Prevention of postpartum haemorrhage: a distributional approach for analysis
- PDF / 822,312 Bytes
- 8 Pages / 595.276 x 790.866 pts Page_size
- 20 Downloads / 188 Views
RESEARCH
Open Access
Prevention of postpartum haemorrhage: a distributional approach for analysis Gilda Piaggio1*, José Ferreira de Carvalho2 and Fernando Althabe3 From 2nd International Conference on Maternal and Newborn Health: Translating Research Evidence to Practice Belagavi, India. 26-27 March 2018
Abstract Background: There is empirical evidence that measured postpartum blood loss has a lognormal distribution. This feature can be used to analyze events of the type ‘blood loss greater than a certain cutoff point’ using a lognormal approach, which takes into account all the quantitative observations, as opposed to dichotomizing the variable blood loss volume into two categories. This lognormal approach uses all the information contained in the data and is expected to provide more efficient estimates of proportions and relative risk when comparing treatments to prevent postpartum haemorrhage. As a consequence, sample size can be reduced in clinical trials, while keeping the statistical precision requirements. Methods: The authors illustrate how a lognormal approach can be used in this situation, using data from a clinical trial and the event ‘blood loss greater than 1000 mL’. Results: Estimates of the proportions of this event for each treatment, and relative risks obtained with this method are presented and compared with the standard estimates obtained by dichotomizing measured blood loss volume. An example of how the blood loss distributions of two treatments can be compared is also presented. Different scenarios of the sample size needed to compare two treatments or interventions are presented to illustrate how with the lognormal approach the size of a clinical trial can be reduced. Conclusions: A distributional approach for postpartum blood loss using the lognormal distribution fitted to the data results in more precise estimates of risks of events and relative risks, compared to the use of binomial proportions of events. It also results in reduced required sample size for clinical trials. Trial registration: This paper reports a secondary analysis for a trial that was registered at clinicaltrials.gov (NCT00781066). Keywords: Postpartum blood loss, Postpartum haemorrhage, Severe postpartum haemorrhage, Lognormal distribution
Background The development of an adequate statistical analysis technique to analyze a continuous variable depends on the knowledge of its distribution. Many variables in biology and medicine follow the normal distribution and standard statistical techniques can be applied to compare means. However, when the distribution is not normal, the standard statistical techniques are no longer appropriate and a transformation is often used to normalize * Correspondence: [email protected] 1 Statistika Consultoria, Campinas, São Paulo, Brazil Full list of author information is available at the end of the article
the distribution. This has been the case with postpartum blood loss, for which a logarithmic transformation has been used to compare medians, [1] based on the observation that th
Data Loading...
