ASA Physical Status Score: has its time passed?
AbstractThe American Society of Anaesthesiologists’ Physical Status Score (ASAPS) was originally developed in 1941 by three anesthesiologists: MeyerSaklad, Emery Rovenstine and Ivan Taylor.1 They did this in response to a request from the ASA to classify operative risk, so as to be able to compare surgical outcomes – essentially, they were asked to develop a risk-adjustment model. They concluded that it was not possible to do this, owing to the myriad of interactions there would be between the patient’s health and the surgical procedure undertaken (their deliberations took place during the second world war, preceding Turing’s first electronic stored program digital computer and the development of logistic regression modelling in the 1950s, both of which would ideally have been required to address this statistical issue). Therefore, they resolved to determine a classification system for the patients’ physical status only, and did so using a 6-grade system. The first four grades approximated to the current ASA 1 to 4 definitions; their original classes 5 and 6 were used to describe emergency patients who were otherwise ASA 1 or 2 (Class 5) or 3 or 4 (Class 6). When the ASA published an updated version in 1963, they dropped the original classes 5 and 6 in favour of adding the suffix ‘E’ to ASA 1 to 4 grades for emergency cases; they then added the current definition of ASA 5 (moribund patient likely to die without surgery); and later ASA 6 (brain-stem dead organ donor). The ASA-PS has stood the test of time, providing the most commonly used language to describe patient risk; however, as the study led by Dr Singaram and published in this issue of the SAJAA has found, there can be substantial inter-rater variability in estimates of the ASA-PS grade between clinicians. This is not the first study to find this problem – in other countries, they have used similar methodology to Singaram et al, providing simulated scenarios to anaesthetists.2,3 However, at least one real-world evaluation has also compared ASA grading in the same patient but two different clinical settings (the preoperative assessment clinic and the operating theatre) and again found substantial variation in measurement.4 These repeated findings required us to consider two questions – what are the implications and what are the solutions?
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