Q J Med 2001; 94: 571-573
© 2001 Association of Physicians
Editorial |
Point-of-care testing: no pain, no gain
Consultant Chemical Pathologist, Derriford Hospital, Plymouth
Consultant Biochemist, Dumfries and Galloway Royal Infirmary, Dumfries
Simple point-of-care testing (POCT) has long been a feature of hospital wards and general practice surgeries. Familiar examples include urinalysis, blood glucose measurement and ECGs. Increasingly, however, the range of tests that can be undertaken at the point of care spans the full gamut of clinical practice.1 Markers of myocardial damage can now be measured on admission in the assessment of patients with chest pain, both for diagnosis of acute myocardial infarction and for risk stratification. Measurement of D-dimers may permit more efficient triage of patients with suspected deep-vein thrombosis. On-site screening for microbial antigens or inflammatory markers such as C-reactive protein allows rapid determination of whether or not antibiotic therapy is appropriate, in advance of culture results. Screening for illicit drugs can now be carried out in the rehabilitation unit, or even in the workplace.
The benefits of POCT appear to be obvious. It bypasses all of the bureaucracy involved in ordering tests, arranging transportation, transmitting results and so forth. By doing so, it dramatically reduces the time required to get a result. At out-patient clinics and in some emergency settings, the ability to make all of the appropriate decisions at a single visit is of major benefit. For example, on-site measurement of glycated haemoglobin at diabetic clinics enables advice to be given to patients that is based on a current result. It is not surprising, therefore, that there are calls for clinical laboratories to address the needs that are so readily met by POCT.2 Strategic pathology reviews currently underway across many parts of England and Wales have arisen in response to current and projected future demands on pathology services; their aim is to ensure that these services have the capacity to evolve and incorporate new technological and manpower developments over the years ahead. These reviews present a timely opportunity for pathologists across laboratory disciplines to respond to increasing demands for POCT.
Is POCT too good to be true? How reliable is it? What happens when it goes wrong? More fundamentally, can it be shown to improve patient outcomes?
The immediate concern of most clinicians is that the results of any investigations performed at the point of care should be reliable. Reliability of results is normally ensured by quality control procedures. These involve the analysis of samples for which the correct result is known. However, traditional approaches to quality control may be costly and inefficient when applied in the non-laboratory setting.3 For example, in a hospital there will be multiple POCT instruments, each of which will usually have multiple operators. In addition, conventional quality control procedures are tedious and time-consuming, and may defeat the very purpose of POCT—convenience. Certainly compliance of clinical units with quality assurance programmes is often poor, and in some cases non-existent.4 An imaginative and practical approach to this problem is needed which recognizes that non-laboratory staff have other duties and different priorities. One such approach involves the regular sending of a separate, duplicate sample to the central laboratory for comparison with the POCT result.5 In this study, rogue POCT results were identified readily without the need for elaborate protocols, although the successful implementation of this approach depended on the existence of a team of staff dedicated to POCT. This approach has the major advantage of not requiring ward-based POCT staff to perform quality control procedures.
If a result produced at the point of care is incorrect, the worst-case scenario is that the patient suffers a serious or even fatal outcome as a direct consequence. In the US between 1984 and 1992, glucose meter failures were blamed for 24 deaths and 986 injuries, according to FDA data.6 In most instances, death or injury resulted from either the omission or institution of treatment on the basis of incorrect results. (Often incorrect results do not result in death or injury, because of the vigilance of experienced clinical staff. This emphasizes the importance of training in POCT, especially where turnover of staff is high). Clearly, patient care should be enhanced rather than compromised by the use of point of care testing, but the issue of what error rates are acceptable is a thorny one and there are no clear-cut answers.7,8 This relates in part to the paucity of data for comparison. Despite the topicality of safety issues (to which an entire issue of the British Medical Journal9 was devoted last year), the epidemiology of medical errors or adverse events in the modern NHS is largely unknown. This may change with the recent publication of the first preliminary estimates of the incidence and costs of adverse events in British hospitals.10 On a more general note, increasingly, public opinion influences both the definition of acceptable performance in the modern NHS, and the way in which health professionals monitor and regulate it. POCT will be no exception to this.
This brings us to the comparatively slender evidence base for POCT. It has been found repeatedly that merely moving testing from a central laboratory to the point of care does not guarantee improved outcomes.11–13 There are specific reasons why it may be difficult to prove that POCT can improve outcomes. If, for example, one is to show that measuring troponins at the point of care improves survival post myocardial infarction, then individual POCT results must be acted on promptly and in a standardized way. This may be difficult or impossible to achieve in practice. Even where POCT does show clinical benefit in one hospital or practice, it may not be valid to extrapolate the findings to other institutions. Differences in test requesting procedures, sample delivery systems, electronic data links and laboratory working practices combine to ensure that the context within which POCT is performed is rarely the same. Despite these difficulties, high-quality studies exist in the hospital setting,11–13 although until recently14,15 there has been an almost complete absence of rigorous evaluations of POCT in primary care.16 For those who wish to pursue the evidence-based route, it may be more fruitful to examine short-term ‘service’ outcomes that are more closely linked to the specific POCT activity, such as the time taken to get a result, than to focus on medical outcomes like decreased mortality or morbidity. The principles outlined by Rainey provide the most useful advice on how to design a manageable and meaningful outcome study.17
Once the decision has been made to perform a particular POCT activity, practical considerations will supervene. At corporate level, every hospital should have a POCT policy that aims to ensure that all POCT activity is regulated, and that all regulated POCT adheres to applicable statutory directives. At ward level, it makes sense to give ownership of specific aspects such as training, quality assurance, maintenance and so on, as well as overall responsibility, to named individuals. The degree of autonomy exercised over POCT by individual clinical units and consultants will vary both within and between hospitals. The general principle that should apply is that with control comes responsibility. POCT is above all a collaborative venture in which everyone must be prepared to pay the cost of convenience.
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