An Evaluation of the HemoCue Assay for the Rapid Assessment of Plasma Free Hemoglobin in Pediatric Patients Undergoing Extracorporeal Membrane Oxygenation (ECMO)
Creators: name: Gowani, F.
Publisher: name: Zenodo
Year: 2015
Subjects: HemoCue Assay
Plasma Free Hemoglobin

description: <strong>Background</strong>: Extracorporeal membrane oxygenation (ECMO) therapy on newborns is associated with increased risk of hemolysis which can lead to hemoglobin associated nephropathy and, in some cases, acute renal failure. Accordingly, ECMO patient care guidelines stress the importance of early detection of ECMO associated hemolysis <em>via </em>measurement of the levels of plasma free hemoglobin.

<strong>Objective</strong>: To verify the accuracy and precision of the HemoCue spectrophotometric method for assessment of plasma free hemoglobin (PfHb) on ECMO patients with a focus on values in the lower range of detection.

<strong>Methods</strong>: HemoCue (HemoCue, Brea, CA ) PfHb results were compared to those obtained on the well-established Abbott Architect (AA) c4000 analyzer (Abbott Laboratories, Chicago, IL). The HemoCue method 1) oxidizes hemoglobin to methemoglobin with nitrite, then 2) after conversion to azidemethemoglobin, absorbance is measured at 570 and 880 nm. Potential interferences were assessed by performing a spectrophotometric scan on our Cary 100 (Agilent, Santa Clara, CA) in order to determine the degree of spectral overlap with bilirubin and lipoprotein, the latter being partially corrected using the 880 nm absorbance reading. In addition, analysis for bilirubin and triglyceride was performed. Also, as an adjunct marker for hemolysis, lactate dehydrogenase was measured. Precision studies were based on replicate analysis on patient plasma samples. Assays were also performed on ultracentrifuged samples with results compared to those obtained on neat and filtered samples. Serial dilution recovery studies were performed on a lysed sample with a known/measured hemoglobin value (Unicel DxH800, Beckman Coulter, Brea, CA).

<strong>Results</strong>: Linear regression analysis showed a significant proportional error with results 29 percent lower on the Hemocue method (Hemocue=0.71*AA + 4.8; R2 = 0.70, N = 22). Two samples with triglyceride &gt; 400 mg/dL showed spuriously high Hemocue values. No statistical difference in mean values was observed between the two methods (t Stat = 0.165, P = 0.870). Serial dilution recovery on the Hemocue method was 106 percent (Hemocue (7.2 g/dL) versus DxH800 (6.8 g/dL)). The serial dilution curve plot showed an excellent fit with an expected log relationship (Hemocue = -111.5*ln(Dilution Factor) + 594.3). Precision studies showed CV% at seven levels ranging from 9.7- 4.2 percent. LDH showed positive correlation with PfHb values obtained on the AA method (AA = 5.9*LDH + 290; R2=0.44). As expected, bilirubin levels showed a positive PfHb interference, the latter increasing slightly with the bilirubin level. Neat samples tested versus filtered samples showed no significant difference whereas ultracentrifuged samples consistently gave lower PfHb values.

<strong>Conclusions</strong>: The HemoCue method provides rapid and reasonably accurate measurements of plasma free hemoglobin. However, our study suggests that levels in the 10 to 30 mg/dL range should be interpreted with caution. Triglyceride and bilirubin both interfere in a proportional manner and must be considered when interpreting results on unfiltered samples. Adding LDH as a surrogate hemolysis marker appears to be of marginal value.
description: https://www.2019aacc.org/abstracts/annual-meeting-abstract-archive/2015-annual-meeting-archive