0 to 0.7, p<0.01); however, disclosure concerns remained unchanged (percentage endorsing either disclosure concern item, 78% to 77%, p=0.23). These findings were similar between ART initiators and non-initiators. We estimated a statistically significant positive association between ART initiation and disclosure concerns at six months (OR=1.88; 95% CI, 1.20-2.94) but not between ART initiation and internalized stigma at six months (OR=1.15; 95% CI, 0.75-1.78).

Conclusions

Among ART-eligible South African PLHIV entering into HIV care, internalized stigma modestly declined over time but disclosure concerns persisted. PLHIV who initiated ART were more likely to have persistent disclosure concerns over time as compared with those who did not start ART.

Internalized HIV stigma, ART initiation and HIV-1 RNA suppression in South Africa: exploring avoidant coping as a longitudinal mediator

INTRODUCTION

Cross-sectional evidence suggests that internalized HIV stigma is associated with lower likelihoods of antiretroviral therapy (ART) initiation and HIV-1 RNA suppression among people living with HIV (PLWH). This study examined these associations with longitudinal data spanning the first nine months following HIV diagnosis and explored whether avoidant coping mediates these associations.

METHODS

Longitudinal data were collected from 398 South African PLWH recruited from testing centres in 2014 to 2015. Self-report data, including internalized stigma and avoidant coping (denying and distracting oneself from stressors), were collected one week and three months following HIV diagnosis. ART initiation at six months and HIV-1 RNA at nine months were extracted from the South Africa National Health Laboratory Service database. Two path analyses were estimated, one testing associations between internalized stigma, avoidant coping and ART initiation, and the other testing associations between internalized stigma, avoidant coping and HIV-1 RNA suppression.

RESULTS

Participants were 36 years old, on average, and 63% identified as female, 18% as Zulu and 65% as Xhosa. The two path models fit the data well (ART initiation outcome: X2 (7) = 8.14, p = 0.32; root mean square error of approximation (RMSEA) = 0.02; comparative fit index (CFI) = 0.92; HIV-1 RNA suppression outcome: X2 (7)  = 6.58, p = 0.47; RMSEA = 0.00; CFI = 1.00). In both models, internalized stigma one week after diagnosis was associated with avoidant coping at three months, controlling for avoidant coping at one week. In turn, avoidant coping at three months was associated with lower likelihood of ART initiation at six months in the first model and lower likelihood of HIV-1 RNA suppression at nine months in the second model. Significant indirect effects were observed between internalized stigma with ART non-initiation and unsuppressed HIV-1 RNA via the mediator of avoidant coping.

CONCLUSIONS

Internalized stigma experienced soon after HIV diagnosis predicted lower likelihood of ART initiation and HIV-1 RNA suppression over the first year following HIV diagnosis. Avoidant coping played a role in these associations, suggesting that PLWH who internalize stigma engage in greater avoidant coping, which in turn worsens medication- and health-related outcomes. Interventions are needed to address internalized stigma and avoidant coping soon after HIV diagnosis to enhance treatment efforts during the first year after HIV diagnosis.

Estimating retention in HIV care accounting for patient transfers: A national laboratory cohort study in South Africa

BACKGROUND

Systematic reviews have described high rates of attrition in patients with HIV receiving antiretroviral therapy (ART). However, migration and clinical transfer may lead to an overestimation of attrition (death and loss to follow-up). Using a newly linked national laboratory database in South Africa, we assessed national retention in South Africa's national HIV program.

METHODS AND FINDINGS

Patients receiving care in South Africa's national HIV program are monitored through regular CD4 count and viral load testing. South Africa's National Health Laboratory Service has maintained a database of all public-sector CD4 count and viral load results since 2004. We linked individual laboratory results to patients using probabilistic matching techniques, creating a national HIV cohort. Validation of our approach in comparison to a manually matched dataset showed 9.0% undermatching and 9.5% overmatching. We analyzed data on patients initiating ART in the public sector from April 1, 2004, to December 31, 2006, when ART initiation could be determined based on first viral load among those whose treatment followed guidelines. Attrition occurred on the date of a patient's last observed laboratory measure, allowing patients to exit and reenter care prior to that date. All patients had 6 potential years of follow-up, with an additional 2 years to have a final laboratory measurement to be retained at 6 years. Data were censored at December 31, 2012. We assessed (a) national retention including all laboratory tests regardless of testing facility and (b) initiating facility retention, where laboratory tests at other facilities were ignored. We followed 55,836 patients initiating ART between 2004 and 2006. At ART initiation, median age was 36 years (IQR: 30-43), median CD4 count was 150 cells/mm3 (IQR: 81-230), and 66.7% were female. Six-year initiating clinic retention was 29.1% (95% CI: 28.7%-29.5%). After allowing for transfers, national 6-year retention was 63.3% (95% CI: 62.9%-63.7%). Results differed little when tightening or relaxing matching procedures. We found strong differences in retention by province, ranging from 74.2% (95% CI: 73.2%-75.2%) in Western Cape to 52.2% (95% CI: 50.6%-53.7%) in Mpumalanga at 6 years. National attrition was higher among patients initiating at lower CD4 counts and higher viral loads, and among patients initiating ART at larger facilities. The study's main limitation is lack of perfect cohort matching, which may lead to over- or underestimation of retention. We also did not have data from KwaZulu-Natal province prior to 2010.

CONCLUSIONS

In this study, HIV care retention was substantially higher when viewed from a national perspective than from a facility perspective. Our results suggest that traditional clinical cohorts underestimate retention.

Does integrating AIDS treatment with food assistance affect labor supply? Evidence from Zambia

In low income settings, food assistance is increasingly becoming part of AIDS treatment and care programs with the aim of improving adherence to AIDS treatment, enhancing household food security and strengthening economic wellbeing. Yet, evidence of its economic impact is sparse. This paper uses primary data to examine the short term impact of a food assistance program on labor supply as measured by the hours worked, labor market participation rates and transitions to employment within HIV/AIDS affected households in Zambia. We find that food assistance is generally a labor supply disincentive to HIV-infected patients receiving treatment as it reduced their hours worked by up to 54%, transitions to employment by up to 70% and also reduced the labor market participation rates of male patients by 72%. Among non-infected adult family members, there were no significant effects on labor market participation. However, propensity score estimates show that food assistance generally increased the intensity of work by males regardless of the length of AIDS treatment, but for females there was a disincentive effect that disappeared when the patient had spent a longer time on AIDS treatment and was therefore healthier and less likely to be cared for. These findings suggest that food assistance can inadvertently reduce the labor supply of HIV-infected individuals, but this is compensated for by the increased labor supply among other family members.

Understanding data sources to measure patient retention in HIV care in sub-Saharan Africa

Antiretroviral therapy (ART) programs in sub-Saharan Africa are moving towards universal treatment, yet the success of these programs is threatened by gaps within the continuum of HIV care. In this commentary, we seek to draw attention to the advantages and limitations of different data sources currently used for measuring retention in HIV care. Within the context of a piecemeal combination of imperfect data sources, selecting a gold standard of collecting retention data is difficult. Currently, our data systems for measuring retention provide an incomplete picture of the health of our national ART systems and, thus, the health of our patients.