Transducers-Point of Control Instrumentation

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A report on

POINT OF CARE INSTRUMENTATION

November 14, 2011

INSTR_C381_TRANSD_&_MEASUREMENT_SYS

By

AnkitAsati (2008B3A8600G)

INTRODUCTION

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To understand the point of care instrumentation, first we should understand whatPoint of Care Testing is. This is explained below:

What is POC Testing?

Point-of-care testing (POCT) is defined as medical testing at or near the site ofpatient care. The driving notion behind POCT is to conduct the test conveniently andimmediately for the patient. POCT increases the likelihood that the patient,physician, and care team will receive the results quicker, which allows forimmediate clinical management decisions to be made.

Purpose

The purpose of POCT is to provide immediate information to physicians about the

patients condition, so that this information can be integrated into appropriatetreatment decisions that improve patient outcomes, that is, reduce patientscriticality, morbidity, and mortality. Point-of-care testing can be performed indifferent environments, such as in the hospital, at some, or at other locations. Imajor purposes can be briefly summarized as:

For Monitoring chronic disease (or acute disease in ICUs)

For Diagnosis, risk stratification

For Screening

Why consider POC Testing?

A major mission of clinical laboratories is to provide high-quality, efficient, timelylaboratory testing to the healthcare community at a reasonable cost. With theadditional pressure that economics has created in health care today (managed care,Medicare, capitation), it can become a real challenge to meet these three criteria toaccomplish our mission. POCT can be an opportunity to achieve this, by providing astimulus for managers to rethink how they provide laboratory services. It canmotivate us to look at things in a different light.

Technological Specifications

Two broad types of technology support point of care testing:

1. Small bench top analyzers

The bench top systems are smaller versions of laboratory analyzers in whichvulnerable operator dependent steps have been automatedfor example,automatic flushing of sample after analysis, calibration, and quality control

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2. Hand held, single use devices

Hand held devices have been developed using micro fabrication techniques. Theyare outwardly simple but internally complex devices that do several tasksforexample, separate cells from plasma; add reagents, and read color or other endpoints.

Types of Point of Care Instruments

Point-of-care instruments vary widely and can be categorized as

TransportableIt is equipment usually carried on a cart.

Portable or HandheldIt is equipment that can be easily carried, usually with a built-in handle.

Point-of-care instruments also differ by their method of testing. For example, whole-

blood glucose meters are categorized as

electrochemical biosensor

reflectance photometry

absorbance photometry

These instruments are further differentiated by the type of chemistry used tomeasure the glucose: either glucose oxidase or glucose dehydrogenase enzymes.

One of the most important components of a POC instrument is BIOSENSOR. So

now let us understand what a Biosensor is.

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A biosensoris an analytical device for the detection of an analyte thatcombines a biological component with a physicochemical detectorcomponent.

Biosensor is actually Bioreceptor + Transducer+. A biosensor consists oftwo components: a bioreceptor and a transducer. The bioreceptor is abiomolecule that recognizes the target analyte whereas the transducer convertsthe recognition event into a measurable signal. The uniqueness of a biosensor isthat the two components are integrated into one single sensor .This combinationenables one to measure the target analyte without using reagents. The

simplicity and the speed of measurement are the main advantages of abiosensor.

Another component of biosensor is its Reader device with the associatedelectronics or signalprocessors that are primarily responsible for the display ofthe results in a user-friendly way.

Biosensors are used to analyze various physical, chemical and biologicalprocesses. Heat, light and electricity are the results of various reactions. Those properties are exploited to analyze reactions. There are different types ofbiosensors depending on the type of property used to analyze a reaction.Followings are the different types of biosensors:
http://www.wikispot.info/2010/08/thermometric-biosensors.html


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Some Practical Examples of POCT Instruments

For non-infectious agents as:

Glucometers Blood gas monitors Pregnancy

Cardiac monitors

As Infection markers in:

Acute phase reactants C-reactive protein

For infectious agents in:

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Amperometric biosensors; potential based biosensors Acoustic wave biosensors ; sound based biosensors Hybrid biosensors ; combination

A common example of a commercial biosensor is the blood glucose biosensor,

which uses the enzyme glucose oxidase to break blood glucose down. In doingso it first oxidizes glucose and uses two electrons to reduce the FAD (acomponent of the enzyme) to FADH2. This in turn is oxidized by the electrode(accepting two electrons from the electrode) in a number of steps. The resultingcurrent is a measure of the concentration of glucose. In this case, the electrodeis the transducer and the enzyme is the biologically active component

Applications of Biosensor

Clinical diagnosis and biomedicine

Farm, garden and veterinary analysis Process control: fermentation control and analysis food and drink

production and analysis

Microbiology: bacterial and viral analysis

Pharmaceutical and drug analysis

Industrial effluent control

Pollution control and monitoring o Mining, industrial and toxic gases

Military applications
http://www.wikispot.info/2010/08/amperometric-biosensors.htmlhttp://en.wikipedia.org/wiki/Blood_glucosehttp://en.wikipedia.org/wiki/Glucose_oxidasehttp://www.wikispot.info/2010/08/amperometric-biosensors.htmlhttp://en.wikipedia.org/wiki/Blood_glucosehttp://en.wikipedia.org/wiki/Glucose_oxidase


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Influenza HIV STI Meningococcal

Quality control and Quality Assurance for POC tests

Even with the most sophisticated device, reliable results can be obtained only if thepatient is prepared appropriately and the correct technique is used. As point of caretesting is likely to be done by staff with limited technical background, training andquality control are critical.

Wherever possible, point of care testing equipment should be linked to thelaboratory information system to enable real time monitoring of performance andintegration of results into the patient's electronic record. This approach should meetall the requirements associated with clinical risk management and clinicalgovernance.

This is where the issue ofQuality controland Quality Assurance arises. So letsus understand these terms:

Quality control (QC)

Quality control (QC) is essentially establishing adequate performancecharacteristics (sensitivity, specificity, negative predictive value, positivepredictive value, cross reactivity, etc.) of a given test kit. Quality assurance(QA) is determining the ongoing adequate performance of a test in analysis ofclinical conditions. QC for POC tests is reasonably straightforward, involvingthe comparison of new rapid tests against established methods such as viralculture, bacterial culture, nucleic acid tests and other reference standards instatistically adequate numbers of positive and negative analyte. As such, QCfor POC tests can be performed, robust performance characteristicsestablished, and the tests used.

Advanced quality management features also appear on the latestinstruments. Most whole blood analyzers are equipped with automaticinternal 1- and 2-point calibrations at various time intervals ranging from

every 15 minutes to every 2 hours. Some instruments have automatic orelectronic QC (EQC). Automatic QC ensures that QC testing is performedroutinely at regular intervals.

The purpose of EQC is to test the electronics; that is, the internal and analytecircuits of the instrument. However, EQC doesnt validate the performance ofthe test cartridges or of the operator. EQC can help generate cost savingsbecause it is convenient, can be completed quickly, is reagent-less, requires

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only a reusable EQC card, and is a beneficial feature that assesses theelectronic measurement cycle of the instrument. It is important to realize thatmanufacturers of instruments with the EQC feature do not recommendsubstituting EQC for aqueous QC. Aqueous and electronic QC should both beperformed.

A QC lockout feature, when enabled, does not allow the operator to performany patient testing unless quality control testing has been performed and hassatisfied the vendor-specified QC ranges. Other lockout and security featuresinclude a password option, which must be entered by a certified operatorbefore the instrument can be used for patient testing, thus ensuring properusage of the instrument. Some instruments require that proper patientidentification be entered before testing can proceed. This action ensuresproper documentation of test results.

Quality Assurance (QA)

QA is an ongoing and lifelong assessment of test performance in real peopleat risk of infection. QA of POC tests is more problematic, particularly if suchtests are to be used by patients at their own bedside. QA assessment of suchtesting is further complicated by the use of newer collection methods 15where the potential for error arises from technical issues associated withcollection, POC testing, operator use, operator test interpretation, and theaction taken by infected patients.

For instance, there is enormous significance surrounding diagnoses of HIV orSTI POC testing that can potentially create significant problems. On the otherhand, POC testing using glucometers by patients with diabetes is well-

established, reasonably accurate and, with suitable clinical backup, has hadenormous positive impact upon the lives on diabetics worldwide.

There are some problems in POC testing, such as lack of consistent qualitysystems, problems with comparability of POC test results with those fromroutine diagnostic laboratories, lack of contact with clinicians able toprescribe therapy, and lack of regulation of such testing. Thus laboratorytesting must be part of validating which tests should be appropriatelyperformed at the bedside.

Apart from these, there are certain other measures to assure the reliability of POCTesting are:

PT Compliance

Proficiency test performance is required for all POCTs. These samples are treatedlike ordinary patient samples and rotated among operators. With connectivity, this

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is easily shown by calling up the results, which include operators who performed thetests. Reagent lot numbers can also be shown.

Reagent Handling

Reagent and control lot numbers and their established values can be enteredinto the system. New lots of reagents show up on an alarm screen, alertingthe POC coordinator that a new lot is in use. If the lot has not beenevaluated, action can be immediately taken to remedy this, preventing useof reagents that have not been validated for acceptability.

Bar coding and reagent scanning prevents use of expired reagents by locking themout. This aids in meeting the standard for reagent verification. Results of calibration

verification using linearity material with known values can be graphed to documentthe reportable range of an analyzer.

Point-of-Care Data Management System

Data Management System gives you flexible, web-based control over the entirepoint-of-care testing program, from anywhere in the hospital. It captures patienttest data from the patient meter and securely transfers this data from dockingstation to desktop.

Advantages and Disadvantages of Point-of-CareTesting

Advantages Reduced therapeutic turnaround time of diagnostic testing

Rapid data availability

Reduced pre-analytic and post-analytic testing errors

Self-contained and user-friendly instruments

Small sample volume for a large test menu

Convenience for clinicians

Disadvantages Concerns about inaccuracy, imprecision, and performance (i.e. potential

interfering substances)

Bedside laboratory tests performed by poorly trained non-laboratorians

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

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Future Prospect

An important issue to address now about POCT is the accuracy, performance, andreliability of these instruments for patient testing in the critical care setting. Morestudy is needed to examine the limitations of these instruments and to resolve anypotential error sources (e.g., interfering substances) that may affect instrumentperformance. However, in regard to short-term advances with point of- caretechnology, we will see continued expansion of test menus, shorter analysis time,and reduced sample volume. Additionally, POCT will be connected in the nearfuture. Test results will be downloaded and recorded readily into the hospital andlaboratory information system (HIS/LIS).

Point-of-care testing undoubtedly will take a more active role in critical caresettings. 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 patientsin hospitals, the need for shorter therapeutic turnaround time, and bidirectionalconnectivity of transportable, portable, and handheld devices. While POCT may notnecessarily replace centralized laboratory testing, it is becoming an importantmodality for improving patient care and outcomes

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Transducers-Point of Control Instrumentation

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