CENTRAL LABORATORY
ROLE: TO COPE WITH DEMAND FOR POC
The healthcare landscape is undergoing
dramatic changes: hospitals are consolidating into regional networks with
highly specialized medical care performed in core facilities, generalized
medical care provided in satellite hospitals, and ambulatory services offered
at point-of-care (POC) locations.
Diagnostic laboratory testing is
undergoing a similar transformation. Complex, non-urgent tests are performed in
core facility laboratories or in reference sites; routine, acute diagnostic
tests are performed in core laboratories or in satellite hospital facilities;
and point-of-care testing is performed in outpatient clinics, physician office
laboratories, retail clinics, and in-home testing. With an increased effort to
provide cost-effective, timely medical care for ambulatory patients, patients
are seeking treatment at local physician offices and retail clinics at a rate
higher than ever before, and POC laboratory testing has become one of the
fastest areas of growth in the medical field, with the number of tests
increasing at an estimated 10% to 12% annually.
The transformation of POC testing is
not without challenges. Testing has to be accurate, technically uncomplicated,
inexpensive, and actionable. It is also critical to note that, particularly in
the POC arena, lab tests play a role much larger than identifying or isolating
disease-causing organisms. These tests are the start of an end-to-end chain of
care that provides timely information to providers and determines patient
outcomes. Accurate results are critical to ensuring antibiotic stewardship,
initiating prompt and appropriate treatments, and preventing unnecessary
auxiliary tests. These results inform the provider’s treatment decisions and
allow for immediate action. Thus, as techniques are enlisted to ensure
appropriate procedural characteristics to meet POC demands (e.g., turnover
time, implementation cost, etc.), the effectiveness of each test must continue
to hold equal importance.
An additional challenge for POC
testing is somewhat unique—the accommodation of seasonal variation in test
volume. Hospital-based laboratories provide a broad menu of diagnostic tests
and have a proportionately large technical staff available to meet the testing
demands. During peak test volumes for diagnostic services, the laboratory has
the flexibility to adjust staffing to meet these needs. In contrast to this
situation, POC testing sites generally have minimal staffing to perform tests,
and the service providers (e.g., technician, medical assistant, secretary,
nurse) will frequently have other responsibilities. Thus, the heavy influx of
POC testing that occurs at certain times of the year yields an exceptionally
high demand for on-location diagnostic tests.
As a result of the increasing mandate
for POC testing, there is a need for laboratories to implement strategies that
accommodate quick turnover in large volumes; labs must not only ensure that
there are enough tests available at all times, but also ensure that newly developed
tests are suitable for procedural operations at POC locations and meet the end
goal of prompt and quality patient care. Diagnostic tests for influenza virus
are a noteworthy example of the tremendous burden on labs and healthcare
providers every year. In the traditional flu season, which lasts from October
to March, there are millions of flu tests administered. Not only does this
yield a higher-than-average demand for almost half of the year, but this demand
is being realized almost entirely at POC locations. The majority of symptomatic
patients go directly to their local physician office at first sign of illness.
As a result, it becomes even more critical for front-line providers and their
lab partners to weigh the benefits of various POC diagnostics in order to
handle such a high volume of tests in a compact timeframe.
Influenza diagnostics has undergone
dramatic changes in the past decade. Historically, in vitro viral
culture was the most sensitive available test, but this could only be performed
in hospital-based laboratories, requiring specialized technical expertise and
testing facilities, and results were not available for a number of days. Thus,
this testing was confirmatory and not particularly helpful for the management
of acute infections. A transformation occurred when real time nucleic acid
amplification tests (e.g., real time polymerase chain reaction, RT-PCR) became
available. These tests are now the gold standard for detecting influenza virus
in clinical labs, as they have shown high sensitivity and specificity. However,
on the procedural level, these tests do not lend themselves to operational
compatibility at POC locations. Commercially available RT-PCR tests have a
turnaround time of one to six hours and are run frequently in batches, which
can further delay results. Additionally, although testing has been greatly
simplified with the introduction of commercial platforms and diagnostic assays,
testing is still generally restricted to hospital-based laboratories and has
not been extended to POC facilities.
The solution for POC testing lies in
the development of immunoassays for the detection of influenza antigens. In
principle, immunoassays offer solutions to the procedural limitations of PCR
tests; commercial immunoassays for influenza virus have a turnaround time of 15
to 30 minutes, require much less costly equipment, and are generally easy for
point-of-care providers to operate. However, the accuracy of the
first-generation tests has been appropriately questioned. The most common tests
show only 10 percent to 70 percent accuracy based on the commercial assay and
circulating strains of influenza virus.8 The majority of these tests
use a manual visual read system for results in which the user determines assay
results by reading an output of colored lines to indicate a negative or
positive sample. The inherent subjectivity of such readings has been shown to
result in user variability and error rates as high as 56 percent. Thus, while
operationally these tests are a good fit for POC locations handling either
small or large volumes of tests, they fall short in facilitating the end-goal
of POC testing, which is to help providers make accurate diagnoses. Instead,
providers find themselves torn between incurring additional costs by requesting
repeat samples, and making actionable decisions based on an uncertain result.
Many believe that the best strategy to
fulfill the need in point-of-care testing is to commit to meeting both
procedural and quality standards in lab diagnostics. A newer generation of
tests—digital immunoassay rapids (DIAs)—is designed to meet such requirements.
Built to handle large volumes of tests in a short period of time and integrate
into larger output systems, DIAs are a promising solution. By offering an
instrument-based, digital read-out test that can be measured objectively and
using immunoassay crafted particles and antibodies, these tests ensure precise
detection and have been shown to be nearly as accurate as PCR. Digital
immunoassays take just over 10 minutes, and some are CLIA-waived. Current
systems, and similar systems in development, have the potential to help lab
operations align with the shift to POC occurring in clinical settings. The
rapid turnover between test times and ability to be easily used by many locations
and providers allow the physician network to handle high patient volume.
Providers can then consider the option of initiating treatment early in the
infection, when it has the best chance of being effective and leading to
successful patient outcome.
Ultimately, the shift toward
point-of-care diagnostics is positive: the more access people have to quality
local care, the more likely they are to be seen when needed, and the less
likely they are to receive unnecessary and costly tests—all of which will inevitably
result in a positive impact on patient health. The laboratory is in many ways
the start of this chain of care. Thus, it is critical that diagnostics continue
to be developed to adequately equip POC sites with the tools they need to meet
a high and timely demand. By strategically incorporating procedural and
functional elements, diagnostic providers can ensure that tests are capable of
performing at the level and frequency necessary to function in point-of-care
and provide patients with the most convenient, quality care possible.
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