Review
Diagnostic point-of-care tests in resource-limited settings

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Summary

The aim of diagnostic point-of-care testing is to minimise the time to obtain a test result, thereby allowing clinicians and patients to make a quick clinical decision. Because point-of-care tests are used in resource-limited settings, the benefits need to outweigh the costs. To optimise point-of-care testing in resource-limited settings, diagnostic tests need rigorous assessments focused on relevant clinical outcomes and operational costs, which differ from assessments of conventional diagnostic tests. We reviewed published studies on point-of-care testing in resource-limited settings, and found no clearly defined metric for the clinical usefulness of point-of-care testing. Therefore, we propose a framework for the assessment of point-of-care tests, and suggest and define the term test efficacy to describe the ability of a diagnostic test to support a clinical decision within its operational context. We also propose revised criteria for an ideal diagnostic point-of-care test in resource-limited settings. Through systematic assessments, comparisons between centralised testing and novel point-of-care technologies can be more formalised, and health officials can better establish which point-of-care technologies represent valuable additions to their clinical programmes.

Introduction

Diagnostic technologies have improved substantially over the past few decades.1 In developed countries, laboratory testing has become increasingly automated, which improves reliability and reduces operator time. Diagnostic testing is now a fundamental part of medical practice, especially in the present era of drug-resistant infectious diseases. As turnaround times for laboratory tests shorten, and as laboratory results become increasingly integrated with electronic medical records, clinicians can receive test results even faster, which should improve care of patients and outcomes.2

Despite these advances, most advanced diagnostic laboratory technologies are centralised, and need highly trained staff and specialised facilities. The equipment is generally expensive and needs regular maintenance by skilled technicians. Consequently, many laboratory-based tests regarded as standard in developed countries are cost prohibitive and inaccessible to most patients and clinicians in many other countries.3, 4 In recognition of this disparity, WHO and others have called for new clinical diagnostic methods that can function in settings with restricted access to a central laboratory.5, 6, 7, 8, 9 By some estimates, the deployment of rapid, laboratory-independent diagnostic tests for just four infections (bacterial pneumonia, syphilis, malaria, and tuberculosis) could prevent more than 1·2 million deaths each year in developing countries.10, 11, 12

Diagnostic testing done at or near the site of care, called point-of-care testing, can provide results to a clinician without having to wait days or even hours for sample transport and laboratory processing.13 The point-of-care testing era began in 1962, when a new, rapid method to measure blood glucose concentrations14 was developed, and was bolstered in 1977, with the introduction of a rapid pregnancy test.15 Point-of-care testing in clinics and hospitals gained substantial traction in the early 1990s with the introduction of small, portable devices that could measure several electrolytes in emergency departments.16, 17 In the two decades since, many point-of-care tests have been developed. These tests now exist for many diseases and medical specialties, and are used in most medical contexts, from general outpatient clinics to intensive care units (panel 1).54, 55 In 2012, nearly 100 companies worldwide were marketing, manufacturing, or developing test instruments or reagents for use at the clinical point-of-care,56 suggesting that point-of-care testing, including novel nucleic-acid-based point-of-care tests, will become even more widely used.57, 58

The emergence of point-of-care tests has the potential to improve health-care services and patient-centred outcomes in diverse settings, especially those with poor health service or laboratory infrastructure.4, 59 Access to improved diagnostic technologies in resource-limited settings will bring unique challenges.60 The development and design of user-friendly devices, regulatory approval, and quality assurance programmes, and product service and support, all need to be addressed in novel ways.4, 58, 61, 62, 63, 64, 65, 66, 67 Moreover, to make prudent decisions about the introduction of new diagnostic technologies in resource-limited settings, decision makers need well executed studies on diagnostic accuracy, clinical effect, and cost.

We searched for and assessed reports containing definitions of point-of-care testing and studies of point-of-care tests in resource-limited settings. We found no consistent, formalised approach to assess point-of-care technologies in these settings. On the basis of this review, we provide a novel framework to assess diagnostic point-of-care tests in resource-limited settings to encourage standardised reporting of performance and effect, which should enable more direct and accurate comparisons between point-of-care technologies and their central laboratory-based counterparts.

Section snippets

Definition of point-of-care diagnostic tests

Several definitions of point-of-care test exist based on geographical, functional, technological, or operational contexts.68 An early definition was “a medical test that is conducted at or near the site of patient care”.13 Years later, another definition was “any test that is performed at the time at which the test result enables a clinical decision to be made and an action taken that leads to an improved health outcome”.69 More recently, experts on HIV and tuberculosis diagnostic testing

Studies of point-of-care tests in resource-limited settings

Many point-of-care tests have been designed for use in developed countries, and might not be readily transferable to resource-limited settings.4 When point-of-care tests are used in resource-replete emergency departments or intensive care units, the goal of point-of-care testing is to obtain immediate test results to help guide an emergent intervention. In resource-limited settings, where limited access to care is one of the major reasons for the failure of health services,73 point-of-care

Accuracy

As point-of-care testing expands into resource-limited settings, appropriate assessments of accuracy are essential. A fundamental criterion for success of any diagnostic point-of-care test is its accuracy and reliability.95 Studies of test performance might include sensitivity and specificity, positive and negative likelihood ratios, and positive and negative predictive values. These studies are usually the first and most common to appear in the scientific publications, and they estimate the

Discussion

The popularity and potential applications of diagnostic point-of-care testing in resource-limited settings have been growing and will probably expand. The aim of point-of-care testing is to provide a fast test result to clinicians and patients so that they might make an expedited clinical management decision, to improve outcomes for patients and overall public health.54 Improved outcomes can still be achieved at the expense of decreased test performance, if, for example, point-of-care tests

Search strategy and selection criteria

We searched PubMed from Jan 1, 1990, to March 31, 2013, with the terms “point-of-care”, “diagnostic tests”, and “resource-limited settings” for all available articles. We selected case reports, case series, epidemiological studies, and reviews of human diseases published in English. We also reviewed references from selected publications.

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