The ASA Physical Status Classification System is an important tool for anesthesia providers when evaluating patient safety ahead of a procedure requiring anesthesia. The purpose of the system is to assess and communicate a patient’s pre-anesthesia medical co-morbidities (1). It is widely used by both anesthesiologists and CRNAs, as well as surgeons. Research has found that patient designations are indeed associated with perioperative risk, though it does not alone offer a complete picture (1,2). However, it has several limitations, with one major limitation being that individual providers often do not agree on the status designation for a patient (3-5). Inconsistencies ASA status classifications between anesthesiologists and surgeons have been recently identified as having clinical significance in terms of patient outcomes (3,5). 

The classification system defines six categories of patients, with level 1 being a normal, healthy individual and level 5 being an individual who is immediately at risk of death and requires surgery to have a chance of survival. (Level 6 designates brain-dead patient undergoing an organ donation procedure.) It was first developed over 60 years ago and has since been revised for clarity (1). 

One concern with the previous version of the ASA physical status definitions was the heterogeneity in assignments. Given the system’s intended role in broadly evaluating a patient’s risk-increasing comorbidities and communicating the holistic evaluation in an easily understandable format, the finding that different anesthesia providers may arrive at different conclusions poses a problem (3). 

In 2014, the ASA added examples to the official definitions – for adults, pediatric patients, and obstetric patients. Research then found that these examples significantly improved accuracy for both anesthesia providers and non-anesthesia healthcare providers. Furthermore, non-anesthesia providers, who were in fields that commonly use the classification system, saw greater improvement (3). 

However, some inconsistencies remain. Real patients are more complex than clinical scenarios, which likely contributes to disagreements in classification. A study published in 2018 examined ASA physical status designations by providers in three different departments at one institution. Patients were assessed pre-operatively by an internal medicine provider, a provider in the pre-anesthesia team, and the anesthesia provider. Researchers identified significant inter-rater variability, but also found that the anesthesia-run pre-anesthesia team and the anesthesia providers were most in tune (4). 

Most recently, Kwa et al. found that inconsistency between the anesthesiologist and surgeon was associated with poorer patient outcomes after surgery. Over 46,000 elective surgery patients were included in a retrospective review. Overall, there was moderate concordance between surgeons and anesthesiologists on ASA physical status. Patients for whom the assigned designations were more different were more likely to die within 30 days, die within 1 year, and need ICU admission. Discordant ASA classes may be a red flag for missed comorbidities by a member of the surgical team, however, further research is needed to identify common reasons behind this phenomenon (5). 

Increasing standardization of ASA designations is likely to improve patient safety – providers may more accurately assess patients’ physical status and associated risk prior to the procedure, and surgeons and anesthesiologists may be better able to work together to optimize the outcome of the procedure. This system has been shown to reliably predict the risk of complications associated with surgery by some research, while other established methods of predicting risk often integrate the ASA designation into their calculations (2,6,7). 

References 

1. “​ASA Physical Status Classification System.” American Society of Anesthesiologists. 2020. https://www.asahq.org/standards-and-guidelines/asa-physical-status-classification-system 

2. Hackett, N. J. et al. ASA class is a reliable independent predictor of medical complications and mortality following surgery. International Journal of Surgery. 2015;18:184-190. https://doi.org/10.1016/j.ijsu.2015.04.079  

3. Hurwitz, E. E. et al. Adding Examples to the ASA-Physical Status Classification Improves Correct Assignment to Patients. Anesthesiology. 2017;126:614–622 https://doi.org/10.1097/ALN.0000000000001541 

4. Knuf, K. M. et al. Clinical agreement in the American Society of Anesthesiologists physical status classification. Perioperative Medicine. 2018;7. https://doi.org/10.1186/s13741-018-0094-7 

5. Kwa, C. X. W. et al. Discordant American Society of Anesthesiologists Physical Status Classification between anesthesiologists and surgeons and its correlation with adverse patient outcomes. Scientific Reports. 2022;12. https://doi.org/10.1038/s41598-022-10736-5 

6. Protopapa, K. L. et al. Development and validation of the Surgical Outcome Risk Tool (SORT). British Journal of Surgery. 2014;101(13): 1774–1783. https://doi.org/10.1002/bjs.9638 

7. Davenport, D. L., et al. National Surgical Quality Improvement Program (NSQIP) Risk Factors Can Be Used to Validate American Society of Anesthesiologists Physical Status Classification (ASA PS) Levels. Annals of Surgery. 2006;243(5):636–644. https://doi.org10.1097/01.sla.0000216508