Data linkage reduces loss to follow-up in an observational HIV cohort study

A cohort of patients in New York State with an alcohol use disorder and subsequent treatment information - A merging of two administrative data sources

OBJECTIVE

Despite the high prevalence of alcohol use disorder (AUD) in the United States, limited research is focused on the associations among AUD, pain, and opioids/benzodiazepine use. In addition, little is known regarding individuals with a history of AUD and their potential risk for pain diagnoses, pain prescriptions, and subsequent misuse. Moreover, the potential risk of pain diagnoses, prescriptions, and subsequent misuse among individuals with a history of AUD is not well known. The objective was to develop a tailored dataset by linking data from 2 New York State (NYS) administrative databases to investigate a series of hypotheses related to AUD and painful medical disorders.

METHODS

Data from the NYS Office of Addiction Services and Supports (OASAS) Client Data System (CDS) and Medicaid claims data from the NYS Department of Health Medicaid Data Warehouse (MDW) were merged using a stepwise deterministic method. Multiple patient-level identifier combinations were applied to create linkage rules. We included patients aged 18 and older from the OASAS CDS who initially entered treatment with a primary substance use of alcohol and no use of opioids between January 1, 2003, and September 23, 2019. This cohort was then linked to corresponding Medicaid claims.

RESULTS

A total of 177,685 individuals with a primary AUD problem and no opioid use history were included in the dataset. Of these, 37,346 (21.0%) patients had an OUD diagnosis, and 3,365 (1.9%) patients experienced an opioid overdose. There were 121,865 (68.6%) patients found to have a pain condition.

CONCLUSION

The integrated database allows researchers to examine the associations among AUD, pain, and opioids/benzodiazepine use, and propose hypotheses to improve outcomes for at-risk patients. The findings of this study can contribute to the development of a prognostic prediction model and the analysis of longitudinal outcomes to improve the care of patients with AUD.

Deterministic linkage for improving follow-up time in a Brazilian population-based cancer registry

Population-based cancer registries (PBCR) are the primary source of cancer incidence and survival statistics. The loss to follow-up of these patients is concerning since it reduces the reliability of any statistical analysis. The linkage techniques have been increasingly used to improve data quality in various information systems. The linkage was performed between the databases of the PBCR-Barretos and the mortality database of the state of São Paulo. To evaluate the improvement in the follow-up time of patients, the comparability of the two databases, pre- and post linkage, was made. Three analyses were performed: a comparative analysis of the absolute number of deaths, a comparative analysis of the follow-up time of patients and the survival analysis. After linkage, there was an increase of 813 deaths. The follow-up time of patients was extended and observed in most types of tumours. The comparability of the survival analyses at both time points also showed a decrease in survival probabilities for all tumour types. Deterministic linkage is effective in updating the vital status of registered patients, improving patient follow-up time, and maintaining good quality data from PBCRs, consequently producing more reliable rates, as seen for the survival analyses.

HIV Viral Suppression among People Living with HIV on Antiretroviral Therapy in Haut-Katanga and Kinshasa Provinces of Democratic Republic of Congo

Human immunodeficiency virus (HIV) infections and less-than-optimal care of people living with HIV (PLHIV) continue to challenge public health and clinical care organizations in the communities that are most impacted by HIV. In the era of evidence-based public health, it is imperative to monitor viral load (VL) in PLHIV according to global and national guidelines and assess the factors associated with variation in VL levels. Purpose: This study had two objectives—(a) to describe the levels of HIV VL in persons on antiretroviral therapy (ART), and (b) to analyze the significance of variation in VL by patients’ demographic and clinical characteristics, outcomes of HIV care, and geographic characteristics of HIV care facilities. Methods: The study population for this quantitative study was 49,460 PLHIV in the Democratic Republic of Congo (DRC) receiving ART from 241 CDC-funded HIV/AIDS clinics in the Haut-Katanga and Kinshasa provinces of the DRC. Analysis of variance (ANOVA) was performed, including Tamhane’s T2 test for pairwise comparisons using de-identified data on all patients enrolled in the system by the time the data were extracted for this study by the HIV programs in May 2019. Results: The VL was undetectable (<40 copies/mL) for 56.4% of the patients and 24.7% had VL between 40 copies/mL and less than 1000 copies per mL, indicating that overall, 81% had VL < 1000 and were virologically suppressed. The remaining 19% had a VL of 1000 copies/mL or higher. The mean VL was significantly (p < 0.001) higher for males than for females (32,446 copies/mL vs. 20,786, respectively), persons <15 years of age compared to persons of ages ≥ 15 years at the time of starting ART (45,753 vs. 21,457, respectively), patients who died (125,086 vs. 22,090), those who were lost to follow-up (LTFU) (69,882 vs. 20,018), those with tuberculosis (TB) co-infection (64,383 vs. 24,090), and those who received care from urban clinics (mean VL = 25,236) compared to rural (mean VL = 3291) or semi-rural (mean VL = 26,180) clinics compared to urban. WHO clinical stages and duration on ART were not statistically significant at p ≤ 0.05 in this cohort. Conclusions: The VL was >1000 copies/mL for 19% of PLHIV receiving ART, indicating that these CDC-funded clinics and programs in the Haut-Katanga and Kinshasa provinces of DRC have more work to do. Strategically designed innovations in services are desirable, with customized approaches targeting PLHIV who are younger, male, those LTFU, with HIV/TB co-infection, and those receiving care from urban clinics.

Data linkage to evaluate the long-term risk of HIV infection in individuals seeking post-exposure prophylaxis

Evidence on the long-term risk of HIV infection in individuals taking HIV post-exposure prophylaxis remains limited. In this retrospective data linkage study, we evaluate the occurrence of HIV infection in 975 individuals who sought post-exposure prophylaxis in a tertiary hospital between 2007 and 2013. Using privacy preserving probabilistic linkage, we link these 975 records with two observational databases providing data on HIV events (Zurich Primary HIV Infection study and the Swiss HIV Cohort Study). This enables us to identify 22 HIV infections and to obtain long-term follow-up data, which reveal a median of 4.1 years between consultation for post-exposure prophylaxis and HIV diagnosis. Even though men who have sex with men constitute only 35.8% of those seeking post-exposure prophylaxis, all 22 events occur in this subgroup. These findings should strongly encourage early consideration of pre-exposure prophylaxis in men who have sex with men after a first episode of post-exposure prophylaxis.

Individuals seeking post-exposure prophylaxis (PEP) for HIV may represent an important risk group for future HIV infection. Here the authors find HIV infections at long-term follow-up in 22 of 348 men who have sex with men, and 0 of 623 other PEP seekers.

Loss to follow-up and associated factors of patients in the National AIDS Program in Thailand

BACKGROUND

Loss to follow-up (LTFU) is a crucial indicator to evaluate the effectiveness of HIV care and treatment programmes. We assessed the LTFU rate and associated factors of Thai HIV-infected patients who enrolled in the National AIDS Program (NAP) for two periods: prior to (pre-ART) and after starting ART (ART-patients).

METHODS

Thai HIV patients aged ≥15 years enrolled in NAP from 2008 to 2014. Vital status was ascertained by linkage with the National Death Registry. Competing risk models were used to calculate the adjusted sub-distribution hazards (aSHR) for LTFU for pre-ART and ART-patients, with death considered as a competing risk.

RESULTS

A total of 157,026 patients registered in care and were included in analyses. The cumulative incidence of LTFU in pre-ART patients at 1 year was 10.2%, whereas in ART-patients it was 12.8%. Among pre-ART patients, younger age (<30 versus ≥45 years, aSHR 1.60, 95% CI 1.49, 1.72), less advanced HIV stage (aSHR 1.29, 95% CI 1.21, 1.37) and higher CD4⁺ T-cell count (≥350 versus <100, aSHR 6.31, 95% CI 5.74, 6.95) had a higher chance of LTFU. ART-patients with high baseline CD4⁺ T-cell count (CD4 ≥350 versus CD4 <50, aSHR 2.06, 95% CI 1.97, 2.15) and non-advanced HIV stage had increased risk of LTFU.

CONCLUSIONS

Our findings provide new evidence of the LTFU rate in Thai HIV-infected patients in NAP. Emphasis needs to be placed on improving follow-up in all patients with higher CD4⁺ T-cell counts. LTFU will be important to monitor as programmes move to commence ART regardless of CD4⁺ T-cell count.

Are there differences in HIV retention in care between female and male patients in Indonesia? A multi-state analysis of a retrospective cohort study

BACKGROUND

Little is known about HIV treatment outcomes in Indonesia, which has one of the most rapidly growing HIV epidemics worldwide.

METHODS

We examined possible differences in loss to follow-up (LTFU) and survival between HIV-infected females and males over a 7-year period in an HIV clinic in Bandung, West Java. Data imputation was performed on missing covariates and a multi-state Cox regression was used to investigate the effects of sex and other covariates on patient transitions among four states: (1) clinic enrollment with HIV, (2) initiation/continuation/re-initiation of antiretroviral therapy (ART), (3) LTFU, and (4) death.

RESULTS

We followed 3215 patients (33% females), for a total of 8430 person-years. ART was used by 59% of patients at some point. One-year retention was 73% for females and 77% for males (p = 0.06). One-year survival was 98% for both females and males (p = 0.15). Females experienced a higher relative hazard to transition from HIV to LTFU (adjusted hazard ratio 1.21; 95% confidence interval 1.00-1.45), but this decreased after adjustments for clinical variables (aHR 0.94; 95% CI 0.79-1.11). Similarly, a lower relative hazard in females to transition from ART to death (aHR 0.59; 95% CI 0.35-0.99) decreased after adjustments for demographic variables.

CONCLUSION

This Indonesian cohort has low ART uptake and poor overall pre- and post-ART retention. Female-male differences in survival and retention were gone after adjusting for clinical and sociodemographic factors such as CD4 count and education level. Efforts should be made to improve retention among patients with lower education.

Predictors associated with HIV/AIDS patients dropout from antiretroviral therapy at Mettu Karl Hospital, southwest Ethiopia

OBJECTIVE

The aim of this study was to determine the major risk factors of antiretroviral therapy dropout. The retrospective cohort research design was applied. 1512 HIV patients were included from Mettu Karl Hospital in Illubabor Zone, southwest part of Ethiopia from September 2005 to January 2018. Kaplan-Meier comparison and log-logistic regression accelerated failure time model were used.

RESULTS

From the log-logistic regression result, the risk of dropout for patients with primary education status was 10.58% greater as compared to illiterate (p < 0.0110). The probability of dropout for patients with marital status separated was about 16.82% higher than those patients with marital status divorced (p < 0.0070). Being merchant, farmer and daily labour had a greater risk of dropout as compared to a housewife. Most of the HIV/AIDS patients on ART were dropout in a short period due to patients separated marital status, primary education, CD4, being merchants, farmer and daily labour. Investigation on the cause of antiretroviral therapy dropout from a number of AIDS clinics in the country is highly appreciated.

Gonorrhoea and chlamydia diagnosis as an entry point for HIV pre-exposure prophylaxis: a modelling study

OBJECTIVES

Neisseria gonorrhoeae (NG) and Chlamydia trachomatis (CT) increase the risk of HIV transmission among men who have sex with men (MSM). Diagnosis of NG/CT may provide an efficient entry point for prevention of HIV through the delivery of pre-exposure prophylaxis (PrEP); however, the additional population-level impact of targeting PrEP to MSM diagnosed with NG/CT is unknown.

DESIGN

An agent-based simulation model of NG/CT and HIV cocirculation among MSM calibrated against census data, disease surveillance reports and the US National HIV Behavioral Surveillance study.

SETTING

Baltimore City, Maryland, USA.

INTERVENTIONS

PrEP implementation was modelled under three alternative scenarios: (1) PrEP delivery at NG/CT diagnosis (targeted delivery), (2) PrEP evaluation at NG/CT screening/testing and (3) PrEP evaluation in the general community (untargeted).

MAIN OUTCOME

The projected incidence of HIV after 20 years of PrEP delivery under two alternatives: when equal numbers of MSM are (1) screened for PrEP or (2) receive PrEP in each year.

RESULTS

Assuming 60% uptake and 60% adherence, targeting PrEP to MSM diagnosed with NG/CT could reduce HIV incidence among MSM in Baltimore City by 12.4% (95% uncertainty range (UR) 10.3% to 14.4%) in 20 years, relative to no PrEP. Expanding the coverage of NG/CT screening (such that individuals experience a 50% annual probability of NG/CT screening and evaluation for PrEP on NG/CT diagnosis) can further increase the impact of targeted PrEP to generate a 22.0% (95% UR 20.1% to 23.9%) reduction in HIV incidence within 20 years. When compared with alternative implementation scenarios, PrEP evaluation at NG/CT diagnosis increased impact of PrEP on HIV incidence by 1.5(95% UR 1.1 to 1.9) times relative to a scenario in which PrEP evaluation happened at the time of NG/CT screening/testing and by 1.6 (95% UR 1.2 to 2.2) times relative to evaluating random MSM from the community.

CONCLUSIONS

Targeting MSM infected with NG/CT increases the efficiency and effectiveness of PrEP delivery. If high levels of sexually transmitted infection screening can be achieved at the community level, NG/CT diagnosis may be a highly effective entry point for PrEP initialisation.

The Chang Gung Research Database-A multi-institutional electronic medical records database for real-world epidemiological studies in Taiwan

PURPOSE

The Chang Gung Research Database (CGRD), the largest multi-institutional electronic medical records (EMR) collection in Taiwan, provides good access for researchers to efficiently use the standardized patient-level data. This study evaluates the capacity and representativeness of the CGRD to promote secondary use of EMR data for clinical research with more accurate estimates.

METHODS

The National Health Insurance Research Database (NHIRD) which covers over 99.9% of the Taiwanese population served as the comparator in this study. We compare the data components of the CGRD with the NHIRD, including records for health care facilities, patients, diagnoses, drugs, and procedures. Using the chi-square test, we compared the distributions of age categories and sex of patients, and the rates of their health conditions between NHIRD and CGRD based on the year 2015.

RESULTS

The CGRD contains more clinical information such as pathological and laboratory results than the NHIRD. The CGRD includes 6.1% of outpatients and 10.2% of hospitalized patients from the NHIRD. We found the CGRD includes more elderly outpatients (23.5% vs 12.5%) and pediatric inpatients (19.7% vs 14.4%) compared with the NHIRD. We found patients' sex distributions were similar between CGRD and NHIRD, but coverage rates of severe conditions, such as cancer, were higher than other health conditions in CGRD.

CONCLUSIONS

The CGRD could serve as the basis for accurate estimates in medical studies. However, researchers should pay special attention to selection biases since patients' characteristics from CGRD differ from those of the national database.

REACH: a mixed-methods study to investigate the measurement, prediction and improvement of retention and engagement in outpatient HIV care

Background

Antiretroviral therapy (ART) benefits individuals living with human immunodeficiency virus (HIV) through reduced morbidity and mortality, and brings public health gains through a reduction in HIV transmission. People living with human immunodeficiency virus (PLWH) need to know their HIV status and engage in HIV care in order for these individual and public health benefits to be realised.

Objective

To explore, describe and understand HIV outpatient attendance in PLWH, in order to develop cost-effective interventions to optimise engagement in care.

Design

A mixed-methods study incorporating secondary analysis of data from the UK Collaborative HIV Cohort (UK CHIC) study and primary data collection.

Methods

Phase 1 – an engagement-in-care (EIC) algorithm was developed to categorise patients as in care or out of care for each month of follow-up. The algorithm was used in group-based trajectory analysis to examine patterns of attendance over time and of the association between the proportion of months in care before ART initiation and post-ART mortality and laboratory test costs. Phase 2 – a cross-sectional survey was conducted among patients attending seven London HIV clinics. Regular attenders (all appointments attended in past year), irregular attenders (one or more appointments missed in past year) and non-attenders (recent absence of ≥ 1 year) were recruited. A ‘retention risk tool’ was developed to identify those at risk of disengaging from care. Individual in-depth interviews and focus groups were conducted with PLWH. Phase 3 – key informant interviews were conducted with HIV service providers. Interventions were developed from the findings of phases 2 and 3.

Results

Plots from group-based trajectory analysis indicated that four trajectories best fitted the data. Higher EIC is associated with reduced mortality but the association between EIC before starting ART, and post-ART mortality [relative hazard (RH) per 10% increase in EIC 0.29, 95% confidence interval (CI) 0.18 to 0.47] was attenuated after adjustment for fixed covariates and post-ART cluster of differentiation 4 counts and viral loads (RH 0.74, 95% CI 0.42 to 1.30). Small differences were found in pre-ART EIC and the costs of post-ART lab tests. The final model for the retention risk tool included age at diagnosis, having children, recreational drug use, drug/alcohol dependency, insufficient money for basic needs and use of public transport to get to the clinic. Quantitative and qualitative data showed that a range of psychological, social and economic issues were associated with disengagement from care. The negative impact of stigma on attendance was highlighted. Interventions were proposed that support a holistic approach to care including peer support, address stigma by holding clinics in alternative locations and involve training staff to encourage attendance.

Conclusions

The study shows the adverse health impacts of disengaging from HIV care and demonstrates the importance of the wider health and social context in managing HIV effectively. Although phase 1 analysis was based on UK data, phases 2 and 3 were limited to London. The interventions proposed are supported by the data but their cost-effectiveness requires testing. Future research is needed to evaluate the interventions, to validate our retention risk tool across populations and settings, and to fully analyse the economic costs of disengaging from HIV care.

Funding

The National Institute for Health Research Health Services and Delivery Research programme. The UK CHIC study is funded by the Medical Research Council UK (grant numbers G0000199, G0600337, G0900274 and M004236).

Pregnant women with HIV in rural Nigeria have higher rates of antiretroviral treatment initiation, but similar loss to follow-up as non-pregnant women and men

BACKGROUND

We examined antiretroviral therapy (ART) initiation and retention by sex and pregnancy status in rural Nigeria.

METHODS

We studied HIV-infected ART-naïve patients aged ≥15 years entering care from June 2009 to September 2013. We calculated the probability of early ART initiation and cumulative incidence of loss to follow-up (LTFU) during the first year of ART, and examined the association between LTFU and sex/pregnancy using Cox regression.

RESULTS

The cohort included 3813 ART-naïve HIV-infected adults (2594 women [68.0%], 273 [11.8%] of them pregnant). The proportion of pregnant clients initiating ART within 90 days of enrollment (78.0%, 213/273) was higher than among non-pregnant women (54.3%,1261/2321) or men (53.0%, 650/1219), both p<0.001. Pregnant women initiated ART sooner than non-pregnant women and men (median [IQR] days from enrollment to ART initiation for pregnant women=7 days [0-21] vs 14 days [7-49] for non-pregnant women and 14 days [7-42] for men; p<0.001). Cumulative incidence of LTFU during the first year post-ART initiation was high and did not differ by sex and pregnancy status. Persons who were unemployed, bedridden, had higher CD4+ counts, and/or in earlier WHO clinical stages were more likely to be LTFU.

CONCLUSIONS

Pregnant women with HIV in rural Nigeria were more likely to initiate ART but were no more likely to be retained in care. Our findings underscore the importance of effective retention strategies across all patient groups, regardless of sex and pregnancy status.

Loss to follow-up in the Australian HIV Observational Database

BACKGROUND

Loss to follow-up (LTFU) in HIV-positive cohorts is an important surrogate for interrupted clinical care, which can potentially influence the assessment of HIV disease status and outcomes. After preliminary evaluation of LTFU rates and patient characteristics, we evaluated the risk of mortality by LTFU status in a high-resource setting.

METHODS

Rates of LTFU were measured in the Australian HIV Observational Database for a range of patient characteristics. Multivariate repeated measures regression methods were used to identify determinants of LTFU. Mortality by LTFU status was ascertained using linkage to the National Death Index. Survival following combination antiretroviral therapy initiation was investigated using the Kaplan-Meier (KM) method and Cox proportional hazards models.

RESULTS

Of 3,413 patients included in this analysis, 1,632 (47.8%) had at least one episode of LTFU after enrolment. Multivariate predictors of LTFU included viral load (VL)>10,000 copies/ml (rate ratio [RR] 1.63; 95% CI 1.45, 1.84; ref ≤400), time under follow-up (per year; RR 1.03; 95% CI 1.02, 1.04) and prior LTFU (per episode; RR 1.15; 95% CI 1.06, 1.24). KM curves for survival were similar by LTFU status (P=0.484). LTFU was not associated with mortality in Cox proportional hazards models (univariate hazard ratio [HR] 0.93; 95% CI 0.69, 1.26) and multivariate HR 1.04 (95% CI 0.77, 1.43).

CONCLUSIONS

Increased risk of LTFU was identified amongst patients with potentially higher infectiousness. We did not find significant mortality risk associated with LTFU. This is consistent with timely re-engagement with treatment, possibly via high levels of unreported linkage to other health-care providers.

Loss to clinic and five-year mortality among HIV-infected antiretroviral therapy initiators

Missing outcome data due to loss to follow-up occurs frequently in clinical cohort studies of HIV-infected patients. Censoring patients when they become lost can produce inaccurate results if the risk of the outcome among the censored patients differs from the risk of the outcome among patients remaining under observation. We examine whether patients who are considered lost to follow up are at increased risk of mortality compared to those who remain under observation. Patients from the US Centers for AIDS Research Network of Integrated Clinical Systems (CNICS) who newly initiated combination antiretroviral therapy between January 1, 1998 and December 31, 2009 and survived for at least one year were included in the study. Mortality information was available for all participants regardless of continued observation in the CNICS. We compare mortality between patients retained in the cohort and those lost-to-clinic, as commonly defined by a 12-month gap in care. Patients who were considered lost-to-clinic had modestly elevated mortality compared to patients who remained under observation after 5 years (risk ratio (RR): 1.2; 95% CI: 0.9, 1.5). Results were similar after redefining loss-to-clinic as 6 months (RR: 1.0; 95% CI: 0.8, 1.3) or 18 months (RR: 1.2; 95% CI: 0.8, 1.6) without a documented clinic visit. The small increase in mortality associated with becoming lost to clinic suggests that these patients were not lost to care, rather they likely transitioned to care at a facility outside the study. The modestly higher mortality among patients who were lost-to-clinic implies that when we necessarily censor these patients in studies of time-varying exposures, we are likely to incur at most a modest selection bias.

Predictors of non-adherence to clinical follow-up among patients participating in a randomized trial of pharmaceutical care intervention in HIV-positive adults in Southern Brazil

Pharmaceutical care (PC) has been shown to improve adherence to therapeutic interventions as well as improve clinical outcomes. We assessed the predictors of non-adherence to clinical follow-up (i.e., not attending three scheduled routine clinical visits over a 1 year period) among patients who participated in a clinical trial of PC intervention on adherence to HIV antiretroviral therapy uptake (the PC-HIV trial). A total of 332 patients participated: median age was 39 years, 63 % were male, 76 % had CD4 count ≥200 cells/mm³, and 52 % had undetectable viral load. About half, 52.7 %, were non-adherent to clinical follow-up. Identified risk factors for non-adherence were male gender, age <40 years, and being in the trial's "control" group (adjusted odds ratio [AOR] 1.67, 95 % CI 1.05-2.66; AOR 2.21, 95 % CI 1.42-3.47; AOR 1.67, 95 % CI 1.07-2.61, respectively). Younger, male patients may benefit from interventions such as PC, which facilitates engagement in care.

Heterogeneity in outcomes of treated HIV-positive patients in Europe and North America: relation with patient and cohort characteristics

BACKGROUND

HIV cohort collaborations, which pool data from diverse patient cohorts, have provided key insights into outcomes of antiretroviral therapy (ART). However, the extent of, and reasons for, between-cohort heterogeneity in rates of AIDS and mortality are unclear.

METHODS

We obtained data on adult HIV-positive patients who started ART from 1998 without a previous AIDS diagnosis from 17 cohorts in North America and Europe. Patients were followed up from 1 month to 2 years after starting ART. We examined between-cohort heterogeneity in crude and adjusted (age, sex, HIV transmission risk, year, CD4 count and HIV-1 RNA at start of ART) rates of AIDS and mortality using random-effects meta-analysis and meta-regression.

RESULTS

During 61 520 person-years, 754/38 706 (1.9%) patients died and 1890 (4.9%) progressed to AIDS. Between-cohort variance in mortality rates was reduced from 0.84 to 0.24 (0.73 to 0.28 for AIDS rates) after adjustment for patient characteristics. Adjusted mortality rates were inversely associated with cohorts' estimated completeness of death ascertainment [excellent: 96-100%, good: 90-95%, average: 75-89%; mortality rate ratio 0.66 (95% confidence interval 0.46-0.94) per category]. Mortality rate ratios comparing Europe with North America were 0.42 (0.31-0.57) before and 0.47 (0.30-0.73) after adjusting for completeness of ascertainment.

CONCLUSIONS

Heterogeneity between settings in outcomes of HIV treatment has implications for collaborative analyses, policy and clinical care. Estimated mortality rates may require adjustment for completeness of ascertainment. Higher mortality rate in North American, compared with European, cohorts was not fully explained by completeness of ascertainment and may be because of the inclusion of more socially marginalized patients with higher mortality risk.

Using two on-going HIV studies to obtain clinical data from before, during and after pregnancy for HIV-positive women

Background

The UK Collaborative HIV Cohort (UK CHIC) is an observational study that collates data on HIV-positive adults accessing HIV clinical care at (currently) 13 large clinics in the UK but does not collect pregnancy specific data. The National Study of HIV in Pregnancy and Childhood (NSHPC) collates data on HIV-positive women receiving antenatal care from every maternity unit in the UK and Ireland. Both studies collate pseudonymised data and neither dataset contains unique patient identifiers. A methodology was developed to find and match records for women reported to both studies thereby obtaining clinical and treatment data on pregnant HIV-positive women not available from either dataset alone.

Results

Women in UK CHIC receiving HIV-clinical care in 1996–2009, were found in the NSHPC dataset by initially ‘linking’ records with identical date-of-birth, linked records were then accepted as a genuine ‘match’, if they had further matching fields including CD4 test date. In total, 2063 women were found in both datasets, representing 23.1% of HIV-positive women with a pregnancy in the UK (n = 8932). Clinical data was available in UK CHIC following most pregnancies (92.0%, 2471/2685 pregnancies starting before 2009). There was bias towards matching women with repeat pregnancies (35.9% (741/2063) of women found in both datasets had a repeat pregnancy compared to 21.9% (1502/6869) of women in NSHPC only) and matching women HIV diagnosed before their first reported pregnancy (54.8% (1131/2063) compared to 47.7% (3278/6869), respectively).

Conclusions

Through the use of demographic data and clinical dates, records from two independent studies were successfully matched, providing data not available from either study alone.

A causal framework for understanding the effect of losses to follow-up on epidemiologic analyses in clinic-based cohorts: the case of HIV-infected patients on antiretroviral therapy in Africa

Although clinic-based cohorts are most representative of the "real world," they are susceptible to loss to follow-up. Strategies for managing the impact of loss to follow-up are therefore needed to maximize the value of studies conducted in these cohorts. The authors evaluated adult patients starting antiretroviral therapy at an HIV/AIDS clinic in Uganda, where 29% of patients were lost to follow-up after 2 years (January 1, 2004-September 30, 2007). Unweighted, inverse probability of censoring weighted (IPCW), and sampling-based approaches (using supplemental data from a sample of lost patients subsequently tracked in the community) were used to identify the predictive value of sex on mortality. Directed acyclic graphs (DAGs) were used to explore the structural basis for bias in each approach. Among 3,628 patients, unweighted and IPCW analyses found men to have higher mortality than women, whereas the sampling-based approach did not. DAGs encoding knowledge about the data-generating process, including the fact that death is a cause of being classified as lost to follow-up in this setting, revealed "collider" bias in the unweighted and IPCW approaches. In a clinic-based cohort in Africa, unweighted and IPCW approaches-which rely on the "missing at random" assumption-yielded biased estimates. A sampling-based approach can in general strengthen epidemiologic analyses conducted in many clinic-based cohorts, including those examining other diseases.

Retention in a public healthcare system with free access to treatment: a Danish nationwide HIV cohort study

OBJECTIVE

We aimed to assess retention of HIV-infected individuals in the Danish healthcare system over a 15-year period.

METHODS

Loss to follow-up (LTFU) was defined as 365 days without contact to the HIV care system. Data were obtained from the nationwide Danish HIV Cohort study, The Danish National Hospital Registry and The Danish Civil Registration System. Incidence rates, risk factors for LTFU and return to care and mortality rate ratios (MRRs) were estimated using Poisson regression analyses.

RESULTS

We included 4745 HIV patients who were followed for 36,692 person-years. Patients were retained in care 95.0% of person-years under observation, increasing to 98.1% after initiation of highly active antiretroviral treatment (HAART). The overall incidence rate/100 person-years for first episode of LTFU was 2.6 [95% confidence interval (CI) 2.5-2.8] and was significantly lower after initiation of HAART [1.2 (95% CI 1.0-1.3)]. Five years after LTFU the probability of return to care was 0.87 (95% CI 0.84-0.90). The risk of death was significantly increased after LTFU [MRR 1.9 (95% CI 1.6-2.6)] and 6 months or less after return to care [MRR 10.9 (95% CI 5.9-19.9)].

CONCLUSION

Retention in care of Danish HIV patients is high, especially after initiation of HAART. Absence from HIV care is associated with increased mortality. We conclude that high rates of retention can be achieved in a healthcare system with free access to treatment and is associated with a favorable outcome.

Loss to Followup in HIV-Infected Patients from Asia-Pacific Region: Results from TAHOD

This study examined characteristics of HIV-infected patients in the TREAT Asia HIV Observational Database who were lost to follow-up (LTFU) from treatment and care. Time from last clinic visit to 31 March 2009 was analysed to determine the interval that best classified LTFU. Patients defined as LTFU were then categorised into permanently LTFU (never returned) and temporary LTFU (re-entered later), and these groups compared. A total of 3626 patients were included (71% male). No clinic visits for 180 days was the best-performing LTFU definition (sensitivity 90.6%, specificity 92.3%). During 7697 person-years of follow-up, 1648 episodes of LFTU were recorded (21.4 per 100-person-years). Patients LFTU were younger (P = 0.002), had HIV viral load ≥500 copies/mL or missing (P = 0.021), had shorter history of HIV infection (P = 0.048), and received no, single- or double-antiretroviral therapy, or a triple-drug regimen containing a protease inhibitor (P < 0.001). 48% of patients LTFU never returned. These patients were more likely to have low or missing haemoglobin (P < 0.001), missing recent HIV viral load (P < 0.001), negative hepatitis C test (P = 0.025), and previous temporary LTFU episodes (P < 0.001). Our analyses suggest that patients not seen at a clinic for 180 days are at high risk of permanent LTFU, and should be aggressively traced.

Long-term follow-up of children with confirmed newborn screening disorders using record linkage

BACKGROUND

Long-term follow-up of children identified through newborn screening is a critical process of data collection and analysis for advancing the public health understanding of the health outcomes and service uptake of the affected children. This article describes first steps toward the long-term follow-up of newborn screening children with confirmed disorders through records linkage using population-based administrative data.

METHODS

The study cohort consisted of children born in 2006-2007 with confirmed disorders identified through newborn screening. Deterministic data linkage methods were used for record matching.

RESULTS

The cohort was followed up to 2 years after birth by matching to data sources including vital records, hospital discharges, the Congenital Malformations Registry, and Early Intervention to monitor service utilization, comorbidities, and mortality of the affected children. Of 1215 children with confirmed conditions identified through newborn screening, 25 deaths (2.1%) were identified, 86.1% used hospital (in- or outpatient) services, 36.1% were enrolled in the Congenital Malformations Registry, and 19.9% used the services of the Early Intervention program during the 2-year follow-up period.

CONCLUSIONS

Long-term follow-up of children with disorders identified through newborn screening can be initiated by using existing administrative data. This method is an inexpensive, cost-effective. and efficient approach for periodical assessment of services utilization, the efficiency of service delivery, and health outcomes for affected individuals.

Estimating loss to follow-up in HIV-infected patients on antiretroviral therapy: the effect of the competing risk of death in Zambia and Switzerland

BACKGROUND

Loss to follow-up (LTFU) is common in antiretroviral therapy (ART) programmes. Mortality is a competing risk (CR) for LTFU; however, it is often overlooked in cohort analyses. We examined how the CR of death affected LTFU estimates in Zambia and Switzerland.

METHODS AND FINDINGS

HIV-infected patients aged ≥18 years who started ART 2004-2008 in observational cohorts in Zambia and Switzerland were included. We compared standard Kaplan-Meier curves with CR cumulative incidence. We calculated hazard ratios for LTFU across CD4 cell count strata using cause-specific Cox models, or Fine and Gray subdistribution models, adjusting for age, gender, body mass index and clinical stage. 89,339 patients from Zambia and 1,860 patients from Switzerland were included. 12,237 patients (13.7%) in Zambia and 129 patients (6.9%) in Switzerland were LTFU and 8,498 (9.5%) and 29 patients (1.6%), respectively, died. In Zambia, the probability of LTFU was overestimated in Kaplan-Meier curves: estimates at 3.5 years were 29.3% for patients starting ART with CD4 cells <100 cells/µl and 15.4% among patients starting with ≥ 350 cells/µL. The estimates from CR cumulative incidence were 22.9% and 13.6%, respectively. Little difference was found between naïve and CR analyses in Switzerland since only few patients died. The results from Cox and Fine and Gray models were similar: in Zambia the risk of loss to follow-up and death increased with decreasing CD4 counts at the start of ART, whereas in Switzerland there was a trend in the opposite direction, with patients with higher CD4 cell counts more likely to be lost to follow-up.

CONCLUSIONS

In ART programmes in low-income settings the competing risk of death can substantially bias standard analyses of LTFU. The CD4 cell count and other prognostic factors may be differentially associated with LTFU in low-income and high-income settings.

Incidence rate of and factors associated with loss to follow-up in a longitudinal cohort of antiretroviral-treated HIV-infected persons: an AIDS Clinical Trials Group (ACTG) Longitudinal Linked Randomized Trials (ALLRT) analysis

PURPOSE

Examine incidence and factors associated with loss to follow-up (LTFU) in the AIDS Clinical Trials Group (ACTG) Longitudinal Linked Randomized Trials (ALLRT) cohort.

METHOD

ALLRT is a prospective cohort of HIV-infected persons randomized to antiretroviral (ARV) regimens/strategies in ACTG trials and followed long-term after the trial ends. Person-years were calculated from ALLRT entry until loss to follow-up (LTFU; defined using off-study reasons or ≥ 3 consecutive missed visits), death/ severe debilitation/site closures, or June 2009 (censored). Poisson regression was used to examine LTFU factors separately among participants who were ARV naïve or ARV experienced at trial entry.

RESULTS

Among 4,630 participants (22,524 person-years), 1,140 were lost to follow-up, 237 died, 29 were severely debilitated, and 443 were at sites that closed. The LTFU incidence was 5.5 and 4.2 per 100 person-years among previously ARV-naïve and ARV-experienced participants, respectively. In both groups, age ≤ 50, site location, being off ARVs, and viral load ≥ 400 copies/mL were associated with a higher risk of LTFU. Among ARV-naïve participants, male sex, education <16 years, intravenous drug use, and cigarette smoking were also associated with LTFU.

CONCLUSION

Knowledge of differential LTFU can help researchers identify participants at risk of LTFU in longitudinal HIV cohorts and design retention strategies, thereby limiting study bias. The identified factors should be included in inverse probability of weighting models to account for LTFU.

Impact of late diagnosis and treatment on life expectancy in people with HIV-1: UK Collaborative HIV Cohort (UK CHIC) Study

OBJECTIVES

To estimate life expectancy for people with HIV undergoing treatment compared with life expectancy in the general population and to assess the impact on life expectancy of late treatment, defined as CD4 count <200 cells/mm(3) at start of antiretroviral therapy.

DESIGN

Cohort study.

SETTING

Outpatient HIV clinics throughout the United Kingdom. Population Adult patients from the UK Collaborative HIV Cohort (UK CHIC) Study with CD4 count ≤ 350 cells/mm(3) at start of antiretroviral therapy in 1996-2008.

MAIN OUTCOME MEASURES

Life expectancy at the exact age of 20 (the average additional years that will be lived by a person after age 20), according to the cross sectional age specific mortality rates during the study period.

RESULTS

1248 of 17,661 eligible patients died during 91,203 person years' follow-up. Life expectancy (standard error) at exact age 20 increased from 30.0 (1.2) to 45.8 (1.7) years from 1996-9 to 2006-8. Life expectancy was 39.5 (0.45) for male patients and 50.2 (0.45) years for female patients compared with 57.8 and 61.6 years for men and women in the general population (1996-2006). Starting antiretroviral therapy later than guidelines suggest resulted in up to 15 years' loss of life: at age 20, life expectancy was 37.9 (1.3), 41.0 (2.2), and 53.4 (1.2) years in those starting antiretroviral therapy with CD4 count <100, 100-199, and 200-350 cells/mm(3), respectively.

CONCLUSIONS

Life expectancy in people treated for HIV infection has increased by over 15 years during 1996-2008, but is still about 13 years less than that of the UK population. The higher life expectancy in women is magnified in those with HIV. Earlier diagnosis and subsequent timely treatment with antiretroviral therapy might increase life expectancy.

The spectrum of engagement in HIV care and its relevance to test-and-treat strategies for prevention of HIV infection

For individuals with human immunodeficiency virus (HIV) infection to fully benefit from potent combination antiretroviral therapy, they need to know that they are HIV infected, be engaged in regular HIV care, and receive and adhere to effective antiretroviral therapy. Test-and-treat strategies for HIV prevention posit that expanded testing and earlier treatment of HIV infection could markedly decrease ongoing HIV transmission, stemming the HIV epidemic. However, poor engagement in care for HIV-infected individuals will substantially limit the effectiveness of test-and-treat strategies. We review the spectrum of engagement in care for HIV-infected individuals in the United States and apply this information to help understand the magnitude of the challenges that poor engagement in care will pose to test-and-treat strategies for HIV prevention.