ArticlesValidation of the paediatric logistic organ dysfunction (PELOD) score: prospective, observational, multicentre study
Introduction
Death is thought by many intensive care consultants to be the most reliable endpoint for clinical trials in intensive care units. However, with death as the primary outcome measure, the low death rate in paediatric intensive care units (about 6%1, 2, 3 vs >20% in adult intensive care units4, 5) increases the sample size required to complete a clinical trial, which reduces the feasibility of doing clinical trials in such units. A surrogate outcome can be substituted (or at least added) to a gold standard such as death rate, if its relation to the gold standard is very good, and if the prevalence of what it measures is substantially greater than that of the gold standard. Multiple organ dysfunction syndrome is more frequent than death in paediatric intensive care units—the rate ranges from 11% to 27%6, 7, 8, 9 Thus, a score that could be used to estimate the severity of multiple organ dysfunction syndrome could be an additional outcome measure to death in critically ill patients.10 The difference in rate should significantly reduce the sample size required to complete a clinical trial if multiple organ dysfunction syndrome is chosen as the primary outcome measure rather than death. Three multiple organ dysfunction syndrome scores have been validated in adults for this purpose,4, 5, 11 but none in children. In a prospective, multicentre study, we developed a paediatric multiple-organ dysfunction syndrome score, the paediatric logistic organ dysfunction (PELOD) score.12 This score was developed against mortality as in all such studies in adults. In this study, we aimed to validate the PELOD score, which is based on the most abnormal values of variables measured during the entire paediatric intensive care unit stay; and to estimate the validity of the PELOD score when recorded daily (dPELOD).
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Participants
We prospectively included all consecutive patients admitted to seven multidisciplinary, tertiary-care paediatric intensive care units of university-affiliated hospitals (two French, three Canadian, and two Swiss). Exclusion criteria were age 18 years or older, premature, pregnant, length of stay in unit less than 4 h, admission in a state of continuous cardiopulmonary resuscitation without achieving stable vital signs for at least 2 h, transfer to another paediatric intensive care unit, and
Statistical analyses
An estimated 1422 patients (203 patients or 14 deaths by centre) were needed for 80% power with significance at 5% for an estimated mortality rate of 7% and relative risk worth detecting at 1·35 (PELOD odds ratio=0·30). We assessed interobserver reliability of data collection by checking a random selection of 3% of included patients and using the κ statistic for each organ dysfunction and the intraclass correlation coefficient for PELOD and dPELOD scores to estimate agreement.
The dependent
Results
Between September, 1998 and February, 2000, there were 2021 consecutive admissions. 215 patients were excluded for the following reasons: incomplete records (13); still cared for in paediatric intensive care units (two); palliative care (two); and exclusion criteria (in order listed in methods) 12, 55, 0, 13, 0, one, and 117, respectively. Thus, we included 1806 patients. Median length of study period in the units was 5 (IQR 4–6) months. The case-fatality rate was 6·4% (115 deaths). Table 2
Discussion
Our results validate the PELOD score. We have also validated the dPELOD score for the first 5 days of stay in paediatric intensive care units, which should enable increased sensitivity in assessment of changes in a patient's condition.
A scoring system should have construct and content validity. It must be able to be reproduced over time and across geographic and methodological boundaries and be accurate (calibration and discrimination) and clinically meaningful.14 The construct validity of the
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