Point-of-care testing: filling the diagnostic gaps in tropical medicine?

Abstract

Many infectious diseases require timely diagnosis and early appropriate treatment to prevent death and sequelae. The clinical management of patients suspected of having serious infections often consists of providing empirical treatment that targets the most relevant conditions while waiting for aetiological results obtained within hours, days or weeks by conventional microbiology. This strategy requires comprehensive epidemiological information, good clinical skills, and adequate laboratory facilities, and leads unavoidably to missed diagnoses on the one hand and unnecessary prescriptions on the other. In the past decade, major efforts have been made by the scientific community and industry to bring diagnostics closer to the care provider and to the patient. The concept of point-of-care (POC) testing has emerged for infectious diseases, as reviewed in a previous themed section of Clinical Microbiology and Infection [1–3]. Although no universal definition exists, POC testing refers to any diagnostic technique used at or near the patient and providing results within a very short time frame in order to allow decision-making (triage, referral, and treatment prescription or withholding) ‘during the same clinical encounter’ [4]. POC testing in developed countries may therefore comprise very diverse technologies (from simple immunoassays to more sophisticated nucleic acid amplification tests), users (lay persons to highly trained staff), and settings (homes to ‘near-care’ reference laboratories). In the deprived settings of developing countries, this need for rapid diagnostic testing is even more pressing, because patients often seek care late and cannot easily come back to obtain results and specific treatments [3]. Major patient and health system delays are observed before diagnosis [5]. To be effective in poorly staffed, ill-equipped tropical settings, POC tests should ideally meet the ‘ASSURED’ characteristics —affordable, sensitive, specific, user-friendly, rapid and robust, equipment-free, and delivered—according to international recommendations issued about ten years ago [6]. For the time being, almost only lateral-flow immunochromatographic assays fulfil these stringent technical requirements, and other formats, requiring multiple steps or cold chains (flocculation, agglutination, and vertical flow-through immunochromatography), are progressively being abandoned. In tropical settings, the so-called rapid diagnostic tests (RDTs) are now almost exclusively such immunoassays, which are usually performed near the patient in primary-care laboratories, although some of them, e.g. for malaria, are increasingly being used in the community as well. Field diagnosis of malaria or human immunodeficiency virus has been greatly simplified over the past decade by the development of these RDTs, and countless commercial kits are now available at reasonable cost. More recently, major progress has been made for other infections, such as dengue and syphilis, and new tests are regularly being evaluated or entering clinical care. This themed section is aimed at reviewing current RDT development and perspectives for several major clinical