ABSTRACT
INTRODUCTION: The Thai National Guidelines for Hemostatic Laboratory Testing were established in 2018. The guidelines recommend that the 20-min whole blood clotting time (20WBCT) method be used to diagnose/monitor snake bites. The aim of this study was to survey members of the Thailand National External Quality Assessment Scheme (NEQAS) for Blood Coagulation to investigate the use of 20WBCT testing compared between the 2021 post-guideline and 2007 pre-guideline periods. METHODS: In July 2021, questionnaires were sent from the Faculty of Medicine Siriraj Hospital, Mahidol University to 521 Thailand NEQAS for Blood Coagulation member laboratories to survey their WBCT practices. Current WBCT practices were compared with pre-guideline WBCT practices, and chi-square test (x2) was used to test for differences between groups. RESULTS: Ninety-seven (18.6%) of 521 surveys were returned. Seventy-one laboratories (73.2%) reported knowing about 20WBCT from the Thai national guidelines. The reported average frequency of overall WBCT testing in 2021 was 12.4 times/month. The proportion of laboratories that reported using the 20WBCT test increased from 2.0% in 2007 to 46.4% in 2021 (p < 0.001), and the indications for performing WBCT were virtually unchanged from 2007 to 2021. The proportion of laboratories that reported having problems with WBCT testing decreased from 32.7% in 2007 to 16.5% in 2021. CONCLUSION: Despite our findings that almost three-quarters of respondent laboratories reported knowing about 20WBCT testing from the WBCT guidelines, and that WBCT-specific problems decreased significantly from 2007 to 2021, more work and training is needed to improve WBCT guideline dissemination, understanding, and adherence in Thailand.
Subject(s)
Blood Coagulation , Humans , Thailand , Whole Blood Coagulation Time/standards , Surveys and Questionnaires , Quality Assurance, Health Care , Practice Guidelines as Topic , Laboratories, Clinical/standardsABSTRACT
In October 2009, the U.S. Pharmacopoeia (USP) changed the monograph for heparin to bring USP units in line with international units for heparin. The result was a 10% decrease in potency as measured by in vitro laboratory tests. This decrease led to questions regarding dosing guidelines. There existed a need for an in vivo study to determine the practical changes that may need to be implemented in regard to heparin administration for cardiopulmonary bypass in the clinical setting. A retrospective study was conducted to determine the heparin dose administered and the corresponding effect on patients undergoing coronary artery bypass grafting surgery using cardiopulmonary bypass. The study compared the heparin dose requirements and activated clotting time (ACT) results using the heparin before and after the USP changes. An analysis of the data was performed to determine the increased heparin dose required to achieve the same effect as before the USP change. This new heparin dosing protocol was instituted at Concord Hospital, Concord, NH. A prospective study was then preformed to verify the effects of the dosing change. In the new heparin group, the postheparin ACT fell by 9.1% (p = .028) and the patients achieving an ACT > 479 seconds fell by 12.8% as compared with the old heparin group. After adjustment of the loading dose calculation for heparin, the prospective study demonstrated the postheparin ACT (p = .684) and the percentage of patients achieving an ACT > 479 seconds (p = 1.000) to be similar to the values obtained before the USP change. An increase of the loading dose of approximately 12% is needed to achieve the patient effects seen before the UPS change.
Subject(s)
Cardiopulmonary Bypass/statistics & numerical data , Cardiopulmonary Bypass/standards , Heparin/blood , Heparin/standards , International System of Units , Whole Blood Coagulation Time/statistics & numerical data , Whole Blood Coagulation Time/standards , Anticoagulants/blood , Anticoagulants/standards , Humans , Reference Standards , United StatesABSTRACT
OBJECTIVE: To compare the activated coagulation times (ACTs) measured with the blood-saving kaolin i-STAT 1 ACT technique (Abbott Point of Care Inc, Princeton, NJ) with ACTs obtained from the widely used ACTR II device (Medtronic, Inc, Minneapolis, MN) in children undergoing cardiac surgery. DESIGN: A prospective, observational single-center study. PARTICIPANTS: Forty-four pediatric cardiac surgery patients. INTERVENTION: Surgery was performed with cardiopulmonary bypass (CPB) necessitating heparinization. METHODS AND MAIN RESULTS: ACTs measured on the i-STAT 1 device (2 × 95 µL) were compared with those obtained from the Medtronic ACTR II device (2 × 0.5 mL). Blood samples were drawn before, during, and after heparinization for CPB and paired for statistical analysis. The 2 techniques were compared using simple and multiregression analyses and the Bland-Altman method. In total, 179 intrarater and 142 interrater data pairs were analyzed. The intrarater reliability of the 2 devices was good, with a mean bias and limits of agreement of +2.0 and -55.5/+59.5 seconds for the Medtronic ACTR II and +0.5 and -59.9/+60.9 seconds for the i-STAT 1. An interrater reliability analysis of the mean of simultaneously measured ACT of the Medtronic ACTR II and both i-STAT 1 devices yielded a mean bias of -5.3 seconds and limits of agreement of -210.1/+199.5 seconds. A comparison of the higher of the paired ACT values from both devices showed similar results. After the removal of heparin, the i-STAT 1's ACT values became significantly lower than those measured on the Medtronic ACTR II (p < 0.001). Simple and multiregression analyses revealed that base excess independently influenced the mean bias of the ACT values from the Medtronic ACTR II (p = 0.037) and i-STAT 1 devices (p = 0.036). CONCLUSION: The kaolin i-STAT 1 ACT technique agreed well with the Medtronic ACTR II technique during the nonheparinized phase that preceded CPB. The overall agreement between the ACT obtained from the 2 devices was poor. The routine use of i-STAT 1 measured ACT values cannot be recommended as a reliable alternative to the Medtronic ACTR II.
Subject(s)
Anesthesia/standards , Blood Coagulation , Cardiopulmonary Bypass/standards , Monitoring, Intraoperative/standards , Whole Blood Coagulation Time/standards , Adolescent , Age Factors , Anesthesia/methods , Cardiac Surgical Procedures/standards , Child , Child, Preschool , Female , Humans , Infant , Male , Monitoring, Intraoperative/instrumentation , Monitoring, Intraoperative/methods , Partial Thromboplastin Time/instrumentation , Partial Thromboplastin Time/methods , Partial Thromboplastin Time/standards , Prospective Studies , Whole Blood Coagulation Time/instrumentation , Whole Blood Coagulation Time/methodsABSTRACT
OBJECTIVE: To compare the kaolin-activated coagulation time (K-ACT) to the MAX-ACT for monitoring anticoagulation with bivalirudin in patients undergoing hybrid off-pump coronary artery revascularization procedures. DESIGN: A prospective, observational study. SETTING: A cardiac surgical operating room of a university-affiliated hospital. PARTICIPANTS: Twelve patients undergoing off-pump coronary artery bypass graft surgery and percutaneous coronary intervention during the same procedure anticoagulated with bivalirudin to a target K-ACT of >300 seconds. INTERVENTION: At baseline and at frequent intervals during anticoagulation, K-ACT and MAX-ACT assays were run contemporaneously, and the pairs of results were analyzed with descriptive statistics, by correlation analysis, and with Bland-Altman analysis. MEASUREMENTS AND MAIN RESULTS: The MAX-ACT and K-ACT assays were highly correlated, but the MAX-ACT assay consistently reported significantly lower ACT values compared with the K-ACT. The mean bias (K-ACT minus MAX-ACT) was 94 seconds (limits of agreement, 51-138 seconds). CONCLUSION: To maximize patient safety, centers using bivalirudin for anticoagulation during cardiac surgical procedures need to be aware of the different performance characteristics of ACT assay subtypes.
Subject(s)
Coronary Artery Bypass, Off-Pump , Minimally Invasive Surgical Procedures , Partial Thromboplastin Time/standards , Peptide Fragments/therapeutic use , Whole Blood Coagulation Time/standards , Blood Coagulation/drug effects , Blood Coagulation/physiology , Coronary Artery Bypass, Off-Pump/methods , Female , Hirudins/pharmacology , Humans , Male , Minimally Invasive Surgical Procedures/methods , Peptide Fragments/pharmacology , Postoperative Complications/blood , Postoperative Complications/prevention & control , Prospective Studies , Recombinant Proteins/pharmacology , Recombinant Proteins/therapeutic useABSTRACT
BACKGROUND: Hemostasis management has evolved to include sophisticated point-of-care systems that provide individualized dosing through heparin concentration-based anticoagulation. The Hepcon HMS Plus system (Medtronic, Minneapolis, MN) estimates heparin dose, activated clotting time (ACT), and heparin dose response (HDR). However, the accuracy of this test has not been systematically evaluated in large cohorts. METHODS: We examined institutional databases for all patients who underwent cardiac surgery with cardiopulmonary bypass (CPB) at our institution from February 2005 to July 2008. During this period, the Hepcon HMS Plus was used exclusively for assessment of heparin dosing and coagulation monitoring. Detailed demographic, surgical, laboratory, and heparin dosing data were recorded. ACT, calculated and measured HDR, and heparin concentrations were recorded. Performance of the Hepcon HMS Plus was assessed by comparison of actual and target ACT values and calculated and measured HDR. RESULTS: In 3880 patients undergoing cardiac surgery, heparin bolus dosing to a target ACT resulted in wide variation in the postheparin ACT (r(2) = 0.03). The postheparin ACT did not reach the target ACT threshold in 7.4%(i.e., when target ACT was 300 s) and 16.9% (i.e., when target ACT was 350 s) of patients. Similarly, the target heparin level calculated from the HDR did not correlate with the postbolus heparin level, with 18.5% of samples differing by more than 2 levels of the assay. Calculated and measured HDR were not linearly related at any heparin level. CONCLUSIONS: The Hepcon HMS Plus system poorly estimates heparin bolus requirements in the pre-CPB period. Further prospective studies are needed to elucidate what constitutes adequate anticoagulation for CPB and how clinicians can reliably and practically assess anticoagulation in the operating room.
Subject(s)
Anticoagulants/administration & dosage , Cardiac Surgical Procedures/standards , Hemostatic Techniques/standards , Heparin/administration & dosage , Aged , Dose-Response Relationship, Drug , Female , Hemostatic Techniques/instrumentation , Humans , Male , Middle Aged , Predictive Value of Tests , Reproducibility of Results , Retrospective Studies , Treatment Failure , Whole Blood Coagulation Time/standardsABSTRACT
Objective This study compared the activated clotting time (ACT) measured using the Hemochron Jr. Signature (HACT) with the ACT measured using the Medtronic ACT Plus (MACT) during cardiopulmonary bypass (CPB) with acute normovolemic haemodilution (ANH) in patients undergoing cardiac surgery. Methods The ACT was checked at baseline with both devices after inducing anaesthesia, and 400 to 800 mL of whole blood was withdrawn to induce moderate ANH. Before initiating CPB, a 300-IU/kg bolus dose of heparin was administered to maintain the HACT at >400 s; protamine was later given to reverse the anticoagulation. The ACT was checked using both devices at baseline, during heparinisation, and after protamine administration. Results In total, 106 pairs of samples from 29 patients were analysed. The ACT showed a good correlation between the two devices (r = 0.956). However, Bland-Altman analysis showed that the MACT was higher, particularly at baseline and during heparinisation. Multiple regression analysis showed that the blood glucose concentration significantly influenced the differences between the two ACT devices. Conclusions The HACT was lower than the MACT during CPB with ANH in patients undergoing cardiac surgery. Clinicians should be cautious when using each ACT device within generally accepted reference ACT values.
Subject(s)
Automation, Laboratory/instrumentation , Cardiopulmonary Bypass , Hemodilution/methods , Phlebotomy/methods , Whole Blood Coagulation Time/instrumentation , Aged , Anesthesia, General , Anticoagulants/therapeutic use , Artifacts , Automation, Laboratory/standards , Blood Glucose/metabolism , Blood Viscosity , Female , Heparin/therapeutic use , Heparin Antagonists/therapeutic use , Humans , Male , Middle Aged , Protamines/therapeutic use , Regression Analysis , Whole Blood Coagulation Time/standardsABSTRACT
Hirudin, a direct thrombin inhibitor, has potential advantages over indirect thrombin inhibitors and is increasingly used in clinical settings. There are, however, large variations in individual responses to this drug and no recognized clinical laboratory tests used to monitor its anticoagulant effects. We evaluated the use of the thromboelastograph, a common clinical coagulation instrument, to monitor the effects of hirudin in vitro. We developed a novel, whole blood clotting assay that utilizes the tissue factor stimulating properties of mercuric ion to measure the anticoagulant potential of therapeutic doses of hirudin. At doses equivalent to those found in the therapeutic range, the thromboelastograph was capable of showing significant changes when compared with control and different concentrations of hirudin (P < 0.05). A linear relationship was observed between increasing concentrations of recombinant hirudin and clotting times. In conclusion, the use of this test system warrants further investigation for monitoring hirudin.
Subject(s)
Blood Coagulation Tests/methods , Drug Monitoring/methods , Hirudins/administration & dosage , Blood Coagulation Tests/standards , Dose-Response Relationship, Drug , Drug Monitoring/standards , Humans , Mercury/pharmacology , Thrombelastography/methods , Thrombelastography/standards , Thromboplastin/drug effects , Whole Blood Coagulation Time/methods , Whole Blood Coagulation Time/standardsABSTRACT
The 20-minute whole blood clotting test (WBCT20) is used as a bedside diagnostic test for coagulopathic snake envenoming. We aimed to assess the performance of the WBCT20 in diagnosis of venom induced consumption coagulopathy (VICC) in Russell's viper envenoming. Adult patients admitted with suspected snake bites were recruited from two hospitals. WBCT20 and prothrombin time (PT) test were performed on admission. WBCT20 was done by trained clinical research assistants using 1 ml whole blood in a 5 ml borosilicate glass tube with a 10 mm internal diameter. The PT was measured by a semi-automated coagulation system and international normalised ratio (INR) calculated. VICC was defined as present if the INR was >1.4. The diagnostic utility of WBCT20 was determined by calculating the sensitivity and specificity of the WBCT20 on admission for detecting VICC. There were 987 snake bites where both WBCT20 and PT were done on admission samples. This included 79 patients (8 %) with VICC. The WBCT20 was positive in 65/79 patients with VICC (sensitivity 82 %; 95 % confidence interval [CI]: 72-90 %) and was falsely positive in 13/908 with no coagulopathy. The WBCT20 was negative in 895/908 snake bites with no coagulopathy (specificity: 98 % 95 % CI: 97-99 %) and was falsely negative in 14/79 with VICC. Using trained clinical staff, the WBCT20 test had a relatively good sensitivity for the detection of VICC, but still missed almost one fifth of cases where antivenom was potentially indicated.
Subject(s)
Blood Coagulation , Daboia , Disseminated Intravascular Coagulation/diagnosis , Snake Bites/diagnosis , Viper Venoms , Whole Blood Coagulation Time , Adolescent , Adult , Aged , Aged, 80 and over , Animals , Antivenins/therapeutic use , Disseminated Intravascular Coagulation/blood , Disseminated Intravascular Coagulation/drug therapy , False Negative Reactions , False Positive Reactions , Female , Humans , Male , Middle Aged , Predictive Value of Tests , Prospective Studies , Prothrombin Time , Reproducibility of Results , Snake Bites/blood , Sri Lanka , Time Factors , Whole Blood Coagulation Time/standards , Young AdultABSTRACT
This is the first study to identify normal whole-blood clotting times in various plastic containers and to identify the effect of the addition of various concentrations of Pseudechis australis (Mulga snake) venom on the clotting time in glass and plastic. Polycarbonate was identified as a potential alternative to glass as a testing container owing to a whole-blood clotting time within acceptable limits for a bedside test (mean 29.5 min) and equivalent performance to glass in the presence of P. australis venom. Other plastic containers (such as polypropylene and polyethylene) were found to be unsuitable owing to very prolonged clotting times (>60 min) or impaired performance in the presence of venom. Overall, owing to the variation between the performance of different plastics and the difficulty in differentiating between them, plastic containers cannot be recommended as an alternative to glass when performing the whole-blood clotting test for envenomed patients.
Subject(s)
Blood Coagulation Tests/instrumentation , Blood Coagulation/drug effects , Glass/standards , Plastics/standards , Snake Venoms/pharmacology , Whole Blood Coagulation Time/instrumentation , Analysis of Variance , Blood Coagulation Tests/standards , Dose-Response Relationship, Drug , Humans , Pilot Projects , Whole Blood Coagulation Time/standardsABSTRACT
BACKGROUND: The objective of the present study was to evaluate the efficacy of monitoring activated coagulation time (ACT) during carotid endarterectomy (CEA) in reducing surgical risks and complications. METHODS: A total of 175 consecutive patients who had CEA between July 2002 and January 2004 were studied. Activated coagulation time was monitored during the procedure in all patients. The results were compared with the data reported in the literature, and with those obtained in 2 previous series, totaling 1924 patients treated at the same service before the use of ACT. RESULTS: Only 4 of the 175 patients had cerebral ischemia, with 3 of them almost completely recovering during hospitalization. Significant morbidity was 0.6% and mortality was 0.6%. No statistically significant difference in the incidence of cerebral ischemia or death was observed between symptomatic and asymptomatic patients. In the 2 previous series used for comparison, operated by the same author, we found 0.7% and 0.8% of significant morbidity and 1.4% and 2.6% of mortality, respectively. Most series in the literature have shown a higher significant morbidity than the present one, mainly in symptomatic patients. The incidence of hematoma in the present series was 5.7%, only 3 (1.7%) of them being significant. No increase in the frequency of hematomas was observed in cases where heparin was not reversed or in those using a shunt. In the 2 other previous series, the incidence of hematomas was 1.5% and 3.6%. CONCLUSIONS: Activated coagulation time monitoring during CEA was effective in evaluating the level of heparinization of patients during surgery and the immediate postoperative period. The comparison of the present series with the literature and with the previous series of the same service, before the use of ACT, permits also to conclude that the control of the level of heparinization seems to reduce the risk of perioperative and immediate postoperative ischemia. In addition, ACT monitoring also seems to be effective in diminishing the risk of postoperative cervical hematoma.
Subject(s)
Endarterectomy, Carotid/methods , Postoperative Hemorrhage/etiology , Postoperative Hemorrhage/prevention & control , Adult , Aged , Aged, 80 and over , Brain Ischemia/etiology , Brain Ischemia/physiopathology , Brain Ischemia/prevention & control , Carotid Arteries/pathology , Carotid Arteries/physiopathology , Carotid Arteries/surgery , Endarterectomy, Carotid/adverse effects , Endarterectomy, Carotid/mortality , Female , Hematoma/etiology , Hematoma/physiopathology , Hematoma/prevention & control , Heparin/adverse effects , Heparin/therapeutic use , Humans , Male , Middle Aged , Monitoring, Physiologic/methods , Monitoring, Physiologic/standards , Postoperative Hemorrhage/physiopathology , Time Factors , Whole Blood Coagulation Time/methods , Whole Blood Coagulation Time/standardsABSTRACT
Point of care testing (POCT) must comply with regulatory requirements according to standard EN ISO 22870, which identify biologists as responsible for POCT. Activated clotting time (ACT) is mandatory to monitor on whole blood, anticoagulation achieved by unfractionated heparin during cardiopulmonary bypass (CPB) or cardiac catheterization. This test has no equivalent in the laboratory. With the aim to help the multidisciplinary groups for POCT supervision when they have to analyse the wish of medical departments to use ACT and to help the biologists to be in accordance with the standard, we present the guidelines of the GEHT (Groupe d'étude d'hémostase et thrombose) subcommittee "CEC et Biologie délocalisée" for the certification of ACT. These guidelines are based on the SFBC guidelines for the certification of POCT and on the analysis of the literature to ascertain the justification of clinical need and assess the analytical performance of main analyzers used in France, as well as on a survey conducted with French and Belgian biologists.
Subject(s)
Blood Coagulation , Certification , Monitoring, Intraoperative/methods , Monitoring, Intraoperative/standards , Thrombosis/blood , Accreditation , Cardiac Surgical Procedures/instrumentation , Cardiac Surgical Procedures/methods , Cardiac Surgical Procedures/standards , France , Hemostasis , Humans , Monitoring, Intraoperative/instrumentation , Reference Standards , Thrombosis/diagnosis , Whole Blood Coagulation Time/instrumentation , Whole Blood Coagulation Time/standardsABSTRACT
Historically, it has been difficult for hospitals to change methods for activated clotting time (ACT) testing because of differences in ACT values obtained with different instruments, wide differences in target ranges used in different procedures, and the difficulty of performing crossover studies at the bedside in critical care situations. There are limited published data comparing the i-STAT (Abbott Point of Care, Princeton, NJ) kaolin ACT with the Medtronic ACT Plus (Medtronic, Minneapolis, MN). The i-STAT system can perform ACT testing in addition to testing of a number of critical care analytes and may offer potential advantages over other ACT analyzers. Comparison of ACT values on 121 simultaneous split-sample tests yielded an R(2) of 0.88 with i-STAT = 0.79 Medtronic + 72.0. The Pearson correlation was R = 0.94, indicating statistically significant correlation between the 2 methods. Based on this comparison, we were able to implement the i-STAT ACT throughout our institution without changing target ranges for any individual procedure.
Subject(s)
Whole Blood Coagulation Time/standards , Academic Medical Centers , Blood Coagulation , Cardiovascular Surgical Procedures , Diatomaceous Earth , Humans , Kaolin , Reference Values , Whole Blood Coagulation Time/instrumentationABSTRACT
INTRODUCTION: Lower low-molecular-weight heparins are being developed to improve on the safety and efficacy of antithrombotic therapy. Semuloparin and bemiparin are two depolymerized heparins produced by distinct manufacturing processes. The objective of this investigation was to determine whether a common standard could be used to define their potency. MATERIALS AND METHODS: Activities were compared using typical clinical coagulation assays and pharmacological assays required for potency assessment. RESULTS: The activity of semuloparin and bemiparin was comparable in FXa-based assays (anti-FXa, Heptest). However, bemiparin produced a stronger effect in the aPTT, ACT and anti-thrombin assays. Assessment of the parallelism of the concentration-response curves indicated that bemiparin and semuloparin are not equivalent in terms of anti-FIIa activity. Bemiparin had a stronger inhibitory effect on thrombin induced platelet aggregation, and a stronger interaction with HIT antibodies. CONCLUSIONS: These data demonstrate that depolymerized heparins can exhibit a range of biologic activities making them unique agents. Pharmacopoeial parameters such as anti-IIa and anti-Xa potency and molecular weight are insufficient to characterize such agents.
Subject(s)
Blood Coagulation Tests/standards , Blood Coagulation/drug effects , Fibrinolytic Agents/pharmacology , Heparin, Low-Molecular-Weight/pharmacology , Platelet Function Tests/standards , Autoantibodies/metabolism , Dose-Response Relationship, Drug , Factor Xa Inhibitors , Fibrinolytic Agents/chemistry , Fibrinolytic Agents/immunology , Heparin, Low-Molecular-Weight/chemistry , Heparin, Low-Molecular-Weight/immunology , Humans , Molecular Structure , Molecular Weight , Partial Thromboplastin Time/standards , Platelet Aggregation/drug effects , Platelet Factor 4/immunology , Prothrombin/antagonists & inhibitors , Reference Standards , Structure-Activity Relationship , Thrombin/metabolism , Whole Blood Coagulation Time/standardsSubject(s)
Cardiac Catheterization/nursing , Coronary Artery Disease/blood , Coronary Artery Disease/therapy , Device Removal/nursing , Femoral Artery/surgery , Cardiac Catheterization/standards , Clinical Protocols , Device Removal/adverse effects , Device Removal/standards , Fibrinolytic Agents/therapeutic use , Hemorrhage/blood , Hemorrhage/etiology , Hemorrhage/nursing , Hemorrhage/prevention & control , Hemostatic Techniques/nursing , Hemostatic Techniques/standards , Humans , Platelet Aggregation Inhibitors/therapeutic use , Whole Blood Coagulation Time/nursing , Whole Blood Coagulation Time/standardsABSTRACT
BACKGROUND: Accurate control of heparin anticoagulation is necessary during all stages of cardiopulmonary bypass (CPB). The activated clotting time, first described by Hattersley in 1966, is mostly used for determination of anticoagulation. Either celite or kaolin are used as activators. An ACT value of 480 sec is proposed to be the safe minimum level for anticoagulation during CPB. This study was designed to determine if the activated coagulation time (ACT) values of each analyser separately are repeatable, and to determine whether there exists a significant difference in ACT values measured by three different analysers: the GEM PCL (Instrumentation Laboratory), the Hemochron 801 (International Technidyne Corporation) and the ACT II Automated Coagulation Timer (Medtronic). METHODS: All patients underwent cardiovascular surgical procedures requiring heparinisation (200-300 IU/kg). Blood samples for the measurement of the ACT were taken from all patients before and after heparinisation, during CPB, and after protamine administration. All samples were measured in duplicate with the three different analysers. To compare the activated clotting time data, the method described by Bland and Altman was used. The Pearson correlation coefficient was used to determine whether the differences were related to the average ACTs. p-Values <0.05 were considered statistically significant. RESULTS: The results showed that the three tested ACT analysers met the requirements of repeatability. The mean differences and standard deviations of the ACT values measured with the GEM PCL, the Hemochron 801, and the ACT II analyser were, respectively, -8.78 +/- 37.61, -19.77 +/- 68.82, and -6.23 +/- 39.21, with p-values=0.177, 0.081 and 0.384, respectively. The Pearson correlation coefficients were too low (-0.012, -0.221 and -0.241, respectively) to show any correlation between the differences and the means. The ACT values measured with the Hemochron 801 were not significantly different from the ACT values measured with the ACT II analyser: deltaACT =-34.09 +/- 146.68, with p=0.132. However, the GEM PCL did not agree with the Hemochron 801: deltaACT= -80.2 +/- 143.06, with p=0.001, or the ACT II analyser: deltaACT= -119.13 +/- 138.51, with p<0.001. A rather strong correlation was evident between the differences and the means measured with the GEM PCL compared with the Hemochron 801 (r=0.68) and the ACT II analyser (r=0.76). CONCLUSIONS: All analysers used celite or kaolin as activator. However, it was evident that the ACT measurements depended also on the analyser that had been chosen. A precaution that ACT values could not always be interpreted in the same way seems to be necessary.
Subject(s)
Monitoring, Physiologic/instrumentation , Whole Blood Coagulation Time/instrumentation , Autoanalysis/instrumentation , Autoanalysis/standards , Cardiopulmonary Bypass , Heparin/adverse effects , Heparin/therapeutic use , Humans , Point-of-Care Systems/standards , Reproducibility of Results , Sensitivity and Specificity , Whole Blood Coagulation Time/standards , Whole Blood Coagulation Time/statistics & numerical dataABSTRACT
An automated procedure for determination of clotting time in whole blood was validated by direct comparison with the reference method, visual clotting time determination. The procedure was based on a 10 Hz free oscillation rheometer (FOR) of our design, the ReoRox 4. Recalcified citrated blood samples (n = 30), clotting in the range 4 to 20 min, were used in the validation. Every 30 s of the analysis, as the change in stiffness (deltaG*) of the sample was monitored by FOR, the sample cup was shortly removed from the FOR and its contents inspected for first signs of clotting, i.e. visual clotting time determination. Various FOR clotting criteria were attempted. Best correlation to visual clotting time was found when deltaG* reached 0.01 Pa, which yielded linear regression slope, intercept and r2 of 0.98, 0.09 min and 0.98, respectively. For comparison, six plasma samples were analyzed in the same way and gave almost the same results. The accuracy of the FOR determinations was checked by also analyzing, in parallel, portions of the sample with a conventional oscillation rheometer, a Bohlin VOR. The rationale is given for preferring deltaG* over G* as a FOR monitoring function in coagulation tests and for including median filtration of the primary FOR data. An extension of the FOR theory to include deltaG* and evidence in support of inhomogeneous blood clotting are also given.