A 25-year retrospective analysis of the American Society of Anesthesiologists physical status classification: did we “up-code” young obese patients when obesity was not yet considered a disease?

Reports of Original Investigations



The influence of obesity on anesthetic risk remains controversial, and obesity has only recently been specifically identified as a criterion by which a patient can be given a higher American Society of Anesthesiologists-physical status (ASA-PS) score. Nevertheless, we hypothesized that clinicians had assigned obese patients a greater ASA-PS score before obesity became an “official” criterion in 2015.


Basic demographic and physical details were collected on patients receiving anesthetics in the Virginia Commonwealth University Health System between 1986 and 2010. The risk ratio (RR) of “up-coding” ASA-PS classification assignments was calculated for patients of varying body mass index (BMI). We specifically focused on the subset of patients aged 20-29 yr in whom the medical sequelae of obesity would not yet likely be manifest.


Among a total of 194,698 patients, the percentage who were obese increased from 20% to 39% between 1986 and 2010. Obese patients of all ages were more likely than non-obese patients to be classified as ASA-PS II-IV rather than ASA-PS I. The RR and ratio of RR analyses indicated a consistent pattern of up-coding patients with greater BMI (contingency table Chi-square: P < 0.001). Most notably, relative to patients with a normal BMI, young obese patients aged 20-29 yr had an increased likelihood of up-coding in ASA-PS compared with obese patients in the older cohorts.


These findings suggest a consistent and temporally stable practice of up-coding obese patients despite this lack of explicit guidance. The ASA House of Delegates’ recent decision to specifically mention obesity reinforces long-existing practices regarding ASA-PS coding and will likely not degrade the validity of data sets collected before the change.

Vingt-cinq ans de rétrospective sur la classification du statut physique selon l’American Society of Anesthesiologists : avons-nous « gonflé » le codage des jeunes patients obèses alors que l’obésité n’était pas encore considérée comme une maladie?



L’influence de l’obésité sur le risque anesthésique reste controversée. L’obésité n’a été spécifiquement considérée comme un critère permettant d’attribuer un score de statut physique de l’American Society of Anesthesiologists (ASA-PS) plus élevé que récemment. Néanmoins, nous avons formulé l’hypothèse que les cliniciens avaient attribué aux patients obèses un score ASA-PS plus élevé avant même que l’obésité devienne un critère « officiel » en 2015.


Des caractéristiques démographiques et des détails physiques de base ont été collectés pour les patients recevant des anesthésiques entre 1986 et 2010 dans le Virginia Commonwealth University Health System. Le rapport de risque (RR) de « surcodage » des attributions de classification ASA-PS a été calculé pour des patients ayant divers indices de masse corporelle (IMC). Nous nous sommes concentrés sur le sous-groupe des patients âgés de 20 à 29 ans chez lesquels les conséquences médicales de l’obésité ne seraient vraisemblablement pas encore manifestes.


Sur un total de 194 698 patients, le pourcentage d’obèses a augmenté de 20 % à 39 % entre 1986 et 2010. Les patients obèses de tous âges étaient plus susceptibles d’être classés ASA-PS II à IV plutôt qu’ASA-PS I, par comparaison aux patients non obèses. Les analyses du RR et du ratio de RR ont indiqué un profil constant de surcodage des patients ayant un IMC plus élevé (test du chi-2 appliqué au tableau de contingence : P < 0,001). Par rapport aux patients ayant un IMC normal, il était particulièrement évident que les jeunes patients obèses (âgés de 20 à 29 ans) étaient plus susceptibles d’avoir un score ASA-PS surélevé par rapport aux patients obèses des groupes d’âge plus élevés.


Ces constatations suggèrent une pratique constante et stable dans le temps consistant à surcoder les patients obèses en dépit d’une absence de recommandations explicites. La décision récente de la House of Delegates de l’ASA de mentionner spécifiquement l’obésité renforce ces pratiques déjà anciennes concernant le codage de l’ASA-PS et n’altérera probablement pas la validité de l’ensemble de données collectés avant ce changement.


Conflicts of interest

None declared.

Editorial responsibility

This submission was handled by Dr. Hilary P. Grocott, Editor-in-Chief, Canadian Journal of Anesthesia.

Author contributions

Christopher Guerry helped design the study, conduct the study, analyze the data, and write the manuscript. He has seen the original study data, reviewed the analysis of the data, and approved the final manuscript. John F. Butterworth, IV, helped design the study, conduct the study, and write the manuscript. He has seen the original study data, reviewed the analysis of the data, approved the final manuscript, and is the author responsible for archiving the study files.


Departmental funding.


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Copyright information

© Canadian Anesthesiologists' Society 2018

Authors and Affiliations

  1. 1.Department of AnesthesiologyVirginia Commonwealth University School of Medicine, VCURichmondUSA

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