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.

Increased duration of viral suppression is associated with lower viral rebound rates in patients with previous treatment failures.

OBJECTIVE: We investigated whether the rate of viral rebound decreases with increasing duration of viral suppression and, if so, whether rebound rates in patients previously failing antiretroviral regimens ultimately decline to levels as low as those seen in patients who have never experienced virological failure. METHODS: All patients from the UK CHIC Study (n = 21 256) who achieved a viral load (VL) of < or = 50 copies/ml while receiving HAART were followed until viral rebound (two consecutive VL > 400 copies/ml). Patients could re-enter the analysis if they experienced a subsequent VL < or = 50 copies/ml. Rebound rates were calculated according to the number of regimens previously failed and duration of viral suppression. RESULTS: Of 12 648 patients on HAART 10 237 (80.9%) achieved a VL < or = 50 copies/ml. During 26 494 person-years (PY) of follow-up, 1853 (18.1%) patients experienced at least one viral rebound 'event', with 2460 events in total [rebound rate, 9.3 (range, 8.9-9.7)/100 PY). Within the first year of viral suppression, the rate of viral rebound was 8.3 (7.5-9.1)/100 PY in patients who had not previously failed treatment, increasing to 32.7 (27.6-37.8)/100 PY in patients who had failed more than four regimens. Irrespective of previous treatment failure, rebound rates in those who remained suppressed for > 4 years were similar to those in patients who had at no time experienced treatment failure. CONCLUSION: After around 4 years of viral suppression rebound rates in individuals with multiple prior treatment failures approach those of individuals with no prior treatment failure.

Predictors of pregnancy and changes in pregnancy incidence among HIV-positive women accessing HIV clinical care.

OBJECTIVES: To describe predictors of pregnancy and changes in pregnancy incidence among HIV-positive women accessing HIV clinical care. METHODS: Data were obtained through the linkage of two separate studies: the UK Collaborative HIV Cohort study (UK CHIC), a cohort of adults attending 13 large HIV clinics; and the National Study of HIV in Pregnancy and Childhood (NSHPC), a national surveillance study of HIV-positive pregnant women. Pregnancy incidence was measured using the proportion of women in UK CHIC with a pregnancy reported to NSHPC. Generalized estimating equations were used to identify predictors of pregnancy and assess changes in pregnancy incidence in 2000-2009. RESULTS: The number of women accessing care at UK CHIC sites increased as did the number of pregnancies. Older women were less likely to have a pregnancy [adjusted relative rate (aRR) 0.44 per 10 year increment in age, [95% confidence interval (CI) (0.41-0.46)], P < 0.001] as were women with CD4 cell count less than 200 cells/µl compared with CD4 cell count 200-350 cells/µl [aRR 0.65 (0.55-0.77), P < 0.001] and women of white ethnicity compared with women of black African ethnicity [aRR 0.67 (0.57-0.80), P < 0.001]. The likelihood that women had a pregnancy increased over the study period [aRR 1.05 (1.03-1.07), P < 0.001). The rate of change did not significantly differ according to age group, antiretroviral therapy use, CD4 group or ethnicity. CONCLUSION: The pregnancy rate among women accessing HIV clinical care increased in 2000-2009. HIV-positive women with, or planning, a pregnancy require a high level of care and this is likely to continue and increase as more women of older age have pregnancies.

Treatment switches during pregnancy among HIV-positive women on antiretroviral therapy at conception.

OBJECTIVES: To describe antiretroviral therapy (ART) use and clinical status, at start of and during pregnancy, for HIV-positive women receiving ART at conception, including the proportion conceiving on drugs (efavirenz and didanosine) not recommended for use in early pregnancy. METHODS: Women with a pregnancy resulting in a live-birth after 1995 (n = 1537) were identified in an observational cohort of patients receiving HIV care at 12 clinics in the UK by matching records with national pregnancy data. Treatment and clinical data were analysed for 375 women conceiving on ART, including logistic regression to identify factors associated with changing regimen during pregnancy. RESULTS: Of the 375 women on ART, 39 (10%) conceived on dual therapy, 306 (82%) on triple therapy and 30 (8%) on more than three drugs. In total, 116 (31%) women conceived on a regimen containing efavirenz or didanosine (69 efavirenz, 54 didanosine, seven both). Overall, 38% (143) changed regimen during pregnancy, of whom 44% (n = 51) had a detectable viral load around that time. Detectable viral load was associated with increased risk of regimen change [adjusted odds ratio 2.97, 95% confidence interval (CI) (1.70-5.19)], while women on efavirenz at conception were three times more likely to switch than women on other drugs [3.40, (1.84-6.25)]. Regimen switching was also associated with year at conception [0.89, (0.83-0.96)]. CONCLUSION: These findings reinforce the need for careful consideration of ART use among women planning or likely to have a pregnancy in order to reduce viral load before pregnancy and avoid drugs not recommended for early antenatal use.

Are previous treatment interruptions associated with higher viral rebound rates in patients with viral suppression?

OBJECTIVE: We investigated whether previous treatment interruptions are associated with a raised risk of viral rebound in individuals who have attained virological suppression. METHODS: All patients achieving an undetectable viral load while on therapy were followed until viral rebound or the time of the last viral load. Poisson regression was used to describe the independent impact of treatment interruptions on rebound rates. RESULTS: A total of 12,977 patients from the United Kingdom Collaborative HIV Cohort (UK CHIC) Study achieved a viral load of less than 50 copies/ml. These patients contributed a total of 37,314 person-years of follow-up. The overall rebound rate was 8.07 (7.78, 8.36) per 100 person-years. In adjusted analyses, rates of viral rebound were up to 64% higher (rate ratio 1.64; 1.43, 1.88) in those who had previously interrupted therapy compared with those who had not. Patients who had interrupted at detectable viral loads had up to a 74% (1.74; 1.42, 2.14) higher chance of rebounding compared with those who had not interrupted with a detectable viral load. We found no evidence to suggest interrupting treatment at an undetectable viral load was associated with viral rebound. CONCLUSION: Among patients with an undetectable viral load, having previously interrupted therapy while the viral load was detectable is associated with a raised risk of rebound.