Laboratory strategies: meeting the increasing demand for point-of-care diagnostics

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,¹ 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.² 

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,³ there are millions of flu tests administered.⁴ 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.⁵ 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.⁶ 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.⁷ 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.⁸ 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.⁹ 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.¹⁰ 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.