Retrospective Analysis of Point-of-Care Venous Blood Gas and Central Lab Testing in the Emergency Department

Point-of-care (POC) testing in the emergency department (ED) can allow for rapid diagnosis and treatment. Prior studies have shown good agreement between POC venous blood gas (VBG) testing and central lab measurements. Clinical experience in the ED at our institution has led to continued skepticism about the reliability of certain values obtained by POC testing. Here, we evaluate the agreement between POC VBG’s in the ED and central lab testing.

This was a retrospective evaluation of POC lab values compared to central lab results in the adult ED of an urban, academic medical center in the United States from 12/29/2017 - 10/21/2025. POC VBG tests were run on an epoc Blood Analysis System (Siemens), which undergoes routine quality assurance (QA) procedures. All POC VBG tests with a collection time within 12 minutes of that of a central lab test were queried from the hospital’s clinical information system. The pH, pCO2, bicarbonate (Bicarb), sodium (Na+), potassium (K+), chloride (Cl-), Creatinine (Cr), hematocrit (Hct), and lactic acid (LA) were analyzed. Pearson’s correlation coefficient (r) was calculated for each set of values. Agreement was assessed using Bland-Altman plots to calculate a 95% confidence interval.

Of the POC values analyzed, Cr had the highest agreement and correlation coefficient with central lab testing (92.6%, r = 0.983, n = 26,409), with LA showing similarly high agreement and correlation (88.4%, r = 0.951, n = 10,216). Hct had among the lowest levels of agreement (63.7%, r = 0.730, n = 27,078). Among acid-base values, pH (79.1% r = 0.902, n = 1,735) and pCO2 (78.4%, r = 0.911, n = 873) had the highest, with Bicarb having only 50.2% agreement with formal lab testing (r = 0.880, n = 22,905). Among electrolytes, Na+ demonstrated the highest agreement (83.8%, r = 0.865, n = 26,314), followed by K+ (79.2%, r = 0.739, n = 22,751) and Cl- (65.1%, r = 0.816, n = 26,252).

At our institution, some tests on the POC VBG (Cr, LA, Na+) showed excellent agreement with central lab analysis. Others (K+, Cl-, Bicarb, Hct) had lower agreement than previously reported. This demonstrates that reliance on internal QA and agreements reported by other institutions may be insufficient. For ED’s using POC testing, it’s important to have the data infrastructure to allow for retrospective comparison of POC and formal lab testing.