TY - JOUR
T1 - A comparative analysis of the respiratory subscore of the sequential organ failure assessment scoring system
AU - Schenck, Edward J.
AU - Hoffman, Katherine L.
AU - Oromendia, Clara
AU - Sanchez, Elizabeth
AU - Finkelsztein, Eli J.
AU - Hong, Kyung Sook
AU - Kabariti, Joseph
AU - Torres, Lisa K.
AU - Harrington, John S.
AU - Siempos, Ilias I.
AU - Choi, Augustine M.K.
AU - Campion, Thomas R.
N1 - Publisher Copyright:
© 2021 by the American Thoracic Society
PY - 2021/11
Y1 - 2021/11
N2 - Rationale: The Sequential Organ Failure Assessment (SOFA) tool is a commonly used measure of illness severity. Calculation of the respiratory subscore of SOFA is frequently limited by missing arterial oxygen pressure (PaO2) data. Although missing PaO2 data are commonly replaced with normal values, the performance of different methods of substituting PaO2 for SOFA calculation is unclear. Objectives: The study objective was to compare the performance of different substitution strategies for missing PaO2 data for SOFA score calculation. Methods: This retrospective cohort study was performed using the Weill Cornell Critical Care Database for Advanced Research from a tertiary care hospital in the United States. All adult patients admitted to an intensive care unit (ICU) from 2011 to 2019 with an available respiratory SOFA score were included. We analyzed the availability of the PaO2/fraction of inspired oxygen (FIO2) ratio on the first day of ICU admission. In those without a PaO2/FIO2 ratio available, the ratio of oxygen saturation as measured by pulse oximetry to FIO2 was used to calculate a respiratory SOFA subscore according to four methods (linear substitution [Rice], nonlinear substitution [Severinghaus], modified respiratory SOFA, and multiple imputation by chained equations [MICE]) as well as the missing-as-normal technique. We then compared how well the different total SOFA scores discriminated in-hospital mortality. We performed several subgroup and sensitivity analyses. Results: We identified 35,260 unique visits, of which 9,172 included predominant respiratory failure. PaO2 data were available for 14,939 (47%). The area under the receiver operating characteristic curve for each substitution technique for discriminating in-hospital mortality was higher than that for the missing-as-normal technique (0.78 [0.77–0.79]) in all analyses (modified, 0.80 [0.79–0.81]; Rice, 0.80 [0.79–0.81]; Severinghaus, 0.80 [0.79–0.81]; and MICE, 0.80 [0.79–0.81]) (P, 0.01). Each substitution method had a higher accuracy for discriminating in-hospital mortality (MICE, 0.67; Rice, 0.67; modified, 0.66; and Severinghaus, 0.66) than the missing-as-normal technique. Model calibration for in-hospital mortality was less precise for the missing-as-normal technique than for the other substitution techniques at the lower range of SOFA and among the subgroups. Conclusions: Using physiologic and statistical substitution methods improved the total SOFA score’s ability to discriminate mortality compared with the missing-as-normal technique. Treating missing data as normal may result in underreporting the severity of illness compared with using substitution. The simplicity of a direct oxygen saturation as measured by pulse oximetry/FIO2 ratio–modified SOFA technique makes it an attractive choice for electronic health record–based research. This knowledge can inform comparisons of severity of illness across studies that used different techniques.
AB - Rationale: The Sequential Organ Failure Assessment (SOFA) tool is a commonly used measure of illness severity. Calculation of the respiratory subscore of SOFA is frequently limited by missing arterial oxygen pressure (PaO2) data. Although missing PaO2 data are commonly replaced with normal values, the performance of different methods of substituting PaO2 for SOFA calculation is unclear. Objectives: The study objective was to compare the performance of different substitution strategies for missing PaO2 data for SOFA score calculation. Methods: This retrospective cohort study was performed using the Weill Cornell Critical Care Database for Advanced Research from a tertiary care hospital in the United States. All adult patients admitted to an intensive care unit (ICU) from 2011 to 2019 with an available respiratory SOFA score were included. We analyzed the availability of the PaO2/fraction of inspired oxygen (FIO2) ratio on the first day of ICU admission. In those without a PaO2/FIO2 ratio available, the ratio of oxygen saturation as measured by pulse oximetry to FIO2 was used to calculate a respiratory SOFA subscore according to four methods (linear substitution [Rice], nonlinear substitution [Severinghaus], modified respiratory SOFA, and multiple imputation by chained equations [MICE]) as well as the missing-as-normal technique. We then compared how well the different total SOFA scores discriminated in-hospital mortality. We performed several subgroup and sensitivity analyses. Results: We identified 35,260 unique visits, of which 9,172 included predominant respiratory failure. PaO2 data were available for 14,939 (47%). The area under the receiver operating characteristic curve for each substitution technique for discriminating in-hospital mortality was higher than that for the missing-as-normal technique (0.78 [0.77–0.79]) in all analyses (modified, 0.80 [0.79–0.81]; Rice, 0.80 [0.79–0.81]; Severinghaus, 0.80 [0.79–0.81]; and MICE, 0.80 [0.79–0.81]) (P, 0.01). Each substitution method had a higher accuracy for discriminating in-hospital mortality (MICE, 0.67; Rice, 0.67; modified, 0.66; and Severinghaus, 0.66) than the missing-as-normal technique. Model calibration for in-hospital mortality was less precise for the missing-as-normal technique than for the other substitution techniques at the lower range of SOFA and among the subgroups. Conclusions: Using physiologic and statistical substitution methods improved the total SOFA score’s ability to discriminate mortality compared with the missing-as-normal technique. Treating missing data as normal may result in underreporting the severity of illness compared with using substitution. The simplicity of a direct oxygen saturation as measured by pulse oximetry/FIO2 ratio–modified SOFA technique makes it an attractive choice for electronic health record–based research. This knowledge can inform comparisons of severity of illness across studies that used different techniques.
KW - Imputation
KW - Organ dysfunction
KW - Respiratory failure
KW - Sequential Organ Failure Assessment score
KW - Survival
UR - http://www.scopus.com/inward/record.url?scp=85118480478&partnerID=8YFLogxK
U2 - 10.1513/AnnalsATS.202004-399OC
DO - 10.1513/AnnalsATS.202004-399OC
M3 - Article
C2 - 33760709
AN - SCOPUS:85118480478
SN - 2329-6933
VL - 18
SP - 1849
EP - 1860
JO - Annals of the American Thoracic Society
JF - Annals of the American Thoracic Society
IS - 11
ER -