Point-of-care versus central laboratory measurements of electrolytes and hemoglobin: A prospective observational study in critically ill patients in a tertiary care hospital.

Background: A blood gas analyzer is a point-of-care (POC) testing device used in the Emergency Department (ED) to manage critically ill patients. However, there were differences in results found from blood gas analyzers for hemoglobin (Hgb) and electrolytes parameters. We conducted a comparative validity study in ED in patients who had requirements of venous gas analysis, complete blood count, and electrolytes. The objective was to find the correlation of Hgb, sodium (Na⁺), and potassium (K⁺) values between the blood gas analyzer and laboratory autoanalyzer.

Methods: A total of 206 paired samples were tested for Hgb, Na⁺, and K⁺. Total 4.6 ml of venous blood was collected from each participant, 0.6 ml was used for blood gas analysis as POC testing and 4 ml was sent to the central laboratory for electrolyte and Hgb estimation.

Results: The mean difference between POC and laboratory method was 0.608 ± 1.41 (95% confidence interval [CI], 0.41-0.80; P < 0.001) for Hgb, 0.92 ± 3.5 (95% CI, 0.44-1.40) for Na⁺, and 0.238 ± 0.62 (95% CI, -0.32-0.15; P < 0.001) for K⁺. POC testing and laboratory method showed a strong positive correlation with Pearson correlation coefficient (r) of 0.873, 0.928, and 0.793 for Hgb, Na⁺, and K⁺, respectively (P < 0.001).

Conclusion: Although there was a statistical difference found between the two methods, it was under the United States Clinical Laboratory Improvement Amendment range. Hence, starting the therapy according to the blood gas analyzer results may be beneficial to the patient and improve the outcome.