Which of the following personnel has specialized training and will supervise the laboratory?

Abstract

Point-of-care testing (POCT) is laboratory testing conducted close to the site of patient care. POCT provides rapid test results with the potential for improved patient care. However, when incorrectly performed or inappropriately utilized, POCT can generate misleading results that require additional follow-up at increased cost and risk to the patient. While most POCT is waived under the federal Clinical Laboratory Improvement Amendments of 1988, there are several considerations that challenge its implementation. This chapter will focus on the advantages and limitations of POCT and will describe how to manage the quality of POCT in order to achieve optimal patient outcomes.

2.2 Point of Care Testing for Blood Gases

Point of care testing (POCT) has the potential to deliver rapid blood gas and other critical care test results in close proximity to the patient. When properly incorporated into the patient care process, POCT can translate to faster therapeutic intervention, reduced preanalytical errors, and improved patient care. However, POCT also requires a higher level of supervision and quality management to avoid the pitfalls of improper sample handling, test inaccuracy, training and continued competency assessment of nonlaboratorians, and justification of the additional costs of analyzers and test units or cartridges. The benefits of POCT are also dependent on the test volume and proximity of the care area to a clinical laboratory. For example, POCT becomes very labor intensive for high volume testing and may have limited benefit if a clinical laboratory is located near the patient care area.

Abstract

Point of care testing (POCT) devices are available for bedside or physician’s office testing of drugs of abuse using either urine specimen or oral fluid. Advantage of such testing is rapid availability of results. POCT devices utilize principles of immunoassay and lateral flow chromatography. For urine drugs screen, usually Substance Abuse and Mental Health Services Administration (SAMHSA) mandated cutoff concentrations for various drugs are used but there are exceptions. SAMHSA mandated guidelines are also available for testing of oral fluids. However, POCT devices may not be as reliable as laboratory-based drug testings as greater rate of falser positive and some false negative results may be observed using POCT devices compared to laboratory-based urine drug screening using immunoassays and automated analyzers. Nevertheless, POCT devices are gaining acceptance for drug testing in both urine and oral fluid due to simplicity of operation and rapid availability of results.

Introduction

Point-of-care testing (POCT) is now common in many near-patient and critical care settings. For blood gas and electrolyte testing, this includes operating rooms (ORs), intensive care units (ICUs), cardiac catheterization labs (CCL), emergency departments (ED), and many primary care clinic settings. POCT has several distinct benefits, such as minimizing or eliminating specimen transportation and processing which have the added benefits of minimizing preanalytical effects and providing faster turnaround times (TAT). Some systems offer a variety of test cartridges that provide a flexible test menu. More rapid test results potentially allow more prompt medical decisions, which can lead to improved patient outcomes, operational efficiencies, and patient satisfaction. For a variety of reasons, POCT devices usually require less blood volume especially compared to central laboratory requirements and can be especially attractive in pediatric areas (1). As POCT is not usually performed by trained laboratory personnel, maintaining regulatory compliance and quality assurance with POCT are challenges that require continual surveillance.

Most current POCT devices can be interfaced to both laboratory information systems (LIS) and electronic medical record systems (EMR). For today's current high test volumes and the need to minimize transcription errors, connection to information systems is essential. Well-functioning information systems can automatically transfer (download) results from the analyzer and display them to the physician. This ensures both accuracy and rapid delivery of results to multiple caregivers.

An issue that sometimes arises is the potential for POCT to replace central laboratory (CL) testing. POCT has, and will, replace some CL testing, with POCT accounting for 10%–20% of clinical laboratory testing, depending on the location. This is true where rapid results are essential for urgent decisions, and helpful in nonurgent settings such as clinics that potentially allow the physician to evaluate the results and discuss with the patient while still present. In addition, POCT can replace near-patient laboratories that are extremely inefficient. However, the sheer test volume handled by most central laboratories cannot be replaced by POCT, at least with present technology. Most, if not all, POCT devices are not equipped to handle large test volumes and generally would be far more expensive to operate.

Introduction

Point-of-care (POC) testing, also known as on-site or near-patient testing has enjoyed explosive growth during the last two decades because they are easy to use, require no sample processing, can deliver test results at patient bedside in a short time, and can be connected to Laboratory Information Systems (LIS). The POC tests have been used in testing for various disease states, involving chemistry as well as immunoassays. In 2011, POC market was estimated to be 30% of all diagnostic market. However, POC testing suffers from interferences the same way, if not more, as the Central Laboratory (CL) assays do. There are also controversies about whether or not using POC testing contributes to increased cost due to inadequate test utilization. In this chapter, several of the factors contributing to the methodological issues regarding POC testing will be covered. Whether POC devices are used in a clinical laboratory, emergency department, home testing, pharmacies, at accident scene, disaster recovery, physician's office, nursing homes, elder care centers, or a pain management clinic, understanding their performance and the nuances that can lead to serious errors is paramount for successful patient management.

Point-of-Care Testing Beyond the Laboratory

POCT beyond the laboratory is increasingly popular in some countries, and it is particularly useful when patients live a distance away from a hospital laboratory. Instrument manufacturers are now producing tabletop or handheld devices that are simple to use, autocalibrated, and require minimum maintenance. The haematology tests that are usually undertaken include haemoglobin concentration, blood cell counting by simple analyzers, erythrocyte sedimentation rate, and prothrombin time for oral anticoagulation control.37–40

Although this use of POCT is independent, the local hospital laboratory should encourage the doctors and clinics to seek advice and help with selection of appropriate instruments; their standardization/calibration; and quality control, including a link into the external quality-assessment scheme in which the laboratory participates. Harmonization of reports with laboratory records is helpful when a patient is referred to the hospital. Studies on the management of anticoagulation control have shown that with appropriate training and cooperation from the laboratory, pharmacists are able to provide as reliable a service as the hospital-based one and with more convenience for the patient.41

A major source of error in POCT outside the hospital is faulty specimen collection, whether for venous or finger-prick samples. Clinic staff who undertake this procedure should be given supervised training (see Chapter 1).

Point-of-care testing

Point-of-care testing (POCT), also known as near-patient testing, refers to any analytical test performed outside the laboratory and may be located either within a hospital as an adjunct to the main laboratory or for primary healthcare outside the hospital setting. The users of this service are often nonlaboratory staff. Public awareness of the availability of POCT has increased dramatically, and access to this technology has never been greater. When results need to be used for making rapid clinical decisions, laboratory testing within the clinical area may be the best arrangement for patients.

Diagnostic laboratories are often located in areas of the hospital that are remote from critical care and outpatient areas. Rapid transit systems, including pneumatic tubes (see earlier), may be the preferred alternative to multiple satellite testing areas, particularly when the main laboratory already offers a rapid results service. Knowledge of test turnaround time in the laboratory (see above) is required in order to make an informed decision on the need for near-patient testing in satellite areas. When POCT equipment is the preferred option, the running of the satellite laboratory and maintenance of its equipment should be the responsibility of the appropriate pathology discipline. The head of the haematology laboratory or a dedicated POCT co-ordinator should take overall responsibility for the service. This is essential for quality control, safety and accreditation, whether the satellite is staffed by laboratory staff, as in busy locations, or used by medical staff or nurses as a marginal activity. A designated member of laboratory staff should supervise this service, visiting each test location daily and ensuring that all results and quality control data are integrated into the main laboratory computer system. Guidelines on the organisation of a POCT service have been published by the British Committee for Standards in Haematology33 and the UK Medical Devices Agency,34 in the USA by the Clinical and Laboratory Standards Institute35 and internationally by the International Council for Standardisation in Haematology36 and the International Standard Organisation.37

1.2 Point-of-care testing

Point-of-care testing (POCT), often termed near-patient testing or bedside testing, is an alternative diagnostic approach to laboratory analysis [25]. Generally, POCT is conducted near the patient and the results are acquired within a short period of time (ideally < 20 min). This rapid format is less resource-intensive than laboratory testing and centers on the availability of highly developed point-of-care (POC) devices to permit specific biomarker detection in a robust and simplified manner. These devices can be in the form of a single disposable element or incorporate an entire platform that accepts disposable inserts. The platforms often consist of dedicated control and reader systems and include disposable cartridges for sample loading. Moreover, adapted laboratory assay elements and tailored structures are typically packaged in a condensed and highly coordinated configuration within these cartridges to facilitate automated sample analysis. This automation is fundamental to the versatility of POC devices and the capacity to support simplified measurement of biomarkers from complex samples. To a certain extent, an element of mistake-proofing is also incorporated within the design of these platforms to mitigate against improper operation. In contrast to the operation of sophisticated laboratory instruments, this aspect is influential in minimizing the need for highly specialized training to use these devices. Furthermore, these devices can be utilized in a variety of environments that could further enhance the recognition and ongoing management of CVDs (Table 1).

Table 1. Suggested sites for point-of-care testing of cardiovascular disease biomarkers.

Certain locations may be more suitable for the use of these rapid sample-to-answer assays for AMI diagnosis, with others being more appropriate for the measurement of cardiovascular risk biomarkers. The ED is a fitting setting to conduct POCT providing it is structured and implemented accordingly, with inefficient operational strategies limiting the efficacy of POCT in these settings [26]. Point-of-care testing of cTnI has been shown to reduce the test TAT in comparison to laboratory assays [27], with one study demonstrating that the average LOS for ACS patients admitted to hospital in an ED was reduced by over 25% [28]. Additional pressure can also be alleviated from the central laboratory if POCT is implemented in judicious settings. This was demonstrated by Singh et al. in a medical center which involved the re-structuring of the central laboratory testing paradigm in conjunction to deploying auxiliary diagnostics to significantly reduce the average laboratory testing TATs [29]. They performed different types of POCT in various locations such as the intensive care unit, the radiology lab and the ED (cTnI) which contributed to notable improvements in the average laboratory testing TATs. In addition to presenting as an alternative to laboratory analysis, POC devices can be utilized in central laboratories, although, this may somewhat contradict the concept of POCT. Nevertheless, this was a critical element within the re-organization of a central laboratory in an effort to achieve higher efficiencies and reduced TATs [30].

In settings such as rural health clinics, POCT is a pragmatic alternative to sophisticated centralized laboratory analysis. Immediate access to central laboratory facilities or the ability to determine the severity of myocardial injury is often unfeasible and limited in sparsely populated regions. The use of POCT in these settings helps discern patients that require acute care [31]. Conversely, the capability to accurately measure cTn in rural centers can reduce unnecessary transfer of patients to larger clinics or EDs, thus improving operational efficiency [32,33]. This form of testing is also highly beneficial in clinics without 24/7 laboratory facilities, again supporting the identification of acute cardiovascular injuries in locations that would otherwise have to request for a transfer [34]. Measuring cTn prior to hospital arrival can also support a diagnosis of AMI, especially in high risk patients [35,36]. This implies that the emergency medical service performs POCT in ambulances. Time to first cTn measurement is thus considerably shorter in comparison with general procedures that would typically involve sending a sample for laboratory analysis following hospital arrival [37]. The time to hospital admittance or discharge can also be reduced, however POCT in emergency medical vehicles is limited by the relatively short period from symptom onset to cTn measurement. This often inhibits a definitive diagnosis due to the low concentrations of cTn found in circulation in the initial hours following an infarction [38]. Moreover, this is compounded by inferior performance characteristics of cTn POC assays when compared to their laboratory assay counterparts [39]. Van Dongen et al. encountered this issue when measuring cTnT in stationary ambulances using Roche's cobas h232 POC system approximately 85 min following symptom onset [40]. The authors could adequately determine NSTEMI in high risk patients, however they recommended acquiring a second cTnT measurement 120 min or more from symptom onset to further elucidate the severity of a patient's condition. This study demonstrated that measuring cTnT in ambulances could assist in predicting major adverse cardiac events and rule in high risk patients, thus expediting patient treatment. However, sensitivity and accuracy limitations of the POC assay essentially prevented a definitive diagnosis for the majority of patients.

Similar concerns regarding performance limitations are shared among GPs assessing POCT in primary care, with many considering the clinical utility, diagnostic accuracy and quality assurance of the devices as principle barriers to implementation [41–43]. There is however an acknowledgment that POC cTn and b-type natriuretic peptide (BNP) assays are desired in primary care [44–46]. Similarly, one of the main benefits from these tests would be to reduce unnecessary hospital referrals by ruling out myocardial injury [47]. However, only in specific circumstances; such as for patients whose symptoms resolved at least 12 h prior to measuring cTn or if symptoms are ongoing for over 24 h, should POC cTn assays be used to safely rule-in/rule-out AMI in general practice [48,49]. Moreover, if the patient displays symptoms that developed within 24 h and/or an abnormal ECG is observed, it is advised that cTn should not be measured and the emergency medical services should be requested immediately [11]. This illustrates the ongoing dilemma of measuring AMI biomarkers in primary care and the case for POCT. Additionally, beyond the potential hazards of diagnosing AMI in settings that are unfit to perform revascularization, the inadequate performance characteristics of POC cTn assays—chiefly the limited diagnostic sensitivity and broad analytical variability—suggest widespread implementation will be restricted until POC assays with improved performances are commercially available [39].

Terminology

Point-of-Care Testing (POCT) is defined as laboratory testing conducted close to the site of patient care, typically by clinical personnel whose primary training is not in the clinical laboratory sciences, or by patients (self-testing). POCT refers to any testing conducted outside a main, central, or core laboratory setting. Other common terms for POCT are ancillary, bedside, decentralized, near-patient, patient-focused, peripheral, portable, and satellite testing. Some of the terms may be more general in meaning, as ancillary or peripheral testing can describe any testing outside of a main laboratory. Other terms are more specific, like bedside testing that describes testing conducted solely at the patient’s bed. The multitude of words used to describe POCT adds confusion. In general, discussions of POCT should limit the number of terms and always define the exact meaning whenever changing POCT terminology.

Point-of-care testing

Point-of-care testing is appropriate in some clinical situations since the availability of a plasma drug concentration at the time of consultation allows the clinician to make immediate decisions on dosage adjustments based on objective data. The savings in patient time and improvements in clinic throughput have been shown to outweigh the extra costs of on-site testing in a number of settings. Several methods are available for on-site TDM testing, but need to be carefully evaluated to ensure that their analytical performance is adequate in the setting in which they are used.