Estimation of blood haemoglobin concentration using the HemoCue® during caesarean section: the effect of sampling site

Accuracy of point-of-care testing devices for haemoglobin in the operating room: meta-analysis

BACKGROUND

Point-of-care tests (POCT) for haemoglobin are increasingly used to guide intraoperative transfusion. However, their accuracy compared to central laboratory tests is unknown. The objective was to perform a systematic review and meta-analysis of method comparison studies assessing the accuracy of POCT versus central laboratory haemoglobin tests in patients undergoing surgery.

METHODS

Electronic databases were searched from inception to April 2020 (updated August 2023). Any methodological approach comparing haemoglobin measurements between POCT and central laboratory in patients undergoing surgery under anaesthesia in the operating room were included. Data abstraction was guided by PRISMA and risk of bias was assessed by QUADAS-2. Data were extracted independently and in duplicate by two reviewers. Outcomes included mean differences between POCT and central laboratory haemoglobin with associated standard deviations and 95% limits of agreement (LOA).

RESULTS

Of 3057 citations, 34 studies were included (n = 2427, 6857 paired measurements). Several devices were compared (pulse co-oximetry, n = 25; HemoCue, n = 10; iSTAT, n = 6; blood gas analysers, n = 10; haematology analyser, n = 2). Median sample size was 41 patients, and 11 studies were funded by device manufacturers. Fifteen of 34 studies had low risk of bias. Pooled mean differences (95% LOA) were: pulse co-oximeters 2.3 g/l (-25.2-29.8), HemoCue -0.3 g/l (-11.1-10.5), iSTAT -0.3 g/l (-8.4-7.8) and blood gas analysers -2.6 g/l (-17.8-12.7).

CONCLUSION

All POCT examining intraoperative haemoglobin measurement yielded pooled mean difference LOAs larger than the allowable limit difference of ±4 g/dl. Intraoperative haemoglobin measured by POCT should not be considered interchangeable with central laboratory values and caution is necessary when using these tests to guide intraoperative transfusion.

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.

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

The laboratory analysis provides accurate, but time consuming hemoglobin level estimation especially in the emergency setting. The reliability of time-sparing point of care devices (POCT) remains uncertain. We tested two POCT devices accuracy (HemoCue^®201⁺ and Gem^®Premier™3000) in routine emergency department workflow. Blood samples taken from patients admitted to the emergency department were analyzed for hemoglobin concentration using a laboratory reference Beckman Coulter LH 750 (HB_LAB), the HemoCue (HB_HC) and the Gem Premier 3000 (HB_GEM). Pairwise comparison for each device and Hb_LAB was performed using correlation and the Bland-Altman methods. The reliability of transfusion decision was assessed using three-zone error grid. A total of 292 measurements were performed in 99 patients. Mean hemoglobin level were 115 ± 33, 110 ± 28 and 111 ± 30 g/l for Hb_HC, Hb_GEM and Hb_LAB respectively. A significant correlation was observed for both devices: Hb_HC versus Hb_LAB (r² = 0.93, p < 0.001) and HB_GEM versus HB_LAB (r² = 0.86, p < 0.001). The Bland-Altman method revealed bias of -3.7 g/l (limits of agreement -20.9 to 13.5) for HB_HC and HB_LAB and 2.5 g/l (-18.6 to 23.5) for HB_GEM and HB_LAB, which significantly differed between POCT devices (p < 0.001). Using the error grid methodology: 94 or 91 % of values (Hb_HC and Hb_GEM) fell in the zone of acceptable difference (A), whereas 0 and 1 % (Hb_HC and Hb_GEM) were unacceptable (zone C). The absolute accuracy of tested POCT devices was low though reaching a high level of correlation with laboratory measurement. The results of the Morey´s error grid were unfavorable for both POCT devices.

[Evaluation of the measurement of hemoglobin by the Hemocue System® in the preterm neonate less than 28 days old]

BACKGROUND

Hemoglobin (Hb) measurement is essential for the monitoring of anemia in preterm neonates to assess if any bleeding (pulmonary, cerebral, digestive) is present. EDTA samples require 500 μL vs. 10 μL for the Hemocue(®) system. This system has been evaluated and validated in adults and children but not in preterm neonates with fetal hemoglobin. The aim of the study was to compare Hb measurement with the Hemocue(®) system vs. the EDTA laboratory system on fetal Hb in preterm neonates.

MATERIALS AND METHODS

This was a prospective study conducted in the preterm intensive care unit in the Amiens Hospital. Preterm neonates, before 28 days of life, requiring EDTA (Hb) measurement were included. Two Hemocues(®) were performed at the same time. Postnatal age (correlated to the fetal hemoglobin level decrease), blood sample site, and other factors that could influence the Hb result were evaluated.

RESULTS

Seventy-six EDTA and 152 Hemocue(®) samples from 38 preterm neonates were included. The term was 28.1±3.7 weeks of gestation, the birth weight was 1215.5±657 g. We found a good correlation between the Hemocue(®) and EDTA samples (Hemocue(®)=EDTA*0.94-0.4; R(2)=0.63; P<0.001). The influence of confounding factors was insignificant.

CONCLUSION

The use of the Hemocue(®) system showed a good correlation with the EDTA measurement of fetal Hb, with a moderate bias (-0.2±1.5 g/dL), which remained stable for the first 28 days of life.

Systematic Review and Meta-Analysis of Method Comparison Studies of Masimo Pulse Co-Oximeters (Radical-7™ or Pronto-7™) and HemoCue® Absorption Spectrometers (B-Hemoglobin or 201+) with Laboratory Haemoglobin Estimation

We assessed agreement in haemoglobin measurement between Masimo pulse co-oximeters (Rad-7™ and Pronto-7™) and HemoCue® photometers (201+ or B-Hemoglobin) with laboratory-based determination and identified 39 relevant studies (2915 patients in Masimo group and 3084 patients in HemoCue group). In the Masimo group, the overall mean difference was -0.03 g/dl (95% prediction interval -0.30 to 0.23) and 95% limits of agreement -3.0 to 2.9 g/dl compared to 0.08 g/dl (95% prediction interval -0.04 to 0.20) and 95% limits of agreement -1.3 to 1.4 g/dl in the HemoCue group. Only B-Hemoglobin exhibited bias (0.53, 95% prediction interval 0.27 to 0.78). The overall standard deviation of difference was larger (1.42 g/dl versus 0.64 g/dl) for Masimo pulse co-oximeters compared to HemoCue photometers. Masimo devices and HemoCue 201+ both provide an unbiased, pooled estimate of laboratory haemoglobin. However, Masimo devices have lower precision and wider 95% limits of agreement than HemoCue devices. Clinicians should carefully consider these limits of agreement before basing transfusion or other clinical decisions on these point-of-care measurements alone.

Hemoglobin point-of-care testing: the HemoCue system

Besides the use of traditional laboratory resources, the diagnosis of anemia can also be accomplished by assessing hemoglobin (Hb) concentration with point-of-care testing (POCT) devices such as the HemoCue test systems. In several situations, these devices might suitably replace traditional laboratory testing, including several areas of health care where a very rapid Hb measurement might be required to make immediate therapeutic decisions. The use of these devices, however, should fulfill some basic criteria, including economic, clinical, and regulatory issues; appropriate training of the users and knowledge of test requirements, performance, limitations, and potential interferences; the use of venous and arterial sampling, when possible; and a rigorous quality assessment, which should be under the responsibility of laboratory professionals. Because of its optimal performance along with the fact that the HemoCue is probably one of the most commonly used devices worldwide, the aim of this article is to review the literature data about the performance of this test system as compared with laboratory reference testing estimations and according to the biological matrix.

Electro-optical plethysmography for non-invasive estimation of hemoglobin concentration

Novel sensors and instrumentation are currently being investigated with the intended application of determining the concentration of hemoglobin and other optically absorbing compounds in blood using non-invasive methods. In order to measure concentration, the mass or amount of a compound must be known in addition to the volume of liquid. In principle, it may be possible to estimate hemoglobin concentration from a change in optical absorbance occurring over the cardiac cycle divided by a corresponding change in measured blood volume during the cycle measured from peripheral tissue, e.g. the finger or ear. Electrical and optical sensors were evaluated in vitro using a tissue phantom and an absorbing liquid medium. The effect of changes in optical absorption and pulse pressure on the capacitance and optical absorbance were studied.

Evaluation of electrical and optical plethysmography sensors for noninvasive monitoring of hemoglobin concentration

Completely noninvasive monitoring of hemoglobin concentration has not yet been fully realized in the clinical setting. This study investigates the viability of measuring hemoglobin concentration noninvasively by evaluating the performance of two types of sensor using a tissue phantom perfused with a blood substitute. An electrical sensor designed to measure blood volume changes during the cardiac cycle was used together with an infrared optical sensor for detection of erythrocyte-bound hemoglobin. Both sensors demonstrated sensitivity to changes in pulse volume (plethysmography). The electrical sensor produced a signal referred to as capacitance plethysmograph (CPG) a quantity which was invariant to the concentration of an infrared absorbing dye present in the blood substitute. The optical sensor signal (photoplethysmograph) increased in amplitude with increasing absorber concentration. The ratio PPG:CPG is invariant to pulse pressure. This quantity is discussed as a possible index of in vivo hemoglobin concentration.