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

Hill, Teresa; Bansi, Loveleen; Sabin, Caroline; Phillips, Andrew; Dunn, David; Anderson, Jane; Easterbrook, Philippa; Fisher, Martin; Gazzard, Brian; Gilson, Richard; Johnson, Margaret; Leen, Clifford; Orkin, Chloe; Schwenk, Achim; Walsh, John; Winston, Alan; Babiker, Abdel; Delpech, Valerie; UK Collaborative HIV Cohort (UK CHIC) Study Group,

doi:10.1016/j.jclinepi.2009.12.007

« Previous Next »Journal of Clinical Epidemiology
Volume 63, Issue 10 , Pages 1101-1109, October 2010

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

Teresa Hill
- Research Department of Infection and Population Health, UCL Medical School, London, UK
- Corresponding author. Research Department of Infection and Population Health, UCL Medical School, University College London, London NW3 2PF, UK. Tel.: +44-0-20-7830-2239 ext. 36762; fax: +44-0-20-7794-1224.
Loveleen Bansi
- Research Department of Infection and Population Health, UCL Medical School, London, UK
Caroline Sabin
- Research Department of Infection and Population Health, UCL Medical School, London, UK
Andrew Phillips
- Research Department of Infection and Population Health, UCL Medical School, London, UK
David Dunn
- MRC Clinical Trials Unit, London, UK
Jane Anderson
- Homerton University Hospital NHS Trust, London, UK
Philippa Easterbrook
- King's College Hospital NHS Trust, London, UK
Martin Fisher
- Brighton and Sussex University Hospitals NHS Trust, Brighton, UK
Brian Gazzard
- Chelsea and Westminster NHS Trust, London, UK
Richard Gilson
- Mortimer Market Centre, UCL Medical School, London, UK
Margaret Johnson
- Royal Free NHS Trust and UCL Medical School, London, UK
Clifford Leen
- The Lothian University Hospitals NHS Trust, Edinburgh, UK
Chloe Orkin
- Barts and The London NHS Trust, London, UK
Achim Schwenk
- North Middlesex University Hospital NHS Trust, London, UK
John Walsh
- Imperial College Healthcare NHS Trust, London, UK
Alan Winston
- Imperial College Healthcare NHS Trust, London, UK
Abdel Babiker
- MRC Clinical Trials Unit, London, UK
Valerie Delpech
- Health Protection Agency Centre for Infections London (HPA CfI) London, UK
UK Collaborative HIV Cohort (UK CHIC) Study Group

Accepted 4 December 2009. published online 29 March 2010.

Abstract

Objective

To ascertain the degree of loss to follow-up in a cohort and to identify its predictors.

Study Design and Setting

Human immunodeficiency virus (HIV)–infected individuals without CD4 cell counts for a year or more were defined as potentially lost to follow-up (LFU). Multivariable Poisson regression models identified the risk factors for potential LFU. Multivariable logistic regression models compared demographic and clinical characteristics of those who returned for care and those permanently LFU.

Results

Of 16,595 patients under follow-up, 43.6% were potentially LFU at least once. Of these, 39.8% were considered permanently LFU and 60.2% were seen again after 1 year. Of 9,766 episodes when patients were potentially LFU, 59% resulted in the patient returning for care at the same clinic or at a different clinic. Compared with those permanently LFU, patients returning were more likely to have started highly active antiretroviral therapy, to have higher CD4 counts and viral loads, to be younger, and to have had more CD4 tests before LFU. They were less likely to have had a previous episode of potential LFU.

Conclusions

A substantial proportion of patients in the UK Collaborative HIV Cohort study are potentially LFU. Data linkage identifies patients returning for care at different centers. Recognition of factors associated with LFU may help reduce this important source of bias in observational databases.

Keywords: Cohort, HIV, Loss to follow-up, Data linkage, Follow-up, Risk factors