Comparison between blood hemoglobin concentration determined by point-of-care device and complete blood count in adult patients with dengue.

BACKGROUND: Hematocrit measurement has been an indispensable tool for monitoring plasma leakage and bleeding in dengue patients. However, hematocrit measurement by automated methods is hampered by frequent venipunctures. Utility of point-of-care hemoglobin (POC-Hb) test for monitoring dengue patients has not been established. We evaluated the relationship between hemoglobin measured by POC-Hb testing and hematocrit measured by the automated method in adult dengue patients. METHODOLOGY AND PRINCIPAL FINDINGS: Adult dengue patients were recruited at two university hospitals in Thailand from October 2019 to December 2020. POC-Hb test was performed using capillary blood simultaneously with venipuncture to obtain whole blood for an automated complete blood count (CBC) analysis. The correlation of hemoglobin and hematocrit measurement was evaluated. A total of 44 dengue patients were enrolled. Twenty-nine patients (65.9%) were female, with a median age of 31 years (interquartile range 22-41). Of the enrolled patients, 30 (68.2%), 11 (25.0%), and 3 (6.8%) were classified as dengue without warning signs, with warning signs, and severe dengue, respectively. Seven patients (15.9%) had hemoconcentration, and five patients (11.3%) had bleeding. A total of 216 pairs of POC-Hb and CBC were evaluated. A significant positive correlation was observed between hemoglobin measured by POC-Hb testing and hematocrit measured by an automated CBC (r = 0.869, p <0.001). Bland-Altman analysis between hemoglobin measured by POC-Hb testing and an automated CBC showed a bias of -0.43 (95% limit of agreement of -1.81 and 0.95). Using the cutoff of POC-Hb ≥20% as a criteria for hemoconcentration, the sensitivity and specificity of hemoconcentration detected by POC-Hb device were 71.4% and 100.0%, respectively. CONCLUSIONS: Hemoglobin measurement by POC-Hb testing has a strong correlation with hematocrit in adult patients with dengue fever. However, the sensitivity in detecting hemoconcentration is fair. The adjunct use of capillary POC-Hb testing can decrease the frequency of venipuncture. Further study in children is encouraged.

Accuracy study of a novel alternate method measuring erythrocyte sedimentation rate for prototype hematology analyzer Celltac α.

INTRODUCTION: The erythrocyte sedimentation rate (ESR) is a nonspecific inflammation indicator. In laboratory testing, automated ESR analyzers may use the reference Westergren method (Reference WG), modified Westergren (Modified WG), or Alternate ESR method (Alternate ESR) based on photometric rheology. A prototype hematology analyzer Celltac α+ (Nihon Kohden Corporation) with built-in Novel ESR analysis technology (Novel ESR) was developed to improve the accuracy of Alternate ESR. Alternate ESR uses only the aggregation phase information of Reference WG. The Novel ESR adds sedimentation and packing phase information obtained by hematology analyzer measurands. High correlation with WG was ensured by predicting the ESR value using Hematocrit (Hct) and MCV values as correcting parameters. METHODS: Novel ESR was compared with Modified WG (MONITOR-40, Joko Corporation) and Reference WG, according to internationally recognized guidelines: Precision, carryover, limit of quantification, comparability, linearity, accuracy, and fibrinogen sensitivity. Samples from healthy volunteers and clinical patients were used. The correction performance of Novel ESR and Modified WG was compared with Reference WG by regression analysis in three range categories for ESR and measurands affecting ESR correction (Hct, MCV, and MCH). RESULTS: Novel ESR showed sufficient basic performance and comparability with Modified WG. In the accuracy study comparing with Reference WG, the regression equation was y = 1.026x + 0.5(r =  .945,P <  .001;n = 271). When evaluating the correction performance, the slopes were within 0.8-1.2, except for the high part of Hct. All intercepts were within 10 mm. CONCLUSION: This study validated the correction performance to the initial estimated ESR value by aggregation phase information using information reflecting sedimentation and packing phase obtained from automated hematology analyzer. The Celltac α+ Novel ESR provided results equivalent to Reference WG.

Dried blood spots for anti-doping: Why just going volumetric may not be sufficient.

The perspective discusses quantitative DBS analysis for anti-doping testing in an athletic population and why only using volumetric sampling for this subgroup might not be enough. It presents examples to highlight where HCT variations occur, followed by a whole blood to plasma ratio and an HCT extraction bias discussion. Finally, options to correct for the HCT bias are presented.

On-chip estimation of hematocrit level for diagnosing anemic conditions by Impedimetric techniques.

An on-chip device has been fabricated on Si platform for precise estimation of the hematocrit (Hct) level of human blood with rapid turn out. Impedance/capacitance spectroscopy and current-voltage (I-V) measurements have been employed to observe the variation of electrical parameters of erythrocyte suspensions with varying Hct level. Experimentally obtained values of capacitance, impedance and conductance with Hct level suggests a linear variation. Current-time measurement has also been performed to ensure the susceptibility of red blood cells under a fixed external electric field for certain duration of time. The online real time sample analyzes have also been performed by the device connected with an embedded electronic circuit interfaced with a laptop through appropriate software. This has enabled the development of a novel Si-chip based compact point-of-care (POC) diagnosis system for Hct level estimation by measuring the dielectric/capacitive variation of an erythrocyte cell suspension. The relevant performance parameters of such a compact system including range, resolution, limit of detection and throughput have also been evaluated.

Influence of the static magnetic field on red blood cells parameters and platelets using tests of CBC and microscopy images.

The present study was undertaken to investigate the influence of the static magnetic field (SMF) on the platelets and red blood cells counts (RBCs), haemoglobin (HGB), haematocrit (HCT), mean cell volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) in female rats (in-vitro). The results were analysed using tests of complete blood count (CBC) and microscopic images. The SMF in millitesla (mT) was generated using a fabricated electromagnetic exposure technique, and it has used for different time (minutes) of exposure. Statistical analysis for both tests investigated that the values of SMF affected the RBCs parameters and platelets for exposed Rats significantly for both tests. At 42.5 mT: RBCs counts have been affected (decreased) significantly (p < 0.05) at 30 min exposure, HCT (%) has affected (increased) significantly (p < 0.05) at 10 min and 30 min of exposure. The highest effects of SMF on the values of RBCs, HGB and HCT (%) were found at 34.8 mT after exposed to 15 min Variation of time of exposure and the values of SMF affected (p < 0.05) on the values of RBCs, HGB and HCT (%). The lowest effect of SMF was on the value of MCV (fl) at 6.4 mT at 15 min We found the effects of SMF on the platelet counts significant. Microscopy images of RBCs parameters and platelet count (PLT) support results got from the CBC test.

Analytical validation of the iSED automated analyzer for erythrocyte sedimentation rate.

INTRODUCTION: iSED is an alternate automated analyzer for erythrocyte sedimentation rate (ESR) based on photometric rheology technology that estimates ESR by measuring rouleaux formation. The aim was to evaluate the analytical performance of the iSED analyzer and compare the results with the Westergren method and another alternate ESR analyzer, TEST1. METHODS: Validation was performed at two study sites according to the recommendations by the International Council for Standardization in Haematology and included determination of intrarun precision and inter-run precision, bias, carryover, and method comparison, which was further assessed for samples with normal and low hematocrit, as well as per low, middle, and upper third of the analytical range. RESULTS: Intrarun coefficients of variation (CVs) with commercial controls were 4.0% and 1.8%, while inter-run CVs 7.5% and 0.7%, for the normal and pathological range, respectively. Intrarun CVs obtained with patient samples were 19.9%, 9.9%, 10.3%, and 9.4%, the highest being for the lowest ESR value. Correlation coefficients for the comparison between iSED and Westergren were 0.862 (Site-1) and 0.916 (Site-2). While proportional difference with a positive bias was revealed at Site-1, comparison at Site-2 showed both constant and proportional difference and a negligible negative bias. Higher correlation was obtained for samples with low than normal hematocrit. Comparison between iSED and TEST1 yielded a correlation coefficient of 0.986, constant and proportional difference, and positive bias. Carryover was 3.2%. CONCLUSION: This study proved the analytical validity of the iSED analyzer, despite minor discrepancies to the Westergren method that can be attributed to methodological differences.

Interplay of Coriolis effect with rheology results in unique blood dynamics on a compact disc.

We investigate the influence of rotational forces on blood dynamics in a microfluidic device. The special confluence of Coriolis force and blood rheology is brought forth by analyzing the flow at different hematocrit (volume fraction of red blood cells) levels and rotational speeds. We further study the effects of channel layout and alignment with regard to the axis of rotation to understand this intricate interplay. We provide a sound basis for efficient designing of a lab on a compact disc (lab on CD) platform by harnessing the effects of Coriolis force at relatively much lower rotational speeds, in sharp contrast with the reported findings where Coriolis effects have been considered to be effective only for exceptionally high rotational speeds. Our results show that over certain intermediate regimes of rotational speeds, the flow profiles for different hematocrit levels are noticeably different. This, in turn, could be harnessed as a possible diagnostic signature of the hematocrit (or equivalently, packed cell volume) level, without necessitating the deployment of chemical consumables, in an energy efficient paradigm.

Laboratory Evaluation of Linearity, Repeatability, and Hematocrit Interference With an Internet-Enabled Blood Glucose Meter.

BACKGROUND: In recent clinical trials, use of the MyGlucoHealth blood glucose meter (BGM) and electronic diary was associated with an unusual reporting pattern of glycemic data and hypoglycemic events. Therefore, the performance of representative BGMs used by the patients was investigated to assess repeatability, linearity, and hematocrit interference in accordance with regulatory guidelines. METHOD: Ten devices and 6 strip lots were selected using standard randomization and repeatability procedures. Venous heparinized blood was drawn from healthy subjects, immediately aliquoted and adjusted to 5 target blood glucose (BG) ranges for the repeatability and 11 BG concentrations for the linearity tests. For the hematocrit interference test, each sample within 5 target BG ranges was split into 5 aliquots and adjusted to hematocrit levels across the acceptance range. YSI 2300 STAT Plus was used as the laboratory reference method in all experiments. RESULTS: Measurement repeatability or precision was acceptable across the target BG ranges for all devices and strip lots with coefficient of variation (CV) between 3.4-9.7% (mean: 5.7%). Linearity was shown by a correlation coefficient of .991; however, a positive bias was seen for BG <100 mg/dL (86% measurements did not meet ISO15197:2015 acceptance criteria). Significant hematocrit interference (up to 20%) was observed for BG >100 mg/dL (ISO15197:2015 acceptance criteria: ±10%), while the results were acceptable for BG <100 mg/dL. CONCLUSIONS: The BGM met repeatability requirements but demonstrated a significant measurement bias in the low BG range. In addition, it failed the ISO15197:2015 criteria for hematocrit interference.

Comparative Accuracy Evaluation of a Blood Glucose Meter With Novel Hematocrit Correction Technology, With Three Currently Used Commercially Available Blood Glucose Monitoring Systems.

Hematocrit is known to influence glucose values obtained on some blood glucose meters, with bias observed especially at low and high hematocrit levels. We evaluated the performance of a meter with hematocrit correction technology alongside 3 other commercially available meters. Capillary blood samples from 100 subjects were analyzed in duplicate and compared to the plasma values obtained by reference laboratory analyzer. Bias, error grid, and sensitivity to hematocrit analyses were performed for each meter. Average percentage bias was similar for all meters, however the evaluated meter performed best with respect to error grid analysis, with 100% of values falling within the "no effect on clinical action" and "no risk" categories and did not display any hematocrit associated bias.

Correlation between sodium, potassium, hemoglobin, hematocrit, and glucose values as measured by a laboratory autoanalyzer and a blood gas analyzer.

INTRODUCTION: Blood gas analyzers can be alternatives to laboratory autoanalyzers for obtaining test results in just a few minutes. We aimed to find out whether the results from blood gas analyzers are reliable when compared to results of core laboratory autoanalyzers. MATERIALS AND METHODS: This retrospective, single-centered study examined the electronic records of patients admitted to the emergency department of a tertiary care teaching hospital between May 2014 and December 2017. Excluded from the study were patients under 18 years old, those lacking data, those who had any treatment before the laboratory tests, those whose venous gas results were reported more than 30 minutes after the blood sample was taken and for whom any of the laboratory tests were performed at a different time, and recurrent laboratory results from a single patient. RESULTS: Laboratory results were analyzed from a total of 31,060 patients. The correlation coefficients for sodium, potassium, hemoglobin, hematocrit, and glucose levels measured by a blood gas analyzer and a laboratory autoanalyzer were 0.725, 0.593, 0.982, 0.958, and 0.984, respectively; however, there were no good, acceptable agreement limits for any of the parameters. In addition, these results did not change according to the different pH stages (acidosis, normal pH and alkalosis). CONCLUSION: The two types of measurements showed a moderate correlation for sodium and potassium levels and a strong correlation for glucose, hemoglobin, and hematocrit levels, but none of the levels had acceptable agreement limits. Clinicians should be aware of the limitations of blood gas analyzer results.

Investigation of the Accuracy of 18 Marketed Blood Glucose Monitors.

OBJECTIVE: Cleared blood glucose monitors (BGMs) for personal use may not always deliver levels of accuracy currently specified by international and U.S. regulatory bodies. This study's objective was to assess the accuracy of 18 such systems cleared by the U.S. Food and Drug Administration representing approximately 90% of commercially available systems used from 2013 to 2015. RESEARCH DESIGN AND METHODS: A total of 1,035 subjects were recruited to have a capillary blood glucose (BG) level measured on six different systems and a reference capillary sample prepared for plasma testing at a reference laboratory. Products were obtained from consumer outlets and tested in three triple-blinded studies. Each of the three participating clinical sites tested a different set of six systems for each of the three studies in a round-robin. In each study, on average, a BGM was tested on 115 subjects. A compliant BG result was defined as within 15% of a reference plasma value (for BG ≥100 mg/dL [5.55 mmol/L]) or within 15 mg/dL (0.83 mmol/L) (for BG <100 mg/dL [5.55 mmol/L]). The proportion of compliant readings in each study was compared against a predetermined accuracy standard similar to, but more lenient than, current regulatory standards. Other metrics of accuracy included the overall compliance proportion; the proportion of extreme outlier readings differing from the reference value by >20%; modified Bland-Altman analysis including average bias, coefficient of variation, and 95% limits of agreement; and proportion of readings with no clinical risk as determined by the Surveillance Error Grid. RESULTS: The different accuracy metrics produced almost identical BGM rankings. Six of the 18 systems met the predetermined accuracy standard in all three studies, 5 systems met it in two studies, and 3 met it in one study. Four BGMs did not meet the accuracy standard in any of the three studies. CONCLUSIONS: Cleared BGMs do not always meet the level of analytical accuracy currently required for regulatory clearance. This information could assist patients, professionals, and payers in choosing products and regulators in evaluating postclearance performance.

Noninvasive hematocrit assessment for cardiovascular magnetic resonance extracellular volume quantification using a point-of-care device and synthetic derivation.

BACKGROUND: Calculation of cardiovascular magnetic resonance (CMR) extracellular volume (ECV) requires input of hematocrit, which may not be readily available. The purpose of this study was to evaluate the diagnostic accuracy of ECV calculated using various noninvasive measures of hematocrit compared to ECV calculated with input of laboratory hematocrit as the reference standard. METHODS: One hundred twenty three subjects (47.7 ± 14.1 years; 42% male) were prospectively recruited for CMR T1 mapping between August 2016 and April 2017. Laboratory hematocrit was assessed by venipuncture. Noninvasive hematocrit was assessed with a point-of-care (POC) device (Pronto-7® Pulse CO-Oximeter®, Masimo Personal Health, Irvine, California, USA) and by synthetic derivation based on the relationship with blood pool T1 values. Left ventricular ECV was calculated with input of laboratory hematocrit (Lab-ECV), POC hematocrit (POC-ECV), and synthetic hematocrit (synthetic-ECV), respectively. Statistical analysis included Wilcoxon signed-rank test, Bland-Altman analysis, receiver-operating curve analysis and intra-class correlation (ICC). RESULTS: There was no significant difference between Lab-ECV and POC-ECV (27.1 ± 4.7% vs. 27.3 ± 4.8%, p = 0.106), with minimal bias and modest precision (bias - 0.18%, 95%CI [- 2.85, 2.49]). There was no significant difference between Lab-ECV and synthetic-ECV (26.7 ± 4.4% vs. 26.5 ± 4.3%, p = 0.084) in subjects imaged at 1.5 T, although bias was slightly higher and limits of agreement were wider (bias 0.23%, 95%CI [- 2.82, 3.27]). For discrimination of abnormal Lab-ECV ≥30%, POC-ECV had good diagnostic performance (sensitivity 85%, specificity 96%, accuracy 94%, and AUC 0.902) and synthetic-ECV had moderate diagnostic performance (sensitivity 71%, specificity 98%, accuracy 93%, and AUC 0.849). POC-ECV had excellent test-retest (ICC 0.994, 95%CI[0.987, 0.997]) and inter-observer agreement (ICC 0.974, 95%CI[0.929, 0.991]). CONCLUSIONS: Myocardial ECV can be accurately and reproducibly calculated with input of hematocrit measured using a noninvasive POC device, potentially overcoming an important barrier to implementation of ECV. Further evaluation of synthetic ECV is required prior to clinical implementation.

Development of a diagnostic sensor for measuring blood cell concentrations during haemoconcentration.

BACKGROUND: HemoSep® is a commercial ultrafiltration and haemoconcentration device for the concentration of residual bypass blood following surgery. This technology is capable of reducing blood loss in cardiac and other types of "clean site" procedures, including paediatric surgery. Clinical feedback suggested that the device would be enhanced by including a sensor technology capable of discerning the concentration level of the processed blood product. We sought to develop a novel sensor that can, using light absorption, give an accurate estimate of packed cell volume (PCV). MATERIALS AND METHODS: A sensor-housing unit was 3D printed and the factors influencing the sensor's effectiveness - supply voltage, sensitivity and emitter intensity - were optimised. We developed a smart system, using comparator circuitry capable of visually informing the user when adequate PCV levels (⩾35%) are attained by HemoSep® blood processing, which ultimately indicates that the blood is ready for autotransfusion. RESULTS: Our data demonstrated that the device was capable of identifying blood concentration at and beyond the 35% PCV level. The device was found to be 100% accurate at identifying concentration levels of 35% from a starting level of 20%. DISCUSSION: The sensory capability was integrated into HemoSep's® current device and is designed to enhance the user's clinical experience and to optimise the benefits of HemoSep® therapy. The present study focused on laboratory studies using bovine blood. Further studies are now planned in the clinical setting to confirm the efficacy of the device.

Measurement of the hematocrit using paper-based microfluidic devices.

The quantification of blood cells provides critical information about a patient's health status. Sophisticated analytical equipment, such as hematology analyzers, have been developed to perform these measurements, but limited-resource settings often lack the infrastructure required to purchase, operate, and maintain instrumentation. To address these practical challenges, paper-based microfluidic devices have emerged as a platform to develop diagnostic assays specifically for use at the point-of-care. To date, paper-based microfluidic devices have been used broadly in diagnostic assays that apply immunoassay, clinical chemistry, and electrochemistry techniques. The analysis of cells, however, has been largely overlooked. In this communication, we demonstrate a paper-based microfluidic device that enables the controlled transport of red blood cells (RBCs) and the measurement of the hematocrit-the ratio of RBC packed cell volume to total volume of whole blood. The properties of paper, device treatment, and device geometry affect the overall extent and reproducibility of transport of RBCs. Ultimately, we developed an inexpensive (US$0.03 per device) thermometer-styled device where the distance traveled by RBCs is proportional to the hematocrit. These results provide a foundation for the design of paper-based microfluidic devices that enable the separation and detection of cells in limited-resource settings.

Point-of-Care Testing for Anaemia in Children Using Portable Haematocrit Meter: A Pilot Study from Southwest Nigeria and Implications for Developing Countries.

BACKGROUND: Prompt and accurate diagnosis is needed to prevent the untoward effects of anaemia on children. Although haematology analyzers are the gold standard for accurate measurement of haemoglobin or haematocrit for anaemia diagnosis, they are often out of the reach of most health facilities in resource-poor settings thus creating a care gap. We conducted this study to examine the agreement between a point-of-care device and haematology analyzer in determining the haematocrit levels in children and to determine its usefulness in diagnosing anaemia in resource-poor settings. METHODS: EDTA blood samples collected from participants were processed to estimate their haematocrits using the two devices (Mindray BC-3600 haematology analyzer and Portable Mission Hb/Haemotocrit testing system). A pairwise t-test was used to compare the haematocrit (PCV) results from the automated haematology analyzer and the portable haematocrit meter. The agreement between the two sets of measurements was assessed using the Bland and Altman method where the mean, standard deviation and limit of agreement of paired results were calculated. RESULTS: The intraclass and concordance correlation coefficients were 0.966 and 0.936. Sensitivity and specificity were 97.85% and 94.51% respectively while the positive predictive and negative predictive values were 94.79% and 97.73%. The Bland and Altman`s limit of agreement was -5.5-5.1 with the mean difference being -0.20 and a non-ignificant variability between the two measurements (p = 0.506). CONCLUSION: Haematocrit determined by the portable testing system is comparable to that determined by the haematology analyzer. We therefore recommend its use as a point-of-care device for determining haematocrit in resource-poor settings where haematology analyzers are not available.

Hematocrit analysis through the use of an inexpensive centrifugal polyester-toner device with finger-to-chip blood loading capability.

Hematocrit (HCT) measurements are important clinical diagnostic variables that help physicians diagnose and treat various medical conditions, ailments, and diseases. In this work, we present the HCT Disc, a centrifugal microdevice fabricated by a Print, Cut and Laminate (PCL) method to generate a 12-sample HCT device from materials costing <0.5 USD (polyester and toner or PeT). Following introduction from a drop of blood (finger stick), whole blood metering and cell sedimentation are controlled by centrifugal force, only requiring a CD player motor as external hardware and, ultimately, a cell phone for detection. The sedimented volume from patient blood in the HCT Disc was analyzed using a conventional scanner/custom algorithm for analysis of the image to determine a hematocrit value, and these were compared to values generated in a clinical laboratory, which correlated well. To enhance portability and assure simplicity of the HCT measurement, values from image analysis by a cell phone using a custom application was compared to the scanner. Fifteen samples were analyzed with cell phone image analysis system and were found to be within 4% of the HCT values determined in the clinical lab. We demonstrate the feasibility of the PeT device for HCT measurement, and highlight its uniquely low cost (<0.5 USD), speed (sample-to-answer <8 min), multiplexability (12 samples), low volume whole blood requirement (<3 µL), rotation speeds (<4000 rpm) needed for effective measurement as well as the direct finger-to-chip sample loading capability.

Measuring Hematocrit in Mice Injected with In Vitro-Transcribed Erythropoietin mRNA.

In vitro-transcribed (IVT) mRNA encoding therapeutic protein has the potential to treat a variety of diseases by serving as template for translation in the patient. To optimize conditions for such therapy, reporter protein-encoding mRNAs are usually used. One preferred reporter is erythropoietin (EPO), which stimulates erythropoiesis and leads to an increase in hematocrit. Measurement of hematocrit is a fast and reliable method to determine the potency of the in vitro-transcribed EPO mRNA. However, frequent blood draw from mice can increase hematocrit due to blood loss. Therefore, instead of using conventional hematocrit capillary tubes, we adapted glass microcapillaries for hematocrit measurement. Daily monitoring of mice can be accomplished by drawing less than 20 µL of blood, thus avoiding blood loss-related hematocrit increase. Due to the small volume of the withdrawn blood the hematocrit remains the same for mice injected with control mRNA, whereas significant hematocrit increase is measured between day 4 and 20 postinjection for those injected with pseudouridine-modified EPO mRNA. Following hematocrit measurement the microcapillaries are snapped easily to recover plasma for further analyses, including EPO measurement by ELISA.

A Novel, Nondestructive, Dried Blood Spot-Based Hematocrit Prediction Method Using Noncontact Diffuse Reflectance Spectroscopy.

Dried blood spot (DBS) sampling is recognized as a valuable alternative sampling strategy both in research and in clinical routine. Although many advantages are associated with DBS sampling, its more widespread use is hampered by several issues, of which the hematocrit effect on DBS-based quantitation remains undoubtedly the most widely discussed one. Previously, we developed a method to derive the approximate hematocrit from a nonvolumetrically applied DBS based on its potassium content. Although this method yielded good results and was straightforward to perform, it was also destructive and required sample preparation. Therefore, we now developed a nondestructive method which allows to predict the hematocrit of a DBS based on its hemoglobin content, measured via noncontact diffuse reflectance spectroscopy. The developed method was thoroughly validated. A linear calibration curve was established after log/log transformation. The bias, intraday and interday imprecision of quality controls at three hematocrit levels and at the lower and upper limit of quantitation (0.20 and 0.67, respectively) were less than 11%. In addition, the influence of storage and the volume spotted was evaluated, as well as DBS homogeneity. Application of the method to venous DBSs prepared from whole blood patient samples (n = 233) revealed a good correlation between the actual and the predicted hematocrit. Limits of agreement obtained after Bland and Altman analysis were -0.076 and +0.018. Incurred sample reanalysis demonstrated good method reproducibility. In conclusion, mere scanning of a DBS suffices to derive its approximate hematocrit, one of the most important variables in DBS analysis.

Point-of-Care Hemoglobin/Hematocrit Testing: Comparison of Methodology and Technology.

OBJECTIVE: Point-of-care (POC) testing allows rapid assessment of hemoglobin (Hgb) and hematocrit (Hct) values. This study compared 3 POC testing devices--the Radical-7 pulse oximeter (Radical-7, Neuchȃtel, Switzerland), the i-STAT (Abbott Point of Care, Princeton, NJ), and the GEM 4000 (Instrumentation Laboratory, Bedford, MA)--to the hospital reference device, the UniCel DxH 800 (Beckman Coulter, Brea, CA) in cardiac surgery patients. DESIGN: Prospective study. SETTING: Tertiary care cardiovascular center. PARTICIPANTS: Twenty-four consecutive elective adult cardiac surgery patients. INTERVENTIONS: Hgb and Hct values were measured using 3 POC devices (the Radical-7, i-STAT, and GEM 4000) and a reference laboratory device (UniCel DxH 800). Data were collected simultaneously before surgery, after heparin administration, after heparin reversal with protamine, and after sternal closure. Data were analyzed using bias analyses. POC testing data were compared with that of the reference laboratory device. MEASUREMENTS AND MAIN RESULTS: Hgb levels ranged from 6.8 to 15.1 g/dL, and Hct levels ranged from 20.1% to 43.8%. The overall mean bias was lowest with the i-STAT (Hct, 0.22%; Hgb 0.05 g/dL) compared with the GEM 4000 (Hct, 2.15%; Hgb, 0.63 g/dL) and the Radical-7 (Hgb 1.16 g/dL). The range of data for the i-STAT and Radical-7 was larger than that with the GEM 4000, and the pattern or slopes changed significantly with the i-STAT and Radical-7, whereas that of the GEM 4000 remained relatively stable. The GEM 4000 demonstrated a consistent overestimation of laboratory data, which tended to improve after bypass and at lower Hct/Hgb levels. The i-STAT bias changed from overestimation to underestimation, the latter in the post-cardiopulmonary bypass period and at lower Hct/Hgb levels. By contrast, the Radical-7 biases increased during the surgical procedure and in the lower ranges of Hgb. CONCLUSION: Important clinical differences and limitations were found among the 3 POC testing devices that should caution clinicians from relying on these data as sole determinants of when or when not to perform transfusion in patients. Even though a low bias might support the use of POC data, further analysis of the bias plots demonstrates pattern changes during the surgical procedure and across the range of Hct/Hgb data.