Accuracy of the HemoCue® to measure cell-free plasma hemoglobin and detect clinically significant hemolysis

Abstract

Introduction

Monitoring cell-free plasma hemoglobin (PHb) during extracorporeal therapies allows early intervention of significant hemolysis, but timely measurements are often challenging. We thus present an analysis of a rapid benchtop device’s ability to detect clinically significant hemolysis (PHb ≥50 mg/dL).

Methods

PHb was measured in 419 plasma samples from 88 pediatric patients undergoing cardiopulmonary bypass via both the benchtop device (HemoCue® Plasma/Low Hb system) and the clinical laboratory at the Children’s Hospital of Pittsburgh (reference standards). Values of PHb ≥50 mg/dL as measured by the reference standard was defined as the binary outcome of clinically significant hemolysis. Analyses included Pearson correlations, logistic regression, receiver operating characteristic curves, and Bland-Altman. Because the manufacturer specifications identify the measurement range of the HemoCue® system as 30-3000 mg/dL, a secondary analysis was completed using PHb ≥30 mg/dL.

Results

Using reference measurements, 66/88 subjects had at least one PHb level that fell within the range of detection (≥30 mg/dL) of the benchtop device and 46/88 had significant hemolysis as defined by PHb ≥50 mg/dL. PHb levels ≥30 mg/dL largely correlated with measurements made with the benchtop device (r = 0.82, p < .001). The device was able to predict PHb values ≥30 mg/dL (AUROC 0.9582) and ≥50 mg/dL (AUROC 0.9637). The Bland-Altman demonstrated a mean difference of 7.0 mg/dL with <5% outside the 95% limits of agreement.

Conclusions

The HemoCue® system is an effective surrogate for more robust laboratory testing to identify clinically significant hemolysis during cardiopulmonary bypass.