Open Access Research article

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

Susie E Huntington12*, Loveleen K Bansi1, Claire Thorne2, Jane Anderson3, Marie-Louise Newell24, Graham P Taylor5, Deenan Pillay16, Teresa Hill1, Pat A Tookey2, Caroline A Sabin1 and on behalf of the UK Collaborative HIV Cohort (UK CHIC) Study and the National Study of HIV in Pregnancy and Childhood (NSHPC)

Author Affiliations

1 Research Department of Infection & Population Health, University College London, Royal Free Campus, Rowland Hill Street, London, NW3 2PF, UK

2 MRC Centre of Epidemiology for Child Health, UCL Institute of Child Health, University College London, London, UK

3 Homerton University Hospital NHS Foundation Trust, London, UK

4 Africa Centre for Health and Population Studies, University of KwaZulu-Natal, Durban, South Africa

5 Faculty of Medicine, Imperial College, London, UK

6 Health Protection Agency, Centre for Infections, London, UK

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BMC Medical Research Methodology 2012, 12:110  doi:10.1186/1471-2288-12-110

Published: 28 July 2012



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.


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).


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.

Data linkage; HIV; Pregnant women; Antiretroviral therapy; Cohort analysis; United Kingdom