This manuscript has been accepted for poster presentation at the 2016 ACS NSQIP Annual Conference in San Diego, CA.
The ASA physical classification score has a major impact on the observed/expected (O/E) mortality ratio in the NSQIP General Vascular Mortality Model. The difference in predicted mortality is greatest between ASAs 3 and 4. We hypothesized under-classified ASA scores significantly affect the O/E mortality.
We conducted a retrospective review of NSQIP essential surgery cases from January 2014 to December 2014 (n = 1264) with mortality sub-analysis (n = 33) at our institution. We recorded transfer and emergency status and independently calculated the ASA score for mortalities using published definitions. A random sample of 50 survivors and 10 emergency survivors were reviewed and ASA recalculated. We performed statistical modeling to simulate the effects of ASA misclassifications. Statistical analysis was performed using JMP 10 and SAS 9.4.
ASA was under-classified in 18.2% of mortalities, most commonly ASAs 3 and 4. Sixteen percent of ASA 3 survivors were misclassified, including 60% in the emergency subgroup (p < 0.05 vs. elective cases). Patients transferred from other institutions were more likely to be emergency cases than non-transferred patients (43.5 vs. 7.84%, p < 0.05). Transferred patients had a higher proportion of ASAs 3–5 vs. ASAs 1–2 compared with non-transfers (84.38 vs. 49.76%, p < 0.05) Simulation data showed ASA misclassification underestimated predicted mortality by 2.5 deaths on average.
ASA misclassification significantly impacts O/E mortality. With accurate ASA classification, observed mortality would not have exceeded expected mortality in our institution. Education regarding the impact of ASA scoring is critical to ensure accurate O/E mortality data at hospitals using NSQIP to assess surgical quality.
Davenport DL, Bowe EA, Henderson WG, Khuri SF, Mentzer RM Jr. National Surgical Quality Improvement Program (NSQIP) risk factors can be used to validate American Society of Anesthesiologists Physical Status Classification (ASA PS) levels. Ann Surg. 2006;243(5):636–41. discussion 641-634 CrossRefPubMedPubMedCentral
Davenport DL, Henderson WG, Khuri SF, Mentzer RM Jr. Preoperative risk factors and surgical complexity are more predictive of costs than postoperative complications: a case study using the National Surgical Quality Improvement Program (NSQIP) database. Ann Surg. 2005;242(4):463–8. discussion 468-471 PubMedPubMedCentral
Hyder JA, Reznor G, Wakeam E, Nguyen LL, Lipsitz SR, Havens JM. Risk prediction accuracy differs for emergency versus elective cases in the ACS-NSQIP. Ann Surg. 2015;264(6):959-65.
- Impact of ASA score misclassification on NSQIP predicted mortality: a retrospective analysis
Sumeet V. Jain
Robert N. Cooney
- BioMed Central
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