Correcting mortality for loss to follow-up: A nomogram applied to antiretroviral treatment programmes in sub-Saharan Africa

Matthias Egger, Ben D. Spycher, John Sidle, Ralf Weigel, Elvin H. Geng, Matthew P. Fox, Patrick MacPhail, Gilles van Cutsem, Eugène Messou, Robin Wood, Denis Nash, Margaret Pascoe, Diana Dickinson, Jean François Etard, James A. McIntyre, Martin W.G. Brinkhof

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Abstract

Background: The World Health Organization estimates that in sub-Saharan Africa about 4 million HIV-infected patients had started antiretroviral therapy (ART) by the end of 2008. Loss of patients to follow-up and care is an important problem for treatment programmes in this region. As mortality is high in these patients compared to patients remaining in care, ART programmes with high rates of loss to follow-up may substantially underestimate mortality of all patients starting ART. Methods and Findings: We developed a nomogram to correct mortality estimates for loss to follow-up, based on the fact that mortality of all patients starting ART in a treatment programme is a weighted average of mortality among patients lost to follow-up and patients remaining in care. The nomogram gives a correction factor based on the percentage of patients lost to follow-up at a given point in time, and the estimated ratio of mortality between patients lost and not lost to follow-up. The mortality observed among patients retained in care is then multiplied by the correction factor to obtain an estimate of programme-level mortality that takes all deaths into account. A web calculator directly calculates the corrected, programme-level mortality with 95% confidence intervals (CIs). We applied the method to 11 ART programmes in sub-Saharan Africa. Patients retained in care had a mortality at 1 year of 1.4% to 12.0%; loss to follow-up ranged from 2.8% to 28.7%; and the correction factor from 1.2 to 8.0. The absolute difference between uncorrected and corrected mortality at 1 year ranged from 1.6% to 9.8%, and was above 5% in four programmes. The largest difference in mortality was in a programme with 28.7% of patients lost to follow-up at 1 year. Conclusions: The amount of bias in mortality estimates can be large in ART programmes with substantial loss to follow-up. Programmes should routinely report mortality among patients retained in care and the proportion of patients lost. A simple nomogram can then be used to estimate mortality among all patients who started ART, for a range of plausible mortality rates among patients lost to follow-up.

Original languageEnglish (US)
Article numbere1000390
JournalPLoS Medicine
Volume8
Issue number1
DOIs
StatePublished - Feb 21 2011

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Nomograms
Africa South of the Sahara
Mortality
Lost to Follow-Up
Therapeutics
Aftercare

ASJC Scopus subject areas

  • Medicine(all)

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Correcting mortality for loss to follow-up : A nomogram applied to antiretroviral treatment programmes in sub-Saharan Africa. / Egger, Matthias; Spycher, Ben D.; Sidle, John; Weigel, Ralf; Geng, Elvin H.; Fox, Matthew P.; MacPhail, Patrick; van Cutsem, Gilles; Messou, Eugène; Wood, Robin; Nash, Denis; Pascoe, Margaret; Dickinson, Diana; Etard, Jean François; McIntyre, James A.; Brinkhof, Martin W.G.

In: PLoS Medicine, Vol. 8, No. 1, e1000390, 21.02.2011.

Research output: Contribution to journalArticle

Egger, M, Spycher, BD, Sidle, J, Weigel, R, Geng, EH, Fox, MP, MacPhail, P, van Cutsem, G, Messou, E, Wood, R, Nash, D, Pascoe, M, Dickinson, D, Etard, JF, McIntyre, JA & Brinkhof, MWG 2011, 'Correcting mortality for loss to follow-up: A nomogram applied to antiretroviral treatment programmes in sub-Saharan Africa', PLoS Medicine, vol. 8, no. 1, e1000390. https://doi.org/10.1371/journal.pmed.1000390
Egger, Matthias ; Spycher, Ben D. ; Sidle, John ; Weigel, Ralf ; Geng, Elvin H. ; Fox, Matthew P. ; MacPhail, Patrick ; van Cutsem, Gilles ; Messou, Eugène ; Wood, Robin ; Nash, Denis ; Pascoe, Margaret ; Dickinson, Diana ; Etard, Jean François ; McIntyre, James A. ; Brinkhof, Martin W.G. / Correcting mortality for loss to follow-up : A nomogram applied to antiretroviral treatment programmes in sub-Saharan Africa. In: PLoS Medicine. 2011 ; Vol. 8, No. 1.
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abstract = "Background: The World Health Organization estimates that in sub-Saharan Africa about 4 million HIV-infected patients had started antiretroviral therapy (ART) by the end of 2008. Loss of patients to follow-up and care is an important problem for treatment programmes in this region. As mortality is high in these patients compared to patients remaining in care, ART programmes with high rates of loss to follow-up may substantially underestimate mortality of all patients starting ART. Methods and Findings: We developed a nomogram to correct mortality estimates for loss to follow-up, based on the fact that mortality of all patients starting ART in a treatment programme is a weighted average of mortality among patients lost to follow-up and patients remaining in care. The nomogram gives a correction factor based on the percentage of patients lost to follow-up at a given point in time, and the estimated ratio of mortality between patients lost and not lost to follow-up. The mortality observed among patients retained in care is then multiplied by the correction factor to obtain an estimate of programme-level mortality that takes all deaths into account. A web calculator directly calculates the corrected, programme-level mortality with 95{\%} confidence intervals (CIs). We applied the method to 11 ART programmes in sub-Saharan Africa. Patients retained in care had a mortality at 1 year of 1.4{\%} to 12.0{\%}; loss to follow-up ranged from 2.8{\%} to 28.7{\%}; and the correction factor from 1.2 to 8.0. The absolute difference between uncorrected and corrected mortality at 1 year ranged from 1.6{\%} to 9.8{\%}, and was above 5{\%} in four programmes. The largest difference in mortality was in a programme with 28.7{\%} of patients lost to follow-up at 1 year. Conclusions: The amount of bias in mortality estimates can be large in ART programmes with substantial loss to follow-up. Programmes should routinely report mortality among patients retained in care and the proportion of patients lost. A simple nomogram can then be used to estimate mortality among all patients who started ART, for a range of plausible mortality rates among patients lost to follow-up.",
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T2 - A nomogram applied to antiretroviral treatment programmes in sub-Saharan Africa

AU - Egger, Matthias

AU - Spycher, Ben D.

AU - Sidle, John

AU - Weigel, Ralf

AU - Geng, Elvin H.

AU - Fox, Matthew P.

AU - MacPhail, Patrick

AU - van Cutsem, Gilles

AU - Messou, Eugène

AU - Wood, Robin

AU - Nash, Denis

AU - Pascoe, Margaret

AU - Dickinson, Diana

AU - Etard, Jean François

AU - McIntyre, James A.

AU - Brinkhof, Martin W.G.

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