Interrater-Reliabilität der ASA-Klassifikation (In-ASK Studie)
Authors:   , Wagner Ananda Sophia 
Published: August 2022

Background The ASA-classification was established in 1941 by the anesthesiologists Saklad, Rovenstine, and Taylor and has been revised several times since, most recently in 2014 and 2020 with the addition of examplary diagnoses by the ASA. It provides a concise summary of the patient's preoperative health status based on six classes. The more severe a patient's preexisting conditions, the higher the class, and the more anesthesiologic attention should be given to the patient pre-, intra- and postoperatively. The aim of this study was to determine the reproducibility of that classification system based on interrater reliability, as well as to examine its predictive validity. Methods The present study included 684 general surgical patients >18 years of age (women 43%). An evaluation of all patients by three groups was performed: Surgeons, anesthesiologists, and a board consisting of a senior surgeon and a senior anesthesiologist. Interrater reliability between all three rater groups and between each two of the groups was calculated using kappa statistics (Fleiss' kappa). Furthermore, in a subgroup analysis, interrater reliability was examined in the evaluation of oncological patients and patients without malignancy, in multimorbid patients, and in geriatric patients. The influence of work experience – discerned by status of resident or attending physicians - on the degree of agreement was investigated. To test the predictive validity of the classification, a Spearman's correlation analysis between ASA-status and Clavien-Dindo complication classification was performed. Results and Assessment Interrater reliability between all raters (κ = 0.28, CI 0.21-0.34, p < 0.0001) and between each two of the rater groups showed sufficient agreement (surgeons vs. anesthesiologists: κ = 0.25, CI 0.19-0.30, surgeons vs. ASA board: κ = 0.21, CI 0.15-0.27, and anesthesiologists vs. ASA board: κ = 0.36, CI 0.30-0.43, each with p < 0.0001). The highest level of agreement was between anesthesiologists and the ASA board. Subgroup analysis comparing oncological and non-oncological patients yielded a lower degree of agreement in the group of patients with malignancy (κ = 0.18, CI 0.10-0.26 vs. κ = 0.38, CI 0.29-0.47, respectively, with p < 0.0001). The factors multimorbidity (κ = 0.19, CI 0.1-0.28, p = 0.00004) as well as a high patient age ≥ 75 years (κ = 0.19, CI 0.03-0.34, p = 0.02) were also associated with lower agreement. With increasing professional experience, the group of surgeons showed a higher agreement between raters and ASA board (residents κ = 0.20, CI 0.13-0.26, p < 0.0001, specialists κ = 0.32, CI 0.12-0.51, p = 0.002), in the group of anesthesiologists however there was no significant difference between young and experienced physicians (residents κ = 0.37, CI 0.29-0.44, specialists κ = 0.35, CI 0.24-0.46, respectively, p < 0.0001). There was a correlation between ASA-status and CDC in the present work (ϱ = 0.11, CI 0.04-0.19, p = 0.003). Conclusion The main advantage of the ASA-classification is its simplicity without the need for complex diagnostic procedures. It proves to be a valid tool to determine patients' preoperative health status and correlates with postoperative complications. A major drawback is its weak reproducibility due to its subjectivity and an its dependence on the examiner. Concomitant oncologic diseases, multimorbidity as well as geriatric patients are difficult to categorize and lead to uncertainty for the evaluators. They should be listed in the ASA sample catalog, which could facilitate reproducibility. As shown by relevant preceding studies, a modification of the ASA-classification would be desirable.