We concur with Quintairos et al (1) that benchmarking mortality outcome using standardized mortality ratios (SMRs) in coronavirus disease 2019 (COVID-19) patients is presently challenging, since evidence points to disproportionate severity-adjusted mortality (2, 3). Although the influx of COVID-19 patients would be expected to increase overall hospital SMR at an institution, important questions are whether SMR is also now elevated in non-COVID patients and how SMR is changing during the pandemic.
A preliminary look at 38 hospitals consistently contributing Acute Physiology and Chronic Health Evaluation (APACHE) data during the pandemic (Fig. 1) suggests that overall SMR (top line) has increased concurrently with each “wave” of COVID-19 as tracked by the Centers for Disease Control and Prevention (4). An increase in SMR occurs but is attenuated when COVID patients are removed from analysis (bottom line). SMR in COVID patients alone (not shown) ranged from 1.27 to 1.96 using “viral pneumonia” coefficients for APACHE IVb risk adjustment.
Figure 1.
Standardized hospital mortality at 38 hospitals contributing Acute Physiology and Chronic Health Evaluation data from January 2020 through May 2021. The upper line displays standardized mortality rate (SMR) for all patients (coronavirus disease [COVID] included) and the lower line with COVID patients removed. Points with an asterisk are statistically different at p < 0.05.
In this group of hospitals, to whom we are grateful for supplying data, prepandemic SMR was better than expected and follows a slight downward trajectory. Beginning in April 2020, worsening outcomes are observed overall, but not when COVID patients are removed. By the second wave (July 2020), the SMR is increasing for non-COVID patients. During the third wave (November 2020–January 2021), SMR exceeds 1.0 for non-COVID patients. Total patients per month are greater than 5,000, and the SMR difference becomes significant at p < 0.05 during each wave.
We hypothesize that altered triage decisions, resource and staffing constraints, and case mix differences (including average age) may all play a role in non-COVID patients. The recent return of SMR to prepandemic values is encouraging, but we await data from the fourth wave presently underway to see if a similar effect on non-COVID patients occurs with higher COVID patient volume.
Although we plan to recalibrate APACHE predictions to provide a proper coefficient for COVID patients, such customization may presently prove unstable due to regional pandemic surges, evolving therapy and emergence of new variants. Until models such as APACHE can be accurately updated, healthcare providers should be aware that SMR and length-of-stay benchmarks for ICU patients might periodically be significantly elevated above pre-COVID-19 values due to pandemic effects.
Footnotes
Dr. Higgins, Ms. Freeseman-Friedman, Ms. Henson, and Mr. Ringle received funding from Cerner Corporation.
REFERENCES
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