Testing in the lab or at the bedside?
Describe the rise of sample testing in a near patient setting giving examples, and explain some of the pros and cons of this approach.
Medicine is modernising due to clinical research and technological advances creating a growing demand for rapid test results so that clinicians can make accurate decisions and give a diagnosis as quickly as possible, hence the increasing popularity of point of care testing(POCT). In the following essay I will evaluate what exactly a POCT is whilst investigating its advantages and disadvantages against the traditional laboratory testing. From this i will be able to conclude as to why Point of care tests are becoming increasingly used in hospitals.
What is a Point-of-Care test
POCT, also referred to as near patient testing, is an analytical test which is conducted in a setting away from the laboratory, usually at or near the patient's bedside, which provides rapid results and can be performed by either a trained clinician or a non medical personal. POCT's have seen a transformation in clinical equipment from large extensive laboratory analyzers to miniature, portable, easy to use analysers () . POCT are primarily used in critical care units such as the accident and emergency department and the intensive care unit as in these settings results are needed rapidly in order to give critically ill patients the urgent diagnosis they need; this will give the best chance of being treated and getting better, preventing mortality.
The POCT provides specific analyte testing, usually using whole blood samples, to give a diagnosis in a couple of minutes, this is either used as a way of monitoring a patient or aiding decisions made by clinicians for a patient diagnosis. The fact that the specific portable analysers simplify the testing procedure, by eliminating the preanalyitical preparation of samples, and supplying quick test turnaround times which is more convenient for the health care professionals as well as the patient, has resulted in point of care testing becoming increasingly popular and consequently increasing in use. The POCT can either give results quantitative e.g. blood glucose levels, or qualitative e.g. a colour strip used in urinalysis). Each gives clear indication of different bodily variables improving patient care and clinical performance. Although the information that can be obtained from a POCT is limited, compared to that of laboratory results, it is sufficient enough for the urgent information required in accident and emergency as well as in the home environment, hence the reason has to why POCT has become so important in the last decade.
Examples of testing
Blood Glucose Monitor
Blood glucose monitors have been used for many years now and have become more technologically advanced and effective with time. They are one of the most common tests performed at point of care, both in the hospital environment and also for blood glucose monitoring in the home.
There are three types of diabetes, type I, low blood insulin, type II, which is associated with obesity and occurs usually after the age of 40 and finally Gestational diabetes, an intolerance to glucose during pregnancy, each of these conditions is reliant on the use of glucose POCT to provide them with How To Perform A Blood Glucose Test Using A Blood Glucose Meterresults of the levels of glucose in the blood so that treatment can be administered to bring about normal blood glucose levels.
The test is conducted using a whole blood sample, which eliminates sample preparation time. Blood is usually obtained by a finger prick, manufactures usually guide that the second drop of blood be taken as the first drop may be diluted by tissue fluid. The blood is then placed onto a test strip and placed into the blood glucose monitor; a reading can then be obtained from the monitor as to the levels of glucose in the blood, as shown in figure 1.
Glucose monitors are also extensively used in emergency departments in hospitals to aid in glyceamic control and consequently decrease morbidity and mortality, by determining if a patient is hypoglycaemic, low blood glucose, or hyperglycaemic: high blood glucose. It is very important that these results are obtained immediately as if left untreated and undiagnosed it can rapidly lead to heart, kidney and brain failure. It is also very important to measure glucose levels during surgery as levels of glucose in the blood can sometimes rise through the operating procedure and consequently it is vital that clinicians are able to rapidly obtain results on blood glucose.
It is preferred to measure blood glucose levels at the point of care rather than in the lab, as in the lab results would be delayed, by sample preparation, labelling and transportation times along with the increased length of time the analyzers take to perform the test, by the time the patient got their blood glucose levels back it could be too late, time is of the essence in critically ill patients.
This type of test measures the clotting time of blood using the prothombin test time to measure the viscosity of the blood (Microvisk Ltd). The device usually analyses the extrinsic pathway of the clotting cascade (see figure 2), which is a series of reactions resulting in the formation of a clot, using micro chemical sensors to detect changes in free flowing blood to a clotting gel like substance. Blood is obtained from the patient by a finger prick or a venipuncture by syringe and inserted into analyser; an example of such an analyser is represented by (Figure 3)
The clotting of blood is a vital function of the body as a repair and defence mechanism as when a blood vessel is ruptured the amount of blood loss needs to be minimised so that the body can obtain the amount of blood needed to function properly. Patients which are in the operating theatre for surgery receive lots of blood which can lead to problems in coagulation, furthermore many medical conditions lead to people having to take anticoagulation drugs which prolong the time of clot formation, this needs to be continually monitored so that the dosage can be altered, especially in emergency departments so that blood loss is minimised and the patient does not bleed to death.
Due to the critical consequences that a delayed blood clotting time can have in emergency settings and in surgery, it is vital that results can be obtained rapidly to prevent the loss of too much blood, or the formation of too many blood clots, which could block the arteries and cause death. It is very important the correct drugs can be administered to the patient to prevent mortality hence why it is extremely valuable to have blood coagulation tests at the point of care.
Blood Gas Test
The blood gas POCT analysers the laboratory variables pO2, pCO2, pH, HCO3 as a measure of the acid and base balance of the body and also the partial pressures of gas exchange. These measurements are obtained to see if the patient is well oxygenated. Measuring the bodily pH determines if a patient is in acidosis/alkalosis. If the body is not receiving enough O2and is not eliminting enough CO2 from the body this results in a pH imbalance which can have severe consequences.
The test is conducted by taking a blood sample form the body either from a vein, artery or capillary, it is an important consideration has to where to collect the blood from as partial pressure of O2 and CO2 differ in capillary blood and arterial blood. The blood is then put into a cartridge which is then placed in the analyzer and then the blood gas results can be read, shown in (figure 4).
This test is very important in determining if the ventilator is giving the patient sufficient oxygen in intensive care units. It is also commonly used in emergency departs where there has been a neck or head injury, any sort of kidney problem or difficulty in breathing as these conditions would affect the partial pressures of gas in the body as well as the pH balance. There are also many illness which cause a bodily imbalance such as pneumia and also being over sedated by drugs), in these circumstances POCT are vital so that we can determine the amount of Gas exchange and pH balance of the body before bodily cells cease in function due to lack of oxygen or deviance in optimal pH; Consequently it is of vital importance that blood gas analysis can be performed at the patient bedside to get rapid results so that treatment can be administrated immediately.
The Advantages of Point of Care Testing
There are many advantages of POCT which is why in recent years they have become more and more popular and numerous in the hospital environment.
The most significant advantage of POCT over traditional laboratory testing is the rapid availability of results. This results in a decreased test turnaround time and ensures that a diagnosis can be obtained faster and treatment can be administrated as soon as possible ; This also reduces the length of patient stay due to immediate patient management and consequently adds to patient satisfaction and ensures less patient anxiety due to a decreased time in waiting for results.
The process of obtaining the sample is also simplified by the use of POCT because whole blood samples can be used rather than, for instance, blood plasma; hence the preanyaltical period is shortened as there is not a requirement for specialised preparation of the specimen, as you can see by (figure 5) the labour steps in laboratory testing as opposed to POCT is far greater hence the reason as to why laboratory testing takes a long time to produce the test results required.
Moreover only a small amount of blood is needed for a POCT so blood usage is reduced, this is vital in emergency situations when a patient may have lost a lot of blood. Also specimen transportations, handling and identification problems do not arise which is more convenient for the patients and the staff.
POCT can be performed by either a trained or non trained medical personal which means that the biomedical scientists can use more of their time more efficiently doing things which require their expertise such as the evaluation of results, rather than having their time consumed by sample collection and preparation.
Finally because laboratory results take a long time to obtain, it is evident that they reflect the past in terms of state of a patient's condition whereas POCT provides rapid results which can be continually monitored to give present updates of any changes in the condition of the patient (GUPTA.S 2004).
The Disadvantages of point of care testing
There have been many controversial debates into the analytical performance of point of care testing against laboratory testing. The fact is that Laboratory testing is conducted under strict standards of quality control and provides detailed analysis into the different laboratory variables, POCT do not have the same detailed standards with the same specialised error and analytical analysis from the expertise of the biomedical scientists and so people often question their reliability.
Also the POCT may be conducted by a non qualified personal who does not have the expertise or laboratory technique when conducting the tests and so may perform the tests inaccurately, or may not check that the instruments have been calibrated which would consequently give unreliable results.
Furthermore the POCT may end up economically stressing the national health service in the long run as they are very expensive to buy and do not achieve the economic scale of tests that a large lab analyser can (JAHN.UR 2003), POCT often can only conduct one test at a time whereas lab analysers can test hundreds of samples at a time whilst testing for more laboratory variables.
Finally POCT, often do not have the high technological data transfer systems and so the documentation of results is not has detailed and transferrable as the results from the machines in the laboratory, which is processed and stored on a computerised database and so data could easily be lost.