Millennium Technology for Critical Care

Transcription

1 C E U P D A T E P O I N T O F C A R E I I I Richard F. Louie Zuping Tang, MD David G. Shelby, MT Gerald J. Kost, MD, PhD Point-of-Care Testing: Millennium Technology for Critical Care ABSTRACT Point-of-care testing (POCT) is an important diagnostic tool used in various locations in the hospital, especially in critical care settings such as the intensive care unit (ICU), the operating room (OR), and the emergency department (ED). This is the third article in a 4-part continuing education series on point-of-care testing. After reading this article, the reader will be able to define POCT, identify its advantages and disadvantages, explain its benefits in critical care settings, understand key features in current point-of-care instruments, identify when a pointof-care test may be inaccurate, and recognize important quality management features of point-of-care instruments. From Point-of-Care Testing Center for Teaching and Research (POCT CTR), School of Medicine, University of California, Davis. Address correspondence to: Mr Richard F. Louie, Medical Pathology, 3453 Tupper Hall, School of Medicine, University of California, Davis, Davis, CA rflouie@ucdavis.edu Laboratory test results are often pivotal to critical care decisions. 1 Testing provides physicians with valuable knowledge about the criticality of the patient so that appropriate therapeutic interventions can be made quickly. There has been growing interest in decentralized laboratory testing, especially point-of-care testing (POCT) in critical care settings (eg, ICU, OR, ED) where rapid therapeutic turnaround time is needed. 2,3 However, some types of POCT are controversial because of concern about the accuracy and performance of instruments when used with critically ill patients (ie, glucose meter testing). 4,5 Point-of-Care Testing Defined Point-of-care testing is defined as testing at or near the site of patient care whenever the medical care is needed. 6 The purpose of POCT is to provide immediate information to physicians about the patient s condition, so that this information can be integrated into appropriate treatment decisions that improve patient outcomes, that is, reduce patients criticality, morbidity, and mortality. Point-of-care testing can be performed in different environments, such as in the hospital, at home, or at other locations. Types of Point-of-Care Instruments Point-of-care instruments vary widely and can be categorized as transportable, portable, or handheld, based on the format. Some are capable of testing specific analytes, while others are capable of performing an array of tests (eg, electrolytes and blood gases). Tables 1 and 2 list test parameters and specifications of the latest whole-blood analyzer/biosensor platforms and handheld/portable glucose meters, respectively. Point-of-care instruments differ by their method of testing. For example, whole-blood glucose meters are categorized as electrochemical biosensor, reflectance photometry, or absorbance photometry. These instruments are further differentiated by the type of chemistry used to measure the glucose: either glucose oxidase or glucose dehydrogenase enzymes. Advantages of Point-of-Care Testing Table 3 summarizes some of the advantages of POCT. The first advantage of POCT is the short therapeutic turnaround time of patient sample testing. 7,8 The average turnaround time expected by critical care physicians is 5 to 15 minutes. 1 Stat tests are frequently requested in critical care units. Depending on the instrument used, the type of test, and the number of tests performed, the analysis time of a whole-blood sample can vary from 15 seconds to 2 minutes 20 seconds (Tables 1 and 2). Delays could yield results that do not reflect the patient s current condition. One benefit of rapid therapeutic turnaround time is that it allows physicians to begin implementing appropriate treatment early, especially for those patients in critical care units where delays can adversely affect patient outcomes. A second advantage to POCT is potential reduction of preanalytic and postanalytic errors. Traditional methods of laboratory testing involve multiple preparatory steps. With increased process steps, there is an increased possibility of introducing preanalytic 4 0 2

2 Table 1. Characteristics of Whole-Blood Analyzers Sample Analysis Time Instrument Manufacturer Type Volume (ml) (seconds) Test Analytes (measured) i-stat* Abbott Diagnostics, Handheld 65 or po 2, ph, Na +, K +, Ca ++, Abbott Park, IL Cl -, Hct, urea nitrogen, glucose, lactate, creatinine AVL OMNI AVL Scientific, Transportable po 2, ph, Na +, K +, Roswell, GA Ca ++, Cl -, Hct, Hb, urea nitrogen, glucose, lactate, creatinine AVL OPTI AVL Scientific Portable 125 <120 po 2, ph, Na +, K +, Ca ++, Cl -, Hb Rapid Lab 800 Bayer Diagnostics, Transportable po 2, ph, Na +, K +, Ca ++, Cl -, series Norwood, MA glucose, lactate IRMA SL Agilent Technologies, Portable po 2, ph, Na +, K +, Ca ++, Hct (series 2000) St Paul, MN HemoCue HemoCue, Portable Hb B-Hemoglobin Mission Viejo, CA Gem Premier Instrumentation Portable 135 <120 po 2, ph, Na +, K +, Ca ++, Hct, 3000, 3001 Laboratory glucose, lactate Lexington, MA Stat profile phox Nova Biomedical, Transportable po 2, ph, SO 2 %, Hct, Hb Waltham, MA Stat Profile Nova Biomedical Transportable po 2, ph, SO 2 %, Na +, K +, Ca ++, M/M7 Mg ++, Cl -, Hct, urea nitrogen, glucose, lactate, creatinine Nova series Nova Biomedical Transportable Na +, K +, Cl -, Hct, TCO 2, Hct, urea (16) nitrogen, glucose, creatinine ABL 700 Radiometer, Transportable po 2, ph, Na +, K +, Ca ++, Cl -, series Westlake, OH glucose, lactate ABL 70 Radiometer Portable <180 <60 po 2, ph, Na +, K +, Ca ++, Hct Series YSI 2300 Yellow Springs Transportable Glucose, lactate Stat Plus Instrument, Yellow Springs, OH Portable indicates easily carried, usually with a built-in handle; transportable, equipment usually carried on a cart; po 2, blood oxygen tension; pco 2, blood carbon dioxide tension; SO 2 %, oxygen saturation; TCO 2, total carbon dioxide in blood; Na +, sodium; K +, potassium; Ca ++, ionized calcium; Mg ++, magnesium; Cl -, chloride; Hct, hematocrit; Hb, hemoglobin. * i-stat test cluster capability is cartridge dependent. Co-oximetry available as a modular add-on. AVL OMNI test cluster is instrument-model dependent includes optimal modular prothrombin time (PT), activated partial thromboplastin time (aptt), and activated clotting time (ACT) tests. errors. 1 Some common preanalytic and postanalytic errors associated with traditional laboratory testing are listed in Table 4. Delays in specimen processing and testing may allow samples to degrade. The subsequent testing may yield results that do not represent the actual status of the patient. This is especially true when blood gases, ph, and glucose are tested. Performing tests immediately at the bedside minimizes both preanalytic and postanalytic errors, because bedside testing eliminates time delays due to specimen transportation and multiple persons handling a patient specimen. Postanalytic errors can be minimized because results from bedside testing are immediately available to the clinical team and can be printed out or stored in memory by the instrument. Furthermore, the results are recorded directly onto the patient s chart. Point-of-care testing is convenient for clinicians, because it can be performed quickly, and results are readily available. As point-of-care test menus expand, we will find that based on real-time clinical need, POCT drives diagnostic testing. Current point-of-care instruments are user friendly, which allows nontechnically oriented or nonlaboratory professionals to operate instruments. Many pointof-care devices are self-contained with on-screen instructions, which promote ease of use. Several point-of-care devices are low maintenance because they are self-contained, use disposable test cartridges, and the test cartridges are readily replaced. Finally, POCT is advantageous because of the small sample volume required to perform a test. Patients potentially lose 25 to 125 ml of blood each day, or up to 944 ml of blood per hospital stay through phlebotomy for traditional centralized laboratory testing Oftentimes, in the OR, ICU, and Section 4 Scientific Communications JULY 2000 VOLUME 31, NUMBER 7 LABORATORY MEDICINE 4 0 3

3 Table 2. Characteristics of Glucose Monitoring Devices Instrument* Manufacturer Sample Volume (ml) Analysis Time (seconds) HemoCue B-Glucose HemoCue, Mission Viejo, CA 5 < 90, if [Glu] < 140 mg/dl < 240, if [Glu] < 400 mg/dl Precision PCx Abbott Diagnostics, Bedford, MA Precision G Abbott Diagnostics Precision QID Abbott Diagnostics SureStepPro LifeScan, Milpitas, CA One Touch Hospital LifeScan FastTake LifeScan Glucometer Elite Bayer, Elkhart, IN 5 30 Accu-Chek Advantage H Roche Diagnostics, Indianapolis, IN Accu-Chek Comfort Curve Roche Diagnostics 4 45 * Systems use handheld meters and glucose test strips, except the HemoCue B-Glucose, which is a portable analyzer that uses a cuvette and photometric absorbance to measure glucose. The SureStepPro and One Touch Hospital test strips use photometric reflectance. Test strips for the other systems incorporate electrochemical (amperometric) biosensors for glucose measurement. GO indicates glucose oxidase; GD, glucose dehydrogenase. Test limitations are those provided by the manufacturers and list the recommended test conditions to yield the optimal results. ED, there is demand for frequent serial whole-blood testing. Serial testing of patients with respiratory failure or distress, acid-base imbalance, or surgery provides useful trend monitoring, which is helpful when determining whether current therapy is effective. Serial whole-blood testing may be as frequent as every 15 to 30 minutes during open heart surgery. Such frequent laboratory testing results in extensive blood loss, which could lead to unwarranted transfusions as well to unforeseen health complications (eg, transfusionacquired illness, infections, and iatrogenic anemia). In the treatment of critically ill patients, minimizing blood loss is of utmost importance. 8,11,12 Point-of-care instruments are capable of providing a cluster of tests with minimal blood loss (as low as 40 µl), depending on the instrument used and the test performed. Current point-of-care instruments can provide up to 14 simultaneously measured test parameters (Table 2). This strategy conserves blood and minimizes health complications and unnecessary transfusions. 12 Disadvantages of Point-of-Care Testing Table 3 summarizes some of the disadvantages of POCT. A concern that arises with POCT is the accuracy and performance of the instrument when used in critical care settings. One important question is whether interfering substances in the specimen can affect instrument performance. This concern is especially true in critical care, where changes in blood gases, ph, glucose, and medication levels can pose a potential problem to whole-blood biosensors. Although studies 13,14 have documented the accuracy of point-of-care test results compared with that of laboratory test results, the accuracy of smallerformat devices remains controversial (eg, bedside glucose testing with handheld devices). Recent studies 4,5,15,16 have documented the potential effects of high or low blood oxygen tension, hematocrit, and ph levels, which could cause handheld glucose meters to report higher or lower glucose values. Because the responsibility of POCT in critical care is usually assigned to nonlaboratory professionals, 2,17 another concern with POCT is whether measurements by nonlaboratory professionals (eg, nurses, physicians) are accurate compared to measurements by laboratory professionals. Studies have reported that measurements obtained by nonlaboratory professionals with the proper training can be as accurate as those obtained by laboratory professionals. 14,18 Measurements generally are accurate if operators have been properly trained in quality assurance and instruments are properly maintained. There is additional concern that nonlaboratory professionals may not have adequate understanding or appreciation of the significance of quality control and quality assurance for testing devices. 2,17 Nonlaboratory professionals may not take adequate responsibility for quality management and performance enhancement, thereby potentially affecting patient results. Therefore, it is important that the hospital team (ie, physicians, nurses, medical technologists, 4 0 4

4 Test Limitations Linearity (mg/dl) Chemistry Hct (%) po 2 (mmhg) GO None None None GO None GO None GO None GO 25-60, adults None 25-65, neonates GO 25-60, adults < 45, [Glu] > 150 mg/dl 25-76, neonates 25-76, [Glu] 150mg/dL > 60, [Glu] < 150 mg/dl GO None GO None > 55, [Glu] < 300 mg/dl GD 20-65, [Glu] < 200 mg/dl None 20-55, [Glu] > 200 mg/dl GD 20-65, [Glu] < 200 mg/dl None 20-55, [Glu] > 200 mg/dl The equation to convert to SI units is: mmol/l = mg/dl Handheld device for measurement of glucose and ketones planned. Hematocrit limits apply to neonate samples only. respiratory therapists, and pathologists) know the proper operating procedures and limitations of their point-of-care testing instruments, whether they are testing for glucose, electrolytes, blood gases, cardiac markers, coagulation indices, or other analytes. Hospital staff working with these instruments should be familiar with and responsible for quality management of their instruments, to ensure the reliability of the patient test results. Administrative staff (ie, nurse managers, coordinators of point-of-care testing programs, and managers of quality assurance programs) should keep up-to-date with proficiency testing of operators of point-of-care instruments at their facility as well as be able to train new operators and assess operators competence. Quality management deals with measures taken by operators of point-of-care instruments to ensure that instruments are accurate and performing optimally. Compromising the accuracy and precision for expeditious testing is not recommended. Each medical institution should have its own quality assurance committee that is responsible for the competence of operators and for decisions about expected performance standards of the entire testing cycle. Additionally, operators must take necessary measures to comply with regulations. To regulate the performance of laboratory testing (including point-of-care testing), the federal government requires that each medical institution meet the standards established by the Clinical Laboratory Table 3. Advantages and Disadvantages of Point-of-Care Testing Advantages Reduced therapeutic turnaround time of diagnostic testing Rapid data availability Reduced preanalytic and postanalytic testing errors Self-contained and user-friendly instruments Small sample volume for a large test menu Shorter patient length of stay Convenience for clinicians Ability to test many types of samples (ie, capillary, saliva, urine) Disadvantages Concerns about inaccuracy, imprecision, and performance (ie, potential interfering substances) Bedside laboratory tests performed by poorly trained nonlaboratorians Quality management/assurance issues and responsibilities not defined Cost of point-of-care testing compared with traditional laboratory testing Quality of testing is operator-dependent Difficulty in integrating test results with hospital information system (HIS) or laboratory information system (LIS) lack of connectivity Narrower measuring range for some analytes Improvement Amendments of 1988 (CLIA 88). Compliance with the Joint Commission on Accreditation of Healthcare Organizations (JCAHO, Oakbrook Terrace, IL) or College of American Pathologists (CAP, Northfield, IL) regulations is voluntary. All medical institutions must comply with state laws. These laboratory testing regulations help to ensure the high-quality performance of the Section 4 Scientific Communications JULY 2000 VOLUME 31, NUMBER 7 LABORATORY MEDICINE 4 0 5

5 Table 4. Preanalytic and Postanalytic Errors Preanalytic errors Mishandling and/or mislabeling of patient specimen Contamination of specimen Degradation of specimen due to delays in specimen processing/testing and/or arrival at central laboratory Postanalytic errors Misreporting patient test results Recording wrong patient test results Lost data Delayed reporting of critical results Table 5. Cost Factors in Point-of-Care Testing Supplies (eg, reagents, disposable cartridges, test strips) and equipment Training and retraining of instrument operators Maintenance of instruments, including replacing defective instruments Additional labor on the part of nonlaboratorians (eg, nurses) to run patient tests New software that enables patient results to be entered into hospital/laboratory information systems (HIS/LIS) Troubleshooting instruments Consultation services for instrumentation problems Performing comparison studies of new instruments and methodologies with existing instruments Accreditation and proficiency testing fees Duplication, repeated tests, verification, and validation instruments as well the proper practice of diagnostic testing by the operators. Quality control compliance is one of the many quality management monitors used routinely with POCT devices. The Figure illustrates documentation of QC compliance rates of critical-care operators and all other operators of point-ofcare devices at the University of California, Davis, Health System (UCDHS). As part of the quality assurance and performance-improvement program at UCDHS, an progress report is issued monthly to nurse supervisors of each department by the pathology POCT manager. The report provides an assessment of the overall QC compliance rate of that department and compares the department s performance to the rest of the hospital. If the department compliance rate falls below the rest of the hospital, a message in the emphasizes the necessity for improvement to meet JCAHO and CLIA guidelines. Performance has improved steadily with the electronic broadcast approach. Finally, there is growing debate about the cost-effectiveness of POCT. It has been argued that the cost for POCT compared to centralized laboratory testing may be less, more, or may show no difference. 19,20,21 Table 5 lists some factors that contribute to the costs of POCT. While it appears that POCT may be more expensive than laboratory testing, some argue that the benefits of POCT the small sample volume 12 and short therapeutic turnaround time 7 could shorten the length of patient stay or offset the costs of POCT or both. POCT in the operating room is cost-effective for hemostasis evaluation and transfusion management. 22 In some cases, such as rapid parathyroid hormone (PTH) testing for parathyroid surgery, speed alone is crucial in saving operating room time and reducing the length of hospitalization. 23 Recent studies demonstrated that point-of-care testing can reduce the length of hospital stay 24 and time in the emergency department, 25 but further study is needed to validate these results. Technology of Whole-Blood Biosensors Whole-blood analyzers currently use both electrochemical sensors and other methods (ie, optical sensors) for specimen analysis. Electrochemical sensors are categorized as either potentiometric or amperometric and include the ion-selective electrode (ISE) and substrate-specific electrode (SSE). The electrical conductance (impedance) sensor (ECS) is used to measure hematocrit indirectly. Optical sensor technology includes spectrophotometry, absorbance photometry, and reflectance photometry. Table 6 lists analytes commonly tested with these methods. Ion-selective electrodes operate by determining the electrical potential (relative to the reference electrode potential) established by ions across selectively permeable membranes. The difference in potential across the membrane is logarithmically proportional to the specific ion concentration (activity) in the blood. The operation of a substrate-specific electrode is illustrated when testing for glucose using the YSI 2300 Stat Glucose/Lactate Analyzer. Glucose is oxidized with the catalysis of glucose oxidase to form gluconic acid and hydrogen peroxide. Hydrogen peroxide subsequently becomes oxidized, and a platinum electrode measures the current that forms. The current formed is proportional to the glucose (substrate) concentration (molality). The electrical conductance sensor operates by measuring the impedance of the current flow in the sample. The impedance of the current is measured by applying an alternating voltage across 2 or more electrodes in contact with the blood sample. Features of Current Whole-Blood Point-of-Care Analyzers and Glucose Meters Notable features of point-of-care instruments include expanded test options, shortened analysis time, reduced sample test volume, and automated quality management. Current instruments are able to measure up to 14 different tests per sample of blood, compared to the 8 to 11 tests in previous generations. Many of the current instruments require a small blood volume to perform a test as little as 2.5 µl for a single measurement on a handheld glucose meter, or as little as 40 µl for 1 or 2 measurements, such as glucose and lactate, on a whole-blood analyzer. The analysis time can be as rapid as 15 seconds for a single measurement, or 45 seconds for a multipleparameter test; hence, shortening the therapeutic turnaround time. The latest whole-blood analyzers have the capability of providing selective testing; that is, the operator may select the tests to be performed, thereby eliminating unnecessary tests, which can generate financial losses and waste patient blood

6 Advanced quality management features also appear on the latest instruments. Most wholeblood analyzers are equipped with automatic internal 1- and 2-point calibrations at various time intervals ranging from every 15 minutes to every 2 hours. Some instruments have automatic or electronic QC (EQC). Automatic QC ensures that QC testing is performed routinely at regular intervals. The purpose of EQC is to test the electronics; that is, the internal and analyte circuits of the instrument. However, EQC doesn t validate the performance of the test cartridges or of the operator. EQC can help generate cost savings because it is convenient, can be completed quickly, is reagentless, requires only a reusable EQC card, and is a beneficial feature that assesses the electronic measurement cycle of the instrument. It is important to realize that manufacturers of instruments with the EQC feature do not recommend substituting EQC for aqueous QC. Aqueous and electronic QC should both be performed. A QC lockout feature, when enabled, does not allow the operator to perform any patient testing unless quality control testing has been performed and has satisfied the vendor-specified QC ranges. Other lockout and security features include a password option, which must be entered by a certified operator before the instrument can be used for patient testing, Compliance Rate (%) Quality control (QC) compliance rates. QC compliance rates are shown as a function of time for critical care settings and all hospital areas at the University of California, Davis, Health System from January 1998 through September The line for all critical care units is based on 14 different critical care settings, including intensive care units, the operating room, and the emergency department. The line for all hospital areas is based on 57 settings. The graph shows progressive performance enhancement after instituting electronic mail broadcasting. thus ensuring proper usage of the instrument. Some instruments require that proper patient identification be entered before testing can proceed. This action ensures proper documentation of test results. Future of Point-of-Care Instruments and Testing An important issue to address now about POCT is the accuracy, performance, and reliability of these Table 6. Methods for Analyte Measurements Method Ion-Selective Substrate-Specific Electrical Conductance Analyte-Specific Optical Analyte Electrode (ISE) Electrode (SSE) Sensor (ECS) Sensor (ASOS) Ca ++ Yes No No No Mg ++ Yes No No No K + Yes No No No Cl Yes No No No Na ++ Yes No No No ph Yes No No Yes PCO 2 CO 2 -sensitive buffer, No No Yes with ph electrode po 2 No Amperometric No Yes Glucose No Yes No No Lactate No Yes No No Urea Nitrogen No Yes No No Creatinine No Yes No No Dec 97 Hematocrit No No Yes No Hemoglobin No No No Multiwavelength reflectance Total CO 2 Acid displacement, No No No CO 2 -sensitive buffer, with ph electrode O 2 saturation No No No Optical reflectance Jan 98 Feb 98 Mar 98 Apr 98 May 98 Jun 98 Jul 98 Aug 98 Sep 98 Oct 98 Nov 98 Dec 98 Month/Year Jan 99 Feb 99 Mar 99 All critical care units All hospital areas Apr 99 May 99 Jun 99 Jul 99 Aug 99 Sep 99 Section 4 Scientific Communications JULY 2000 VOLUME 31, NUMBER 7 LABORATORY MEDICINE 4 0 7

7 Test Your Knowledge! Look for the CE Update exam on Point-of-Care (004) in the August issue of Laboratory Medicine. Participants will earn 4 CMLE credit hours. instruments for patient testing in the critical care setting. More study is needed to examine the limitations of these instruments and to resolve any potential error sources (eg, interfering substances) that may affect instrument performance. However, in regard to short-term advances with pointof-care technology, we will see continued expansion of test menus, shorter analysis time, and reduced sample volume. For example, several devices are now available for hemostasis testing at the point of care, 26 for other point-of-care analytes not listed in Table 1 (eg, ß-hydroxybutyrate, therapeutic drugs, and drugs of abuse), and for cardiac-injury markers (eg, troponin I, CK-MB, and myoglobin). Several additional point-of-care analytes are under development. Additionally, POCT will be connected in the near future. Test results will be downloaded and recorded readily into the hospital and laboratory information system (HIS/LIS). The first meeting of the Connectivity Industry Consortium (CIC) on POCT was held October 20, 1999, in Redwood City, CA, to facilitate this process. The CIC members set a goal of writing and publishing connectivity standards for near-patient and point-of-care instruments by the end of the year Point-of-care testing undoubtedly will take a more active role in critical care settings. It will be used more for on-site diagnostic testing and trend monitoring of patient conditions, due in part to the increasing percentage of critically ill patients in hospitals, the need for shorter therapeutic turnaround time, and bidirectional connectivity of transportable, portable, and handheld devices. While POCT may not necessarily replace centralized laboratory testing, it is becoming an important modality for improving patient care and outcomes.l Acknowledgments The authors would like to acknowledge Joan Bullock for her contribution of information and insights into the Quality Assurance Program at the University of California, Davis, Health System, and thank the vendors for providing information on their products. References 1. Harvey MA. Point-of-care laboratory testing in critical care. Am J Crit Care. 1999;8: Lamb LS, Parrish RS, Goran SF, et al. Current nursing practice of point-of-care laboratory diagnostic testing in critical care units. Am J Crit Care. 1995;4: Kost GJ, Ehrmeyer SS, Chernow B, et al. The laboratory-clinical interface: point-of-care testing. Chest. 1999;115: Kost GJ, Vu H, Lee JH, et al. Multicenter study of oxygeninsensitive handheld glucose point-of-care testing in critical care/hospital/ambulatory patients in the United States and Canada. Crit Care Med. 1998; 26: Louie RF, Tang Z, Sutton DV, et al. Point-of-care testing: effects of critical care variables, influence of reference instruments, and a modular glucose meter design. Arch Pathol Lab Med. 2000;124: Kost GJ. Guidelines for point-of-care testing: improving patient outcomes. Am J Clin Pathol. 1995;104(suppl 1):S111- S Kilgore ML, Steindel SJ, Smith JA. Evaluating stat testing options in an academic health center: turnaround time and staff satisfaction. Clin Chem. 1998;44: Chernow B, Salem M, Sacey J. Blood conservation: a critical care imperative. Crit Care Med. 1991;19: Zimmerman JE, Seveff MG, Sun X, et al. Evaluating laboratory usage in the intensive care unit: patient and institutional characteristics that influence frequency of blood sampling. Crit Care Med. 1997;25: Peruzzi WT, Parker MA, Lichtenthal PR, et al. A clinical evaluation of a blood conservation device in medical intensive care unit patients. Crit Care Med. 1993;21: Chernow B. Blood conservation in critical care: the evidence accumulates. Crit Care Med. 1993;21: Salem M, Chernow B, Burke, et al. Bedside diagnostic testing: its accuracy, rapidity, and utility in blood conservation. JAMA. 1991;266: Wahr JA, Lau W, Tremper KK, et al. Accuracy and precision of a new, portable, handheld blood gas analyzer, the IRMA. J Clin Monit. 1996;12: Zaloga GP, Roberts PR, Black K, et al. Hand-held blood gas analyzer is accurate in the critical care setting. Crit Care Med. 1996;24: Tang Z, Lee JH, Louie RF, et al. Effects of different hematocrits on glucose measurements with handheld meters for point-of-care testing. Arch Pathol Lab Med. In press. 16. Tang Z, Du X, Louie RF, et al. Effects of ph on glucose measurements with handheld glucose meters and portable glucose analyzer for point-of-care testing. Arch Pathol Lab Med. 2000;124: Lamb LS. Responsibilities in point-of-care testing: an institutional perspective. Arch Pathol Lab Med. 1995;119: Zaloga GP, Dudas L, Roberts P, et al. Near-patient blood gas and electrolyte analyses are accurate when performed by non-laboratory-trained individuals. J Clin Monit. 1993;9: Kilgore ML, Steindel SJ, Smith JA. Cost analysis for decision support: the case of comparing centralized versus distributed methods for blood gas testing. Journal of Healthcare Management. 1999;44: Halpern MT, Palmer CS, Simpson KN, et al. The economic and clinical efficiency of point-of-care testing for critically ill patients: a decision-analysis model. Am J Medical Qual. 1998;13: De Cresce RP, Phillips DL, Howanitz PJ. Financial justification of alternate site testing. Arch Pathol Lab Med. 1995;119: Depotis GJ, Santoro SA, Spitznagel E, et al. Prospective evaluation and clinical utility of on-site monitoring of coagulation in patients undergoing cardiac operation. J Thorac Cardiovasc Surg. 1994;107: Scott MG. Is faster better? An outcomes approach to POCT implementation decisions. In: Managing Your POCT Program for Success. Washington, DC: American Association for Clinical Chemistry. Audio Conference, January 20, Collinson PO. The need for a point of care testing: an evidence-based appraisal. Scand J Clin Lab Invest. 1999;59(suppl 230): Murray RP, Leroux M, Sabga E, et al. Effects of point of care testing on length of stay in an adult emergency department. J Emerg Med. 1999;17: Kost GJ. Point-of-care testing. In: Meyer RA, ed. Encyclopedia of Analytical Chemistry: Instruments and Applications. New York, NY: John Wiley and Sons; 2000, chap 540. In press