Accuracy of bedside point of care testing in critical emergency department patients

Point-of-care (POC) testing reduces laboratory turn-around having the potential to improve timely diagnosis and management. We compared the accuracy of nurse performed POC and core laboratory testing and determined whether deviations between the two were clinically meaningful.

We performed a prospective, observational study on a convenience sample of 50 critical care ED patients in whom a POC chemistry and hematocrit was ordered. Blood samples were divided into 2 aliquots; one sample was tested by the treating nurse using a handheld POC device and the other sample was tested in the core laboratory. Paired comparisons of test results were performed using Pearson's correlation coefficients, Lin concordance coefficients, and Bland Altman plots.

Mean patient age was 67, 50% were male, 82% were admitted. Pearson's correlation and Lin concordance coefficients were excellent (0.84-1.00) for all 8 analytes. Mean (95%CI) paired differences between POC and core laboratory measurements were Na⁺ 0.30 (-0.22 to 0.82) mmol/L, K⁺-0.12 (-0.14 to - 0.09) mmol/L, Cl^- 2.10 (1.41 to 2.78) mmol/L, TCO₂-1.68 (-2.06 to -1.30) mmol/L, glucose 2.46 (1.46 to 3.46) mg/dL, BUN, 1.69 (0.95 to 2.42) mg/dL, creatinine 0.13 (0.08 to 0.17) mg/dL, and hematocrit -0.39 (-0.93 to 0.15) %. In 3 of 400 measurements, the difference between POC and core lab exceeded the maximal clinically acceptable deviation based on physician surveys.

Bedside POC by ED nurses is reliable and accurate and does not deviate significantly from core laboratory testing by trained technicians.