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Implementing a standardized POCT coagulation system.

In choosing the best point of care system for a facility, laboratorians must validate precision and accuracy of all new assays, ensure compliance with the CLIA regulations, and most importantly, run comparative studies of old and new instrumentation to gain acceptance by all end users.

Standardizing coagulation point of care testing (POCT) has become an increasingly complex task that involves a coordinated effort between administrators, laboratorians, and clinicians. In addition to selecting a single test system, individuals responsible for system implementation must ensure all tests are precise and accurate, and that they adhere to the CLIA regulations. Successful implementation also hinges on getting all employees involved in this testing to accept the new system as clinically reliable.

Recently, laboratory staff at Baptist Memorial Hospital East (Memphis, TN) selected the Hemochron Jr. Signature as its new coagulation system. While differences between this system and our previous instrumentation were anticipated, each hospital group involved in this area of testing had concerns, all of which had to be addressed prior to final execution of the new equipment. A scientific presentation of comparative data compiled at our facility helped end users to accept this new testing as a valuable addition to our department.

Following is a comprehensive account of how laboratorians from a large hospital made the transition from old to new point of care coagulation instrumentation.

Out with the old, in with the new

Since the mid 1980s, laboratory employees at Baptist Memorial Hospital East have used the Hemochron Activated Clotting Time (ACT) to monitor heparinization during cardiac catheterization and open heart surgery as well as to determine the best time for femoral sheath removal in the critical care unit (see "The importance of the ACT test," page 32). Last year, our pathology department decided to evaluate the feasibility of replacing its older Hemochron models (401 and 801) with the Hemochron Jr. Signature Analyzer.

The first automated Hemochron ACT instrumentation was developed in 1970. Bedside use of this standard system provides a rapid, reproducible, and reliable way to maintain a stable, steady state of heparin anticoagulation during critical extracorporeal and invasive procedures. [1] To run a test on this system, 2 ml of a fresh whole blood sample is placed in an ACT test tube, and the start button is pressed. The sample is shaken vigorously back and forth 10 times and placed in the instrument test well. When the test is completed, the instrument sounds an audible beep.

Alternatively, the Signature is a microsample system that performs many of the same assays as the standard test tube system. Before drawing a fresh whole blood sample for the Signature, however, the ACT+ cuvette is inserted into the analyzer to prewarm. Once the analyzer display reads "ADD SAMPLE ... PRESS START," the instrument allots five minutes for sample collection. A drop of blood is then added to the center well of the cuvette (flush to the top), and the start button is pressed. Sample measurement and mixing are performed automatically. Again, the instrument sounds an audible beep to indicate test completion.

Our pathology department's decision to compare old and new systems, had nothing to do with dissatisfaction with the older units. Rather, it was determined the hospital needed new ACT monitoring equipment to support additional test requests from perfusionists in the operating rooms and from clinicians working in the cardiac catheterization areas. Also, our pathology staff felt it was imperative we bring on board instrumentation 1) that had data management capabilities to ensure CLIA compliance, and 2) that wasn't as operator dependent as our traditional testing.

With these criteria in mind, the Signature became an extremely appealing option. For instance, its data management capabilities allow tracking of patient and operator identification numbers as well as QC results. Requiring the use of an instrument keypad to enter all ID numbers, this system enables laboratories to meet the regulations that mandate matching patient results to the particular instrument used. The automatic date and time stamp accompanying each result further supports adherence to these regulations. What's more, combining this built-in database with the ability to print/download reduces transcription errors and simplifies compliance with institutional QA policies.

The Signature also is not as operator-dependent as the test tube system, reducing the time required for training and simplifying routine proficiency assessment. User training programs are simplified as well due to the reduced sample size required for this system combined with the removal of sample shaking to initiate coagulation activation. These factors, combined with the historical satisfaction with the Hemochron brand, gave our department the confidence it needed to seriously consider replacing our test tube system with a microsystem.

Comparative evaluations

Before implementing the new equipment, all laboratorians who perform ACT tests in our facility were given the opportunity to run side-by-side evaluations of the old and new systems. These personnel include perfusionists involved in cardiac surgery requiring cardiopulmonary bypass, cardiovascular nurses in the cardiac catheterization laboratory, and nurses in the cardiovascular critical care unit.

Comparative evaluations were performed in the laboratory and in the clinical settings in which ACT is used. Before initiating any evaluation, we reviewed the Hemochron Jr. ACT+, DirectCheck whole blood control package inserts, and the Hemochron Jr. Signature operator's manual. All end users were instructed in the use of the new instrumentation and in its QC requirements, the latter of which mandates using two levels of electronic QC on each eight-hour shift the instrument is used to test instrument functionality. The test cuvettes were challenged with two levels of liquid QC (DirectCheck).

Our first analysis involved determining the normal range for our facility using 20 normal volunteer donors. From among these volunteers, 16 samples were tested with three different ACT tests (Celite-activated test tubes, kaolin-activated test tubes, and ACT+ cuvettes). An additional four samples were tested with only the celite tube and the cuvette. As expected, analysis of variance (ANOVA) revealed statistical differences between the three systems (P = 0.004). In accordance with package inserts, kaolin tube results tend to be about 5% higher than celite tube results, while cuvette results are about 10% lower than celite tube ACT values. Paired sample t-test analyses incorporating these expected differences showed statistical identity.

Additionally, heparin dose response analyses were conducted on all 12 Signature analyzers to ensure dose response linearity, and incremental unfractionated heparin concentrations were added to aliquots of citrated blood from our volunteers. After recalcification, these samples were tested using ACT+ cuvettes. Regression analyses also were performed to identify linear dose responses. These analyses were repeated six months later using incremental heparin concentrations in aliquots of fresh whole blood, again from normal volunteers. These samples did not require recalcification before testing. Both analyses were conducted following the manufacturer's recommended protocol.

Heparin dose response curves revealed good linearity. For the recalcified, citrated blood samples, correlation coefficients ranged from 0.921 to 0.998 (average r = 0.979), where perfect linearity would be indicated by a correlation coefficient of 1.0. The linearity of the heparin dose response also was observed when using fresh whole blood with correlation coefficients of 0.977 to 0.997 observed across the 12 instruments. Combined data from all 12 instruments yielded a correlation coefficient of 0.988.

Clinical comparison of the two ACT methods was conducted in the cardiovascular area where open-heart surgery is performed. Prior to implementing this study, it was determined that five perfusionists would gather split sample data from four different patients. Later the clinical data collection was expanded from 20 patients to 40. Data collected from the first 20 patients were used to estimate the appropriate target time for use with the Signature system. Based on a Hemochron 801 target of 600 seconds, a tentative Signature target was set at 540 seconds. Data from the subsequent 20 patients were collected to allow perfusionists to perform additional side-by-side analyses to become comfortable with the altered target ranges required when using the ACT+ assay.

The final data set included samples recorded at baseline (N = 33), after heparin bolus (post-hep, N = 39), after initiation of cardiopulmonary bypass (CPB1, N = 39), every 15 minutes on bypass (CPB2, N = 36; CPB3, N 18; CPB4/5, N = 6), and after protamine administration (post-prot, N = 39). Correlation between the test tube and cuvette-based systems was very good (r = 0.89, see Figure 1, page 30), although ACT+ values tended to be lower than the tube results while on bypass (see Figure 2, page 30). Throughout bypass, ACT+ values also showed less variability than those obtained with the test tube system. The lower ACT + target time was found to be clinically equivalent to standard practice with the tube system, with few clinical differences in individually paired results (data not shown).

A secondary evaluation of the effect of hemodilution was performed as well. Hemodilution is a normal side effect of cardiopulmonary bypass when a patient's blood is mixed with the priming solution in the heart lung machine. Mean and standard deviation of ACT results were determined at each hematocrit level recorded during cardiopulmonary bypass for all patients studied. Results showed an elevated clotting time and increased variability in the tube system at low hematocrit levels. This increased variability was not evident in the microsample system.

Addressing clinician concerns

Fortunately, the minor differences observed in the normal ranges between various ACT tests did not hinder clinicians' acceptance of the new system. Developing a new target time for the Signature, on the other hand, was a significant concern. While the ACT+ package insert states the ACT+ clotting time may yield target ranges 10%-l5% shorter than that of the older tube system, personnel from our cardiovascular area were uncomfortable with the differences observed in the initial comparison. Data collected from the first 20 patients allowed determination of a revised target time of 540 seconds to yield equivalent clinical results for a kaolin-activated ACT of 600 seconds. Data compiled from the next 20 patients allowed clinical confirmation of the new target.

The critical issue raised by the new target time revolved around the increased differences between the two ACT systems as test tube clotting times increased beyond 600 seconds, clearly evident in the correlation data (see Figure 1). Hematocrit analysis showed that this increased difference was due, in part, to hemodilution. While a formal analysis of the effects of hypothermia was not conducted, temperature was believed to be a likely confounding effect. Evaluating the clotting time results by clinical decision points revealed that the increased differences had no clinical significance (see Figure 2).

Additional concerns were addressed during a meeting between the Hemochron manufacturer and representatives from our perfusion, anesthesiology, and pathology departments. Issues addressed at this meeting ranged from fundamental questions (eg, "Why do we monitor?" "What is an ACT?") to more specific areas concerning reagent differences and clinical decision criteria.

Data examining the lack of correlation between ACT and heparin levels as well as the differing effects of various factors on different ACTs were presented at this meeting. Study participants explained that each ACT test system yields different values due to a combination of reagent and methodological effects, which have been well documented over the years. [1] Also discussed was that most systems have some degree of sensitivity to hypothermia and hemodilution. The Hemochron Jr. ACT + requires a sample [greater than]20 times smaller than that required for a celite or kaolin ACT. Previous studies indicate the effects of hemodilution and hypothermia are minimized when the microsample ACT + is used. (This was confirmed at our facility).

Our perfusionists were instrumental in communicating to the laboratory their concerns and ideas on the best way to implement this new system. With their assistance, clinicians in each area of the hospital affected by this new equipment were educated as to the benefits of switching over to the Signature, particularly the elimination of many of the pre-analytical errors associated with our old system due to poor operator technique. Perfusionists especially appreciated the option to keep a printer attached to the Signature to allow review of earlier results while samples are being tested.

Embracing change

Our world is constantly telling us to embrace change. The reality of change is that it is the only constant in today's world, but no one likes it very much. Whenever an established way of performing a procedure is altered, therefore, resistance from participants should be anticipated. This is where proper documentation, effective communication, flexibility, and patience come into play.

This experience has shown us that while embracing change may not be easy, in the long run it's often the best route to take. As we approach almost a year's experience with our new instrumentation, we all agree that switching over to the Hemochron Jr. Signature has been a wise move, offering numerous advantages to operators, lab staff, and patients. Following the performance of numerous comparisons, operators became comfortable with the new procedures and appreciated its added features. Laboratorians' ability to provide a controlled system of data management has been an invaluable asset to our facility, and certainly the decreased sample size required to perform this testing has been a big bonus for our patients.

Mitch West is President of Mid-South Life Support Perfusion Services in Memphis, TN. At Baptist Memorial Hospital East, also in Memphis, Barbara Ebey. Deborah Wobb, and Mark Woods are perfusionists; James J. Holtwick is Hematology Technical Specialist; Lynda S. Meyer is Administrative Director of Clinical Laboratories; and Karen S. Clark is Point of Care Coordinator.


(1.) Hill JD, Dontigny L, de Leval M, Mielke CH Jr. A simple method of heparin management during prolonged extracorporeal circulation. Ann Thorac Surg. 1974;17:129--134.

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[Graph omitted]

The importance of ACT

The ACT, while a simple blood coagulation test, is one of the most critical POCT assays performed in the hospital. Its ability to monitor heparin anticoagulation rapidly and accurately during cardiac surgery and interventional cardiology has been paramount to the success of these interventional procedures over the past 25 years.

First described by Hattersley [1] nearly three decades ago, the ACT is a measure of the time required for a fresh whole blood specimen to clot once exposed to a blood coagulation activator. Upon this contact activation, a series of rapid and dramatic enzymatic events takes place, ultimately resulting in the generation of a fibrin clot. These events traditionally are referred to as the blood coagulation cascade. Among the enzymes involved are thrombin and similar serine proteases, all of which can be inhibited by the interaction of antithrombin III and heparin.

Proper heparin anticoagulation is critical during interventional cardiology and cardiac surgery, as these procedures are inclined to induce unwanted clotting, which can be catastrophic to the patient. [2] The ACT assay also is commonly used in critical care units to determine the appropriate time to remove a femoral access sheath.

As ACT tests have evolved, it has become increasingly evident that each automated system can, and frequently does, yield a different ACT clotting time for the same level of anticoagulation. [3] The point of care ACT test, similar to its laboratory counterpart, the Activated Partial Thromboplastin Time (APTT) test, represents a standardization of blood coagulation contact activation. The ACT is directly reflective of the amount of heparin required to inhibit the enzymatic cascade to prespecified levels.


(1.) Hattersley PG. Activated coagulation time of whole blood. JAMA. 1966;196:150-154.

(2.) Edmunds LH Jr, Addonizo VP Jr. Extracorporeal circulation. In: Colman RD, Hirst J, Marder VJ, Salzman EW, eds. Hemostasis and Thrombosis: Basic Principles and Clinical Practice. 2nd ed. Philadelphia, Pa.: J.B. Lippincott Co.; 1987: 901-912.

(3.) Ferguson JJ. All ACTs are not created equal. Texas Heart inst J. 1992;19:1-3.
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Article Details
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Author:West, Mitch; Ebey, Barbara; Wobb, Deborah; Woods, Mark; Holtwick, James J.; Meyer, Lynda S.; Clark,
Publication:Medical Laboratory Observer
Geographic Code:1USA
Date:Jun 1, 2001
Previous Article:Management Q&A.
Next Article:Multitude of professional organizations offers choices and benefits for laboratorians.

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