Differences in Arterial Blood Gas Testing by Race and Sex across 161 U.S. Hospitals in Four Electronic Health Record Databases

Rationale: Pulse oximetry accuracy varies across races, underscoring the importance of routine arterial blood gas (ABG) testing, the gold standard for assessing oxygen saturation. Objectives: This study aimed to assess disparities in ABG testing among critically ill patients by race and sex. Methods: Records from 2001 to 2019 in 161 U.S. hospitals were analyzed, including Duke, MIMIC-III (Medical Information Mart for Intensive Care), MIMIC-IV, and the eICU Collaborative Research Database. The study evaluated ABG test incidence; time to first test; and frequency of subsequent tests, adjusting for confounders, including the Sequential Organ Failure Assessment, hospital, and age. Subgroup analyses focused on patients with arterial lines and mechanical ventilation. Measurements and Main Results: The cohort included 184,178 ICU admissions (35.0% with ABG test results; 1.9% Asian, 16.5% Black, 3.5% Hispanic or Latino, 78.1% White, 45.7% female). Compared with White patients, Asian, Black, and Hispanic or Latino patients were less likely to have an ABG test (odds ratio [OR] [95% confidence interval (CI)], 0.807 [0.741, 0.879]; 0.859 [0.830, 0.888]; 0.919 [0.865, 0.976], respectively), experienced delays to initial ABG testing (hazard ratio [HR] [95% CI], Asian, 0.855 [0.803, 0.911]; Black, 0.833 [0.814, 0.853]; P < 0.001), and were less likely to have repeated ABG tests (incidence rate ratio [95% CI], Asian 0.913 [0.845, 0.986]; Black 0.913 [0.887, 0.940]). Compared with male patients, female patients underwent fewer ABG tests (OR [95% CI], 0.926 [0.905, 0.948]), had delays in initial testing (HR [95% CI], 0.958 [0.942, 0.974]), and had fewer repeated ABG tests (incidence rate ratio [95% CI], 0.951 (0.931, 0.971)). These findings were consistent among patients who were mechanically ventilated and had arterial lines placed. Conclusions: Asian, Black, and female patients had significantly reduced and delayed rates of ABG testing. Inequitable ABG testing may exacerbate the prevalence of hidden hypoxemia. Until skin tone-corrected pulse oximeters are available, equitable ABG testing remains the best strategy to mitigate hidden hypoxemia.