Neuroanesthesia and Intensive Care Limited ability of SOFA and MOD scores to discriminate outcome: a prospective evaluation in 1,436 patients

PurposeThe multiple organ dysfunction (MOD) score and sequential organ failure assessment (SOFA) score are measures of organ dysfunction and have been validated based on the association of these scores with mortality. We sought to compare the performance of the SOFA and MOD scores in a large cohort of consecutive multisystem intensive care unit (ICU) patients.MethodsProspective automated daily measurements of MOD and SOFA scores were performed in 1,436 patients admitted to a multisystem ICU in the Calgary Health Region over a one-year period. Logistic regression modeling techniques were used to describe the association of SOFA and MODS with mortality. Receiver operator characteristic (ROC) curves were used to assess the model’s discriminatory ability.ResultsFor ICU and hospital mortality, there was very little practical difference between the SOFA and MOD scores in their ability to discriminate outcome as determined by the area under the ROC. However, compared to previous literature, the discriminatory ability of both scores in this population was weak. As well, the calibration of the models was poor for both scores. The SOFA cardiovascular component score performed better than the MOD cardiovascular component score in the discrimination of both ICU and hospital mortality.ConclusionsSOFA and MOD scores had only a modest ability to discriminate between survivors and non-survivors. These results question the appropriateness of using organ dysfunction scores as a ’surrogate’ for mortality in clinical trials and suggest further work is necessary to better understand the temporal relationship and course of organ failure with mortality.RésuméObjectifLe score de défaillance multiviscérale (DMV) et le score de SOFA (Sequential Organ Failure Assessment) mesurent la dysfonction organique et ont été validés sur leur association avec la mortalité. Nous avons comparé leur performance chez des patients successivement admis à l’unité des soins intensifs (USI) pour une atteinte multiviscérale. Méthode : Les mesures quotidiennes, prospectives et automatisés des scores de DMV et de SOFA ont été faites chez 1 436 patients admis à une USI multiviscéraux dans la région de Calgary pendant une année. Une modélisation de régression logistique a servi à décrire l’association des scores de SOFA et de DMV à la mortalité. La capacité discriminatoire du modèle a été évaluée par les courbes ROC (Receiver Operator Characteristic).RésultatsConcernant la mortalité à l’USI et à l’hôpital, les scores de SOFA et de DMV présentaient une très petite différence pratique de capacité à distinguer les résultats comme l’a montré l’aire sous la courbe ROC. Comparée aux données des publications antérieures, la capacité discriminatoire des deux scores était faible pour la population évaluée. Aussi, le calibrage des modèles était pauvre pour les deux scores. Le score de la composante cardiovasculaire du SOFA a présenté une meilleure performance que celui de la DMV quant à la détermination de la mortalité à l’USI et à l’hôpital.ConclusionLes scores de SOFA et de DMV n’ont qu’une faible capacité à distinguer les patients qui vont survivre ou non. Cela remet en question la pertinence d’utiliser des scores de dysfonction organique comme «substitut» à la mortalité dans les essais cliniques et incite à chercher à découvrir la relation temporelle entre l’évolution de la défaillance organique et la mortalité.

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