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

<b>Rationale:</b> Pulse oximetry accuracy varies across races, underscoring the importance of routine arterial blood gas (ABG) testing, the gold standard for assessing oxygen saturation. <b>Objectives:</b> This study aimed to assess disparities in ABG testing among critically ill patients by race and sex. <b>Methods:</b> 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. <b>Measurements and Main Results:</b> 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]; <i>P</i> < 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. <b>Conclusions:</b> 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.