Comparison of the accuracy of hemoglobin point of care testing using HemoCue and GEM Premier 3000 with automated hematology analyzer in emergency room

Current Status of Measurement Accuracy for Total Hemoglobin Concentration in the Clinical Context

OBJECTIVE

The main objective of this investigation is to provide data about the accuracy of total hemoglobin concentration measurements with respect to clinical settings, and to devices within the categories of point-of-care and reference systems. In particular, tolerance of hemoglobin concentrations below 9 g/dL that have become common in clinical practice today determines the need to demonstrate the limits of measurement accuracy in patient care.

METHODS

Samples extracted from six units of heparinized human blood with total hemoglobin concentrations ranging from 3 to 18 g/dL were assigned to the test devices in a random order. The pool of test devices comprised blood gas analyzers, an automatic hematology analyzer, a laboratory reference method, and the point-of-care system HemoCue. To reduce the pre-analytic error, each sample was measured three times. Due to the characteristics of the tested devices and methods, we selected the mean values of the data from all these devices, measured at the corresponding total hemoglobin concentrations, as the reference.

MAIN RESULTS

The measurement results of the test devices overlap within strict limits (R2 = 0.999). Only the detailed analysis provides information about minor but systematic deviations. In the group of clinically relevant devices, which are involved in patient blood management decisions, the relative differences were within the limit of +/- 5 % for values down to 3 g/dL.

CONCLUSIONS

A clinically relevant change of +/- 0.5 g/dL of total hemoglobin concentration can be detected with all selected devices and methods. Compliance with more stringent definitions-these are the relative differences of 5 % in relation to the corresponding reference values and the clinically adapted thresholds in the format of a tolerance level analysis-was achieved by the clinical devices assessed here.

Multicenter comparison of three intraoperative hemoglobin trend monitoring methods

Transfusion decisions are guided by clinical factors and measured hemoglobin (Hb). Time required for blood sampling and analysis may cause Hb measurement to lag clinical conditions, thus continuous intraoperative Hb trend monitoring may provide useful information. This multicenter study was designed to compare three methods of determining intraoperative Hb changes (trend accuracy) to laboratory determined Hb changes. Adult surgical patients with planned arterial catheterization were studied. With each blood gas analysis performed, pulse cooximetry hemoglobin (SpHb) was recorded, and arterial blood Hb was measured by hematology (tHb), arterial blood gas cooximetry (ABGHb), and point of care (aHQHb) analyzers. Hb change was calculated and trend accuracy assessed by modified Bland–Altman analysis. Secondary measures included Hb measurement change direction agreement. Trend accuracy mean bias (95% limits of agreement; g/dl) for SpHb was 0.10 (− 1.14 to 1.35); for ABGHb was − 0.02 (− 1.06 to 1.02); and for aHQHb was 0.003 (− 0.95 to 0.95). Changes more than ± 0.5 g/dl agreed with tHb changes more than ± 0.25 g/dl in 94.2% (88.9–97.0%) SpHb changes, 98.9% (96.1–99.7%) ABGHb changes and 99.0% (96.4–99.7%) aHQHb changes. Sequential changes in SpHb, ABGHb and aHQHb exceeding ± 0.5 g/dl have similar agreement to the direction but not necessarily the magnitude of sequential tHb change. While Hb blood tests should continue to be used to inform transfusion decisions, intraoperative continuous noninvasive SpHb decreases more than − 0.5 g/dl could be a good indicator of the need to measure tHb.

Methods and analyzers for hemoglobin measurement in clinical laboratories and field settings

This paper describes and compares methods and analyzers used to measure hemoglobin (Hb) in clinical laboratories and field settings. We conducted a literature review for methods used to measure Hb in clinical laboratories and field settings. We described methods to measure Hb and factors influencing results. Automated hematology analyzer (AHA) was reference for all Hb comparisons using evaluation criteria of ±7% set by College of American Pathologists (CAP) and Clinical Laboratory Improvement Amendments (CLIA). Capillary fingerprick blood usually produces higher Hb concentrations compared with venous blood. Individual drops produced lower concentrations than pooled capillary blood. Compared with the AHA: (1) overall cyanmethemoglobin (1.0-8.0  g/L), WHO Colour Scale (0.5-10.0  g/L), paper-based devices (5.0-7.0  g/L), HemoCue® Hb-201 (1.0-16.0  g/L) and Hb-301 (0.5-6.0  g/L), and Masimo Pronto® (0.3-14.0  g/L) overestimated concentrations; (2) Masimo Radical®-7 both under- and overestimated concentrations (0.3-104.0  g/L); and (3) other methods underestimated concentrations (2.0-16.0  g/L). Most mean concentration comparisons varied less than ±7% of the reference. Hb measurements are influenced by several analytical factors. With few exceptions, mean concentration bias was within ±7%, suggesting acceptable performance. Appropriate, high-quality methods in all settings are necessary to ensure the accuracy of Hb measurements.This paper describes and compares methods and analyzers used to measure hemoglobin (Hb) in clinical laboratories and field settings. With few exceptions, mean concentration bias was within ±7%, suggesting acceptable performance. Appropriate, high-quality methods in all settings are necessary to ensure the accuracy of Hb measurements.

Accuracy of pulse oximeters at low oxygen saturations in children with congenital cyanotic heart disease: An observational study

BACKGROUND

Pulse oximetry overestimates arterial oxygen saturation (SaO₂ ) at less than 90% saturation in cyanotic children. The Masimo Blue sensor (Masimo Corp., Irvine, CA) is a pulse oximetry sensor developed for use in children with cyanosis. However, there remains a lack of research in actual clinical practice.

AIMS

We evaluated the intraoperative performance of three different pulse oximeters to measure oxyhemoglobin saturation (SpO₂ ) at low saturations in pediatric patients with cyanotic heart disease and the influence of clinical variables (SaO₂ , hemoglobin concentration, perfusion index, and weight) on the accuracy of the sensors.

METHODS

This prospective observational study compared SpO₂ measured using three pulse oximeters (Masimo Blue [Masimo Corp., Irvine, CA]; Masimo LNCS, and Nellcor [Medtronic, Dublin, Ireland]) at selected SaO₂ ranges (≥85%, 75%-84%, 60%-74%, and < 60%). Accuracy was evaluated according to bias and Bland-Altman analysis with appropriate correction for multiple measurements. Relationships between bias and clinical variables were assessed using a generalized estimating equation.

RESULTS

Two hundred and fifty-eight samples were analyzed. The mean overall bias (limits of agreement) of Masimo Blue, Masimo LNCS, and Nellcor sensor was -5.3 (-20.9 to 10.3%), -7.4 (-21.9 to 7.1%), and -7.4 (-22.5 to 15.1%), respectively. However, there was no difference in bias among the three sensors at SaO₂ <60%. Generalized estimating equation showed that SaO₂ value was associated with bias of all sensors. Perfusion index affected the bias of Blue sensor and LNCS sensor, and patients' weight was associated with bias of Nellcor sensor.

CONCLUSION

Masimo blue sensor demonstrated overall lower bias compared to the other two sensors. However, the accuracy of all sensors was similarly poor at SaO₂ less than 60%. Bias was influenced by SaO₂ , perfusion index, and body weight.

Reliability of Point-of-Care Hematocrit Measurement During Liver Transplantation

BACKGROUND

Although point-of-care (POC) analyzers are commonly used during liver transplantation (LT), the accuracy of hematocrit measurement using a POC analyzer has not been evaluated. In this retrospective observational study, we aimed to evaluate the accuracy of hematocrit measurement using a POC analyzer and identify potential contributors to the measurement error and their influence on mistransfusion during LT.

METHODS

We retrospectively collected 6461 pairs of simultaneous intraoperative hematocrit measurements using POC analyzers and laboratory devices during LTs in 901 patients. The agreement of hematocrit measurements was assessed using Bland-Altman analysis for repeated measurements, while the incidence and magnitude of hematocrit measurement error were compared among 16 different laboratory abnormality categories. A generalized estimating equation analysis was performed to identify potential contributors to falsely low-measured POC hematocrit. Additionally, we defined potential "overtransfusion" in the case when POC hematocrit was <20% and laboratory hematocrit was ≥20% and investigated its association with intraoperative transfusion.

RESULTS

The POC hematocrit measurements were falsely lower than the laboratory hematocrit measurements in 70.3% (4541/6461) of pairs. The median (interquartile range) of hematocrit measurement error was -1.20 (-2.60 to 0.20). Bland-Altman analysis showed that 24.5% (1583/6461) of the errors were outside our a priori defined clinically acceptable limits of ±3%. The incidence of falsely low-measured hematocrit was significantly higher with the presence of concomitant hypoalbuminemia and hypoproteinemia. Hypoalbuminemia combined with hyperglycemia showed significantly larger hematocrit measurement error. Hypoalbuminemia, hypoproteinemia, and hyperglycemia were predictors of falsely low-measured hematocrit. Furthermore, the overtransfusion group showed larger amount of transfusion than the adequately transfused group, with a median difference of 2 units (95% confidence interval [0-4], P = .039), despite similar amount of blood loss.

CONCLUSIONS

Hematocrit measured using the POC device tends to be lower than the laboratory hematocrit measured during LT. Commonly encountered laboratory abnormalities during LT include hypoalbuminemia, hypoproteinemia, and hyperglycemia, which may contribute to falsely low-measured POC hematocrit. Careful consideration of these confounders may help reduce overtransfusion that occurs due to falsely low-measured POC hematocrit.