Accuracy of the Sequential Organ Failure Assessment Score for In-Hospital Mortality by Race and Relevance to Crisis Standards of Care

This cohort study compares mortality among Black and White patients with equivalent Sequential Organ Failure Assessment (SOFA) Scores and their odds of death with equivalent priority in Crisis Standards of Care.

This supplemental material has been provided by the authors to give readers additional information about their work. Definition of the Included and Excluded Cohort: (1) Method to identify first ICU stay during hospitalization, and Transferred patients: Eligible patientunitstayid's were identified from the Patients table. Records were excluded if the ICU stay was not the first during a hospitalization. The first ICU stay during a hospitalization was identified using the unitvisitnumber field, and was required to be "1". Patients who were transferred were identified using the hospitaladmitsource and unitadmitsource fields. Patients were excluded if the hospitaladmitsource or unitadmitsource was listed as "Other Hospital", "Other ICU", "ICU", or "ICU to SDU". For the PF ratios compiled from both the respiratoryCharting and treatments tables, progressively less stringent time restrictions were imposed as follows: we initially specified that the PaO2 had to be recorded within 90 minutes of the recorded FiO2 value; when a value was not available within 90 minutes, then a value up to 180 minutes after the FiO2 recording was accepted; when this was unavailable, a value up to 6 hrs was accepted; then a value up to 12hrs later, and finally a value up to 24hrs after the recorded FiO2 was accepted. The lowest PF ratio within 24hrs was retained for final analysis, and there were 45,136 PF ratios associated with eligible ICU stays for analysis.
When data was not available to calculate a PF ratio as described above, an SF ratio was calculated. The SF ratio was based preferentially on the FiO2 recorded in the respiratoryCharting table as described above. When this was not available, then the FiO2 was obtained from the treatments table as described above. We specified that the saturation had to be recorded after the FiO2, and we used the saturation recorded soonest after the highest recorded FiO2 within 24hrs of ICU admission. Saturations recorded more than 6hrs after the highest recorded FiO2 were not eligible for consideration. The SF ratio was then calculated and converted to a respiratory SOFA score according to the scale reported by Grissom et al. in their description of the mSOFA for critical care triage. 4 We performed a sensitivity analysis that was restricted to samples with PF ratios only; SF ratios were excluded from this analysis.
Cardiac SOFA: MAP was preferentially obtained from the meanBp field of the apacheApsVar table. When not available here, it was obtained from the noninvasivemean field of the vitalAperiodic table. The lowest value from within 24 hours of ICU admission was selected. Vasopressors were identified in the infusionDrug table, via identifying generic and trade names of the medications. Vasoactive medications included Dobutamine, Milrinone, Dopamine, Norepinephrine, Epinephrine, Phenylephrine, and Vasopressin. Angiotensin II was not in use at the time of data extraction for this cohort. Many of the vasoactive doses could not be reconciled with standard doses, even after rigorous analysis and cleaning, possibly due to faulty data entry or alternative reporting of dose. Therefore, we performed a sensitivity analysis in which we looked only at the number of vasoactive medications, without taking dose into account. This is similar to methods described by previous investigators. 5 In this analysis, 2 points were assigned for use of Dobutamine, 3 points were assigned for use of 1 vasopressor (Dopamine, Norepinephrine, Epinephrine, Phenylephrine, or Vasopressin), and 4 points were assigned for use of 2 vasopressors.
Liver SOFA: Bilirubins were preferentially obtained from the apacheApsVar table (values are from the first 24hrs of ICU stay).
When not available in the apacheApsVar table, then the highest bilirubin from within 24 hours of ICU admission was obtained from the labs table. When not available in the labs table, then the highest value from the same hospitalization, but prior to 24hrs within ICU admission was accepted.

Kidney SOFA:
Creatinine and urine output were preferentially obtained from the apacheApsVar table. When values were not available there, the creatinine was obtained from the labs table. When not available in the apacheApsVar table, urine output was obtained from the intakeOuput table, by identifying values labeled "urine" or "Nephrostomy". The values from the 24hrs prior to admission were significantly lower than the values from the 24hrs after admission. This was interpreted to likely reflect better recording in the 24hrs after ICU admission. Therefore, Urine output was only accepted from the first 24hrs after ICU admission.
Hematologic SOFA: Platelet counts were obtained from the lab table. The lowest platelet count within 24hrs of ICU admission was selected, and the SOFA score was calculated using this value.

Neurologic SOFA:
Glasgow Coma Scale (GCS) was preferentially obtained from the apacheApsVar To test for the effects of our methods of defining SOFA components, we performed sensitivity analyses with two variations of the SOFA score described in eTable 1.
We tested for an interaction between Race and the SOFA score with hierarchical conditional logistic regression, with fixed effects according to hospital using the clogit command in Stata. The formula for this analysis was: Mortality ~ SOFA+SOFA*Race (grouped by hospital) To evaluate priority scores (system A, system B, and system C), we used the following formula with the clogit 6 command: Formula: Mortality~X + X*Race, group(hospital) X = Priority scores using the thresholds in A, B, or C.
To control for patients who may have been hospitalized multiple times (but who can only die once), we performed one sensitivity analysis with the formula: The formula to evaluate the relationship between SOFA components and mortality was: Mortality~Resp_SOFA+Resp_Race_Interaction + Cardiac_SOFA + Cardiac_Race_Interaction + Kidney_SOFA + Kidney_Race_Interaction + Liver_SOFA + Liver_Race_Interaction + Heme_SOFA + Heme_SOFA_Interaction + Neuro_SOFA + Neuro_SOFA_Interaction, group (hospital) eTable 1. Sequential Organ Failure Assessment Score Variations Used in Primary and Sensitivity Analyses by Race eTable 1 Legend: We tested 3 variations of the SOFA score. The SOFA score tested in the primary analysis is described in the text. We also performed a sensitivity analysis in which the respiratory SOFA was based on PF ratio only, without inclusion of SOFA scores based on the SF ratio. We also tested a variation of the Cardiac SOFA in which the score was based on number of vasoactive medications irrespective of dose. Sensitivity analyses included (1) incorporating a patient-level indicator variable for patients who had multiple hospitalizations, (2) including only 1 randomly selected hospitalization per patient, (3) including only patients who did not receive dialysis during or prior to SOFA calculation, (4) including only patients treated in Medical ICUs, or Medical-Surgical ICUs, (5) including only patients whose primary admission diagnosis was respiratory failure, (6) including only patients treated with "Full Therapy" (no DNR or other limitations), and (7)  .02 Legend: Formula tested was Mortality~Respiratory_SOFA + Respiratory_SOFA*Race + Liver_SOFA + Liver_SOFA*Race + Cardiac_SOFA + Cardiac_SOFA*Race + Kidney_SOFA + Kidney_SOFA*Race + Neurologic_SOFA + Neurologic_SOFA*Race + Hematologic_SOFA+Hematologic_SOFA*Race. This formula was tested within a hierarchical logistic regression framework with a fixed effect term for hospital. Abbreviations: 95% CI, 95% Confidence Interval Legend eFigure 3: Mortality was calculated for Black and White patients associated with each SOFA component score: (a) Respiratory SOFA, (b) Cardiac SOFA, (c) Liver SOFA, (d) Kidney (renal) SOFA, (e) Hematologic SOFA, and (f) Neurologic SOFA. * indicates significance (p<0.05) by chi-square to test for differences in mortality between Black and White patients with the same SOFA component score. Results of the adjusted analysis are presented in the text and this supplement (eTable 4). In the adjusted analysis, only the Kidney (renal) and Hematologic components were significantly associated with race as predictors of mortality.   . Sensitivity analyses were describd in the text, and included (1) a model with a patient-level variable indicating whether a patient had been hospitalized more than once, (2) a model fit by including only one randomly selected hospitalization per patient, (3) excluding any patients who received dialysis during or prior to SOFA calculation, (4) a calculation relying only on number of vasoactive medications irrespective of doses, (5) a SOFA calculation relying only on PF ratios and excluding records that did not have a PF ratio available for calculation, and (6)  Legend: As described in the main text and eTable 2, Systems A & C attempt to save life-years as well as lives by deprioritizing patients with life-limiting moderate or severe comorbidities. We performed a sensitivity analysis in which we added comorbidity points and re-classified patients' priorities based on both SOFA and Comorbidity points as recommended in these guidelines. Thresholds for "moderate" and "severe" comorbidities were CCI of 3 and 8, respectively, as recommended in the Crisis Standard of Care guideline from Colorado. Significant differences in in-hospital mortality persisted between Black and White patients in systems A & C after incorporation of comorbidities. Importantly, improving in-hospital mortality is not the goal of incorporating comorbidities.