Point of Care Testing: Complementing the Laboratory

Point of Care Testing: Complementing the Laboratory

Point-of-care testing (POCT) is typically described as a clinical test which is done at, or close to, the physical location of a patient. This could be at a patient’s home, in a pharmacy, a GP’s office...

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Point-of-care testing (POCT) is typically described as a clinical test which is done at, or close to, the physical location of a patient. This could be at a patient’s home, in a pharmacy, a GP’s office or an in-hospital bed site. POCT typically consists of portable devices and instruments, which return results quickly. As a result, POCT permits immediate intervention or treatment.
POCT can also be defined usefully by specifying what it is not. In this case, a POCT is simply a test that is not analysed in a laboratory. POCT short circuits many steps involved in the latter. It eliminates the need to collect a specimen, transfer it to the lab, perform the test, and transmit results back to the provider.
POCT is increasingly used to diagnose and manage a range of diseases, from chronic conditions such as diabetes to acute coronary syndrome (ACS). Recent additions include genetic tests.

 

Driven by miniaturisation
The POCT era is considered to have begun in the 1970s, with a test to measure blood glucose levels during cardiovascular surgery. In 1977, a rapid pregnancy test called ‘epf’ became the first POCT for use wholly outside a hospital.
Since the late 1980s, one of the key drivers of POCT has been product miniaturization, with increasingly sophisticated and ever-smaller mechanical and electrical components integrated onto chips that can analyse biological objects at the microscale. The pace of miniaturization has accelerated at a breakneck speed in recent years, to mobile handheld and wearable POCT devices. These can be inte-
grated with other applications within a healthcare facility, or aid patients in monitoring and self-management of chronic conditions.

Wide product range, but handful of tests dominate
The most widely-used POCTs include “blood glucose testing, blood gas and electro-
lytes analysis, rapid coagulation testing, rapid cardiac markers diagnostics, drugs of abuse screening, urine strips testing, pregnancy testing, faecal occult blood analysis, food pathogens screening, haemoglobin diagnostics, infectious disease testing and cholesterol screening.” Nevertheless, just three tests - urinalysis by dipstick, blood glucose and urine pregnancy – are believed to account for the majority of POCT.

Comparisons with the lab
Beyond definition, the relationship of POCT to a laboratory is close for a very good reason. Most clinical cases for POCT use lab testing as a comparator. In other words, the first question that comes to many people when using POCT is whether its results match those of a laboratory. Although evidently quicker to obtain, is POCT as reliable? Another topic for comparison consists of the cost of POCT versus lab tests.

Costs: a vexed question

Even in the heady early days of POCT, there was awareness about potential cost downsides. One of the first efforts to address this question was a US study, published in 1994 in ‘Clinical Therapeutics’. [1] The study, by the Office of Health Policy and Clinical Outcomes at the Thomas Jefferson University Hospital in Philadelphia, sought to determine time and labour costs for POCT versus central laboratory testing on a cohort of 210 patients presenting to the emergency department.
The patients had blood drawn for a Chem-7 profile (sodium, potassium, chloride, carbon dioxide, blood urea nitrogen, glucose, and creatinine), or for cell blood count (CBC). Largely due to much quicker turnaround time (TAT), physicians reported that POCT would have resulted in earlier therapeutic action for 40 of 210, or 19 percent of patients. Costs for POCT were, however, over 50 percent higher, and also showed significant variability, depending on test volume. The authors speculated that increasing volumes of POCT would reduce costs “substantially.”

Volumes lower cost
The perception that POCT is much more expensive than a centralized laboratory persists. There are several reasons for this. Consumables generally cost more than tests done with automated laboratory instruments. On its part, POCT simply cannot achieve the scale economy associated with the latter. It also requires more staff downtime.
However, right from the early stages of POCT use, it seemed likely that unit costs could be reduced by increasing test volumes, as anticipated in the 1994 study by Jefferson University Hospital.
POCT was also to quickly demonstrate enhanced utility for certain kinds of tests. In 1997, a study at an Indiana hospital reported a near-halving in unit costs of panels, from USD 15.33 to USD 8.03, following POCT implementation for blood gases and electrolytes [2].

Levelling the field of play
One of the biggest hurdles in making cost comparisons of POCT with lab tests is the difficulty of levelling the playing field. It is also difficult to use such an exercise to draw generalised conclusions, since key conditions often vary significantly from one care facility to another. POCT is also complex to manage, and it is especially challenging to maintain regulatory compliance, especially in large institutions.
Though the cost of consumables is straightforward to determine, this is hardly so for labour.
Labour costs for a lab test are not limited to staff in the laboratory. They also include costs of staff in the pre-analysis phase, for phlebotomy, nursing and other services. Many of the latter entail administrative overheads. Typically, these would consist of formalities in the collection of phlebotomy supplies, the completion and submission of a test request, the labelling of tubes, specimen packaging and despatch.
In contrast, POCT eliminates most pre-analytic steps, along with associated staff costs and overheads. POCT can be undertaken by personnel who are not trained in clinical laboratory sciences.

Cost versus value
Although it seems to be common sense that POCT labour costs are significantly less than for a laboratory test, calculating this precisely requires a complex time-and-motion study which takes account of differences in wages and other costs for phlebotomists, nurses, administrative staff and medical technologists.
Unit product cost therefore reflects only a part of the overall equation, as far as justifying the case for a test is concerned. Indeed, many experts now urge for making assessments based on unit value rather than unit cost.

The role of TAT
With POCT, faster TAT promises better treatment, reduced patient stay, superior workflow and improved clinical outcomes. POCT is however less about reducing TAT than making results available in an optimal and clinically relevant time frame. This, in turn, is frequently dictated by conditions for which care is targeted as well as the setting in which it is delivered.
Delayed test results also impact upon cost in indirect ways. For instance, radiology departments use creatinine POCT before administering contrast agents, since patients with impaired renal function can develop contrast-induced kidney injury. This allows for quick decisions about patients and efficient use of costly CT scanners. If physicians had to wait for test results from a laboratory, the scanner would risk having to idle in a stand by status.

POCT can sometimes be only choice
Some tests have to be performed at point of care since there is no choice, in terms of time for transport to a lab.
One good example is an activated clotting-time test. This is used to monitor cardiac patients undergoing high-dose heparin therapy, whose blood immediately starts to clot after collection of a sample. Another is a POCT glucose test, where a quick result is crucial in determining insulin dosage for diabetic patients.
Elsewhere, whole blood cardiac-marker POCT tests in an A&E facility allow physicians to make rapid decisions on patients with acute coronary syndromes in terms of triage and disposition for observation, catheterization or transfer to a cardiac ICU.
Yet another example is a rapid flu test, used to identify patients who could benefit from antiviral therapy requiring administration as soon as possible after infection, in order to reduce symptomatic intervals. None of the above permit the wait times required for a lab test.

The grey zones
Still, there are grey zones where lab tests have advantages, which are non-negotiable under certain conditions.
One example is routine monitoring of international normalized ratios (INR) for patients on warfarin. The latter is used for prophylaxis against stroke and systemic embolism in patients with atrial fibrillation or mechanical heart valves. The goal of testing is to ensure that anticoagulant levels are appropriate. Over a certain threshold, there is a risk of bleeding, while below it, there is the danger of clotting.
While warfarin toxicity can result in life-threatening risk of bleeding, inappropriate warfarin dose reduction can lead to inadequate protection from a stroke or systemic embolism.
Lab-based testing entails the patient travelling to a GP, or having a caregiver come to take blood at the patient’s home, and doing this regularly. However, even a one-day TAT for the lab test can be a major problem in terms of warfarin dosage. The utility of POCT here seems clear. The GP can know the results and adjust the medication dosage immediately. In addition, POCTs can enable certain categories of patient to self-test and manage warfarin therapy.

Lab tests as gold standard
However, POCT tests can vary significantly from laboratory analysers. In the case of warfarin monitoring, this happens as INR values rise. Correction factors are also typically device- and institution-specific. They cannot be uniformly applied across institutions. Many clinicians therefore require POCT INRs which are greater than 5.0 to be confirmed with a venipuncture sample and a lab test.
Lab tests therefore remain a gold standard. Instrumentation in a laboratory provides robust analytics during a test, and includes a host of quality controls, from test strengths and timings to testing accuracy. These are incorporated into a laboratory information system (LIS) and stored in a patient case file. POCT simply cannot provide such a depth of information.

Gaps being closed
In brief, both POCT and laboratory testing have pluses and minuses. POCT provides definite advantages and reduce risk in some situations.
However, laboratory testing is more advanced, more closely follows scientific process and is fully integrated with the kinds of technical redundancies necessary to ensure greater accuracy and validation of records.
Nevertheless, gaps between the two are being closed, especially through software technology.
Some hospitals now have dedicated satellite labs in emergency rooms and outpatient facilities equipped with POCT.

 

[1]  www.ncbi.nlm.nih.gov/pubmed/7859247
[2] Bailey TM, Topham TM, Wantz S, et al. Laboratory process improvement through point-of-care testing. Jt Comm J Qual Improv 1997;23(7):362–80


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