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Distribution of postpartum blood loss: modeling, estimation and application to clinical trials
BACKGROUND: The loss of large amounts of blood postpartum can lead to severe maternal morbidity and mortality. Understanding the nature of postpartum blood loss distribution is critical for the development of efficient analysis techniques when comparing treatments to prevent this event. When blood l...
Autores principales: | , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
BioMed Central
2018
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6280488/ https://www.ncbi.nlm.nih.gov/pubmed/30514326 http://dx.doi.org/10.1186/s12978-018-0641-1 |
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author | Carvalho, José Ferreira de Piaggio, Gilda Wojdyla, Daniel Widmer, Mariana Gülmezoglu, A. Metin |
author_facet | Carvalho, José Ferreira de Piaggio, Gilda Wojdyla, Daniel Widmer, Mariana Gülmezoglu, A. Metin |
author_sort | Carvalho, José Ferreira de |
collection | PubMed |
description | BACKGROUND: The loss of large amounts of blood postpartum can lead to severe maternal morbidity and mortality. Understanding the nature of postpartum blood loss distribution is critical for the development of efficient analysis techniques when comparing treatments to prevent this event. When blood loss is measured, resulting in a continuous volume measure, often this variable is categorized in classes, and reduced to an indicator of volume greater than a cutoff point. This reduction of volume to classes entails a substantial loss of information. As a consequence, very large trials are needed to assess clinically important differences between treatments to prevent postpartum haemorrhage. METHODS: The authors explore the nature of postpartum blood loss distribution, assuming that the physical properties of blood loss lead to a lognormal distribution. Data from four clinical trials and one observational study are used to confirm this empirically. Estimates of probabilities of postpartum haemorrhage events ‘blood loss greater than a cutoff point’ and relative risks are obtained from the fitted lognormal distributions. Confidence intervals for relative risk are obtained by bootstrap techniques. RESULTS: A variant of the lognormal distribution, the three-parameter lognormal distribution, showed an excellent fit to postpartum blood loss data of the four trials and the observational study. A measurement quality assessment showed that problems of digit preference and lower limit of detection were well handled by the lognormal fit. The analysis of postpartum haemorrhage events based on a lognormal distribution improved the efficiency of the estimates. Sample size calculation for a hypothetical future trial showed that the application of this procedure permits a reduction of sample size for treatment comparison. CONCLUSION: A variant of the lognormal distribution fitted very well postpartum blood loss data from different geographical areas, suggesting that the lognormal distribution might fit postpartum blood loss universally. An approach of analysis of postpartum haemorrhage events based on the lognormal distribution improves efficiency of estimates of probabilities and relative risk, and permits a reduction of sample size for treatment comparison. TRIAL REGISTRATION: This paper reports secondary analyses for trials registered at Australian New Zealand Clinical Trials Registry (ACTRN 12608000434392 and ACTRN12614000870651); and at clinicaltrials.gov (NCT00781066). ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12978-018-0641-1) contains supplementary material, which is available to authorized users. |
format | Online Article Text |
id | pubmed-6280488 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2018 |
publisher | BioMed Central |
record_format | MEDLINE/PubMed |
spelling | pubmed-62804882018-12-10 Distribution of postpartum blood loss: modeling, estimation and application to clinical trials Carvalho, José Ferreira de Piaggio, Gilda Wojdyla, Daniel Widmer, Mariana Gülmezoglu, A. Metin Reprod Health Research BACKGROUND: The loss of large amounts of blood postpartum can lead to severe maternal morbidity and mortality. Understanding the nature of postpartum blood loss distribution is critical for the development of efficient analysis techniques when comparing treatments to prevent this event. When blood loss is measured, resulting in a continuous volume measure, often this variable is categorized in classes, and reduced to an indicator of volume greater than a cutoff point. This reduction of volume to classes entails a substantial loss of information. As a consequence, very large trials are needed to assess clinically important differences between treatments to prevent postpartum haemorrhage. METHODS: The authors explore the nature of postpartum blood loss distribution, assuming that the physical properties of blood loss lead to a lognormal distribution. Data from four clinical trials and one observational study are used to confirm this empirically. Estimates of probabilities of postpartum haemorrhage events ‘blood loss greater than a cutoff point’ and relative risks are obtained from the fitted lognormal distributions. Confidence intervals for relative risk are obtained by bootstrap techniques. RESULTS: A variant of the lognormal distribution, the three-parameter lognormal distribution, showed an excellent fit to postpartum blood loss data of the four trials and the observational study. A measurement quality assessment showed that problems of digit preference and lower limit of detection were well handled by the lognormal fit. The analysis of postpartum haemorrhage events based on a lognormal distribution improved the efficiency of the estimates. Sample size calculation for a hypothetical future trial showed that the application of this procedure permits a reduction of sample size for treatment comparison. CONCLUSION: A variant of the lognormal distribution fitted very well postpartum blood loss data from different geographical areas, suggesting that the lognormal distribution might fit postpartum blood loss universally. An approach of analysis of postpartum haemorrhage events based on the lognormal distribution improves efficiency of estimates of probabilities and relative risk, and permits a reduction of sample size for treatment comparison. TRIAL REGISTRATION: This paper reports secondary analyses for trials registered at Australian New Zealand Clinical Trials Registry (ACTRN 12608000434392 and ACTRN12614000870651); and at clinicaltrials.gov (NCT00781066). ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12978-018-0641-1) contains supplementary material, which is available to authorized users. BioMed Central 2018-12-04 /pmc/articles/PMC6280488/ /pubmed/30514326 http://dx.doi.org/10.1186/s12978-018-0641-1 Text en © The Author(s). 2018 Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. |
spellingShingle | Research Carvalho, José Ferreira de Piaggio, Gilda Wojdyla, Daniel Widmer, Mariana Gülmezoglu, A. Metin Distribution of postpartum blood loss: modeling, estimation and application to clinical trials |
title | Distribution of postpartum blood loss: modeling, estimation and application to clinical trials |
title_full | Distribution of postpartum blood loss: modeling, estimation and application to clinical trials |
title_fullStr | Distribution of postpartum blood loss: modeling, estimation and application to clinical trials |
title_full_unstemmed | Distribution of postpartum blood loss: modeling, estimation and application to clinical trials |
title_short | Distribution of postpartum blood loss: modeling, estimation and application to clinical trials |
title_sort | distribution of postpartum blood loss: modeling, estimation and application to clinical trials |
topic | Research |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6280488/ https://www.ncbi.nlm.nih.gov/pubmed/30514326 http://dx.doi.org/10.1186/s12978-018-0641-1 |
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