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The impact of biosensors on the clinical laboratory.

A splendid marriage of chemistry to the computer chip is about to change laboratory medicine as surely as the personal computer revolutionized our society in both the workplace and the home.

Biosensors, soon to bloom all over the marketplace, merge the sophisticated capabilities of computer technology, electrochemistry, and enzyme chemistry. The result is instrumentation that can perform ultramicroanalysis with unprecedented speed.

Health care workers with wide ranges of expertise will use biosensors to obtain immediate and accurate results in many different settings. By eliminating a number of steps and much labor, the instrumentation may save a lot of money for labs and hospitals.

The best way to grasp the impact of this upcoming technology is through the familiar logistics of clinical laboratory service. This article will follow the path of biosensor use from specimen collection to result reporting. We will stop along the way at many potential sites for new ways to obtain measurements and to evaluate them by comparing them via computer with existing data on the patient.

Physical description. Most biosensors consist of two principal components: a molecular recognition element and a transducer or signal-gathering element. A stylized illustration is presented in Figure 1.

The recognition element, which acts as a sensing device, is the biologic component. It may consist of an enzyme, an antibody, a receptor, or an organelle. The second element, the transducer, may be an electrode, a semiconductor, a fiberoptic device, or a quartz crystal. Information is transmitted as a signal sent from the sensing region through the transducer to a readout device.

To illustrate the utility and advantages of biosensor technology, it will be helpful to consider the demands such instruments must fulfill.

Requirements. The cost of reagents used in a biosensor should not exceed the total cost of tests done without it. The ideal system would include a built-in communication device and a bar code reader for patient identification.

As with other lab instrument systems, the sale of biosensor systems would be analogous to the selling of grass seed by the person who provides the grass seed spreader and sells the seed: The buyer must beware. Reputable vendors sell laboratory reagent packs and lease or rent instruments at a nominal fee. The same will undoubtedly apply to the manufacturers of biosensors.

The biosensor of choice will be a cost-effective, relatively inexpensive analytical instrument that provides rapid results. If experience with computer chips over the past decade is any indication, those results will be extremely reliable.

To be of real utility, the biosensor should be compact, even hand-held. Of greatest importance is that almost anyone with minimal training and supervision should be able to use it in virtually any place a patient encounter might occur.

Meeting major needs. Three elements have guided the evolution of laboratory service for 30 years: quality, including accuracy, precision, specificity, and sensitivity; turnaround time; and costs as contrasted with charges for tests. The same elements will apply to biosensors.

Early clinical data suggest that measurements using biosensor technology will be at least as accurate and precise as those obtained with current instrumentation. Although hemoglobin, hematocrit, PT, PTT, and other hematologic procedures are amenable to measurement, the vast majority of determinations by biosensors will probably take place in clinical chemistry. These are likely to include electrolytes (sodium, potassium, chloride, and carbon dioxide), urea nitrogen (BUN), creatinine, calcium (ionized), magnesium, phosphorus, serum protein, and the enzymes-including lactate dehydrogenase (LD), creatine kinase (CK), and the aminotransferases ALT and AST)-as well as blood gases (pH, P02, PCO2, and 02Sat).

Such studies may be readily grouped on a chip in panels or profiles designed to reflect the status of organs, body systems, or medical problems. Laboratory selectivity and a focus on patient problems and diagnosis will be intrinsic to the new technology.

It is easy to imagine how useful biosensors will be in the neonatal intensive-care unit (NICU), for example, helping to determine blood gases and glucose and calcium measurements of the premature infant. Similarly, it will be extremely helpful to have instantaneous on-site determinations for creatinine, BUN, sodium, potassium, chloride, and C02 levels of patients in the dialysis unit of a hospital or at a hemodialysis center. * Fast TAT. Ten-minute turnaround time for blood gases is frequently necessary in both the neonatal and the adult intensive-care units of the hospital. Pulse oximeters have only partially satisfied this demand. Although satellite labs can provide rapid TAT, having a satellite nearby can incur tremendous expense in duplicated instrumentation and labor. Biosensors should provide quick results at far less cost.

The main obstacle would be the current lack of a technique for collecting anaerobic specimens of arterial blood. To solve this problem, an adapter might be developed that would allow sterile anaerobic blood to be collected from arterial lines, which are in place in many critically ill patients.

Biosensors will generate hard copy as well as a visual display and a graphic reflection of reference values-all in less than two minutes. The operator will simply add a small aliquot of whole blood to the appropriate chip and insert it into the instrument. The ability to perform panels and profiles using ultramicroanalysis could markedly reduce neonatal transfusion requirements.

Reducing blood specimen volumes to the micro level may permit continuous on-line monitoring of critical blood chemistries, including blood gases and especially potassium and ionized calcium. On-line monitoring has the advantage of creating less blood to clean up and reducing the potential for infectious contamination from patient blood. For the biosensor to be of optimal use to laboratory service, it must be at least as precise and standardized as other available technology.

Collecting and analyzing specimens at the bedside or in the clinic will enhance the superior turnaround time of biosensors. Cost will be highly competitive by vastly reducing the quantity of reagents needed and the shortened time and labor ordinarily associated with specimen transport, specimen processing during off-hours, laboratory coverage, and result reporting.

Information processing. In a hypothetical scenario, biosensor instruments with built-in infrared communicators will transmit stored data in batch mode to a converter located centrally in the patient care unit. The converter will convey results to the laboratory information system (LIS) and hospital information system (HIS) by telephone line, microwave, direct contact, or telemetry. Measurements will be integrated with other laboratory data right away and will lead to summary clinical pathology reports later.

A wristband bar code system reader will identify patients absolutely at the bedside. The rapid ultramicroanalysis and efficient result reporting that will be made possible through the combination of infrared communicators and absolute patient identification will have a profound impact on the making of decisions regarding diagnosis and patient management. The ability of biosensors to be used in many different settings will change certain aspects of laboratory service related to patient care. The health care worker at the bedside of a hospital patient, for example, will be able to perform a skin puncture, collect a 30-(micro)l aliquot of whole blood directly into the chip, and insert the chip into a portable biosensor instrument. The result: true ultramicroanalysis with no specimen processing required. A single chip insert may contain four, six, eight, or more discrete and different measurements. This multiplicity in itself will save considerable time and effort over the specimen processing that constitutes a substantial part of today's laboratory workload. Conveying measurement results to the LIS in digital form will make the process even more efficient. New information can be integrated over time with existing laboratory data on each patient. Incorporating a small buffer memory within the biosensor instrument will permit a number of patient results to be stored and downloaded in batch form to the laboratory or hospital information system at the operator's convenience. This process will reduce the number of interfaces or links to the computer system. Otherwise, either a separate link would be needed at each bedside or numerous trips to interfaces at other central locations would be required.

Sites. Biosensor technology will be of special help in emergency situations. In the ambulance, paramedics or EMTs will measure potassium or drug levels, such as digoxin, lidocaine, and procainamide, or blood glucose and blood gases for the comatose patient. In the emergency room, biosensors will assist in triaging the unconscious patient by providing glucose, BUN, creatinine, blood gas, and electrolyte determinations.

When surgery is called for, the patient can then be moved directly to the operating room. The OR itself is another potential site for biosensor measurements, as is the recovery room after surgery. The technology will be useful on code and crash carts and such hospital departments as the medical, surgical, pediatric, and neonatal intensive-care units.

Thanks to biosensors, blood gases, glucose, BUN, creatinine, electrolytes, calcium, and medications, including therapeutic agents, will be monitored frequently and easily, as needed. In the neonatal intensive-care unit, the ability to obtain immediate glucose and calcium levels, including ionized calcium and blood gases, will be particularly helpful in monitoring the premature infant.

Biosensor instruments can be envisioned on all hospital floors. One might see a biosensor unit being recharged in a wall-mounted battery-recharging unit similar to those used for the Welch Allyn ophthalmoscope/otoscope. An installation might be shared by every four-bed unit or in or near each nursing station. Other biosensors might be carried in the hand or pocket along with insert chips containing reagents. . Lab's role. The pathology department and clinical laboratory will be indispensable in providing quality control for instrumentation, reagents, and determinations of biosensors used in the hospital. In New York State, to take one example, the Department of Health has designated the responsibility and accountability for quality control of all measurements and examinations, including those performed outside the laboratory itself, to clinical laboratory directors (permit holders) and their staffs. This is a responsibility that could be challenged but perhaps facilitated with a biosensor instrument.

Biosensor technology will simplify regular checks for instrument stability, reagent systems, and quality control specimens. A calibration step will be built hip. Microwave into each specimen/reagent insert chip. Microwave or infrared transmission of calibration data to the LIS could allow real-time monitoring of entire lots of reagent chips.

Potential sites for biosensor analysis outside the hospital include extended-care facilities, such as nursing homes, domiciliaries, and home health care. There is no reason biosensor analysis cannot be conducted by visiting nurses and other trained personnel. Physicians will be able to monitor levels of glucose, electrolytes, and therapeutic drugs in patients either on or off the scene.

Off-site dialysis centers will use biosensors to measure BUN, creatinine, and electrolyte levels, especially potassium. The national trend toward wellness and fitness may lead to the placement of biosensors in fitness centers.

Perhaps the most common single environment for biosensor use will be physicians' offices and group practices. Blosensor analyses will be performed at patients' initial and return visits to determine their risk factors and diagnostic or therapeutic needs. The time saving will be of tremendous significance in such settings. . Chemical changes. Biosensors capable of determining 25 different analyses could conceivably replace more than 50 per cent of the hospital laboratory's present clinical chemistry measurements-the majority of which, having been ordered Stat, require fast turnaround time. Since chemistry represents approximately 50 per cent of the total hospital laboratory workload, the potential logistical and economic benefits to patients, physicians, laboratory staff, and possibly the hospital overall are enormous.

Pathologists would probably support a reduction in the number of Stats. It will be difficult to beat or even match the reagent cost of 10 cents per test, however, for non-Stat determinations. Any lab handling a large volume of determinations and needs other than Stat will continue to rely on current instrumental systems of analyses, which provide high quality at substantially lower cost. *Manager's role. Laboratory managers should prepare now to assess biosensors closely as they enter the market. We must make sure they become incorporated into the laboratory and allocated and used appropriately.

As in all things, lab managers may have to accommodate the state and Federal governments. Any relevant regulations that may be issued by the CDC, by OSHA, or by HCFA must be heeded. More Federal recommendations will probably come into play. Although the use of gloves in blood specimen collection is not currently mandated by the Centers for Disease Control, for example, such use is strongly recommended when contamination is likely.

Laboratory service and patient care have much to gain from biosensors. Laboratory managers should remain alert for developments and be ready to learn to use and implement this important technology. n
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Article Details
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Author:Henry, John Bernard
Publication:Medical Laboratory Observer
Date:Jul 1, 1990
Previous Article:Finding the diamond in the rough.
Next Article:Automated immunoassay systems: a new frontier.

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