By Prof Leo Yee Sin, Executive Director, National Centre for Infectious Diseases
Point-of-Care
Testing (POCT) generally refers to testing that is done near a patient/person
outside of the laboratory, with the results to be acted upon, including
potential change in the care of the patient/person. It can be performed by
personnel who are not laboratory-trained or by the patient/person himself/herself
(self-test), and at multiple locations, such as his/her bedside at the hospital,
the emergency room, the intensive care unit, the clinic, in the ambulance, or in
the comfort and privacy of his/her home.
History of POCT
In the early days of medicine, almost all tests were done in central laboratories that typically managed hundreds to thousands of samples. But this posed some challenges to healthcare professionals, including having to transport the samples from remote areas, and the subsequent wait for results which could take up to several days or even weeks. Such challenges prompted the need to develop faster tests that can be done near the patient and where results can guide immediate medical interventions.
In recent years, POCT has become a fast-moving field driven by unmet healthcare needs and the rapid advancement of technologies. Today, POCT spans many areas of medicine, and some of the most commonly known POCTs include pregnancy test, and blood sugar test for diabetes. POCT is also being used to detect elevated levels of heart enzymes in cases of suspected heart attack, as well as to detect inflammation markers during an infection or to diagnose rheumatic diseases.
Benefits of POCT
As the tests are done near a patient/person, one key benefit is having a rapid interpretation of the results to support decision making regarding his/her care. Other benefits include readily available self-test kits with better access to them, ease of use, safety, low costs, and the ability to self-monitor. Another advantage is that many different body fluids such as blood, urine, saliva, faeces, nasal and throat swabs can be tested.
However, while many POCTs are designed to be relatively simple and low-risk to use, they are not entirely error-proof. Sensitivity can be compromised due to operator unfamiliarity, inherent nature of the test, and the prevalence of the disease at the time of testing. Therefore, results need to be interpreted appropriately.
POCTs for Infectious Diseases and COVID-19
As an Infectious Disease specialist, I have seen the exponential growth of infectious disease testing of POCT in recent years. For a febrile, unwell patient, the tests are intended to: diagnose infections quickly, allow for timely treatment, limit the spread of infection, and bring an epidemic under control. One POCT which everyone is familiar with is the Antigen Rapid Test (ART) for COVID-19. It is strip-coated with antibodies in a cassette to allow nasal secretions mixed with the buffer solution to flow through. Two lines will appear if the sample contains COVID-19 antigens, denoting a positive result. The two lines consist of a control line marked 'C' to ensure the validity of the test strip, and a test line marked 'T' to indicate the result. The entire test typically takes between 15 and 30 minutes.
Another POCT used for COVID-19 is the pulse oximeter, which measures blood oxygen levels. The device enables a patient to self-monitor his/her condition at home. Simply clip the oximeter on to any finger or thumb, and it will show one's oxygen level and pulse rate. A pulse oxygen level of 95 per cent and above is considered adequate, whereas a reading of 93 per cent and below could require urgent medical attention. Readings of any level between 95 and 93 per cent indicates that the patient should closely monitor his/her condition or seek early medical assessment.
Apart from COVID-19, POCT is used in other infectious diseases such as human immunodeficiency virus (HIV) and Streptococcus infections. The Ministry of Health (MOH) and National Centre for Infectious Diseases (NCID) launched a HIV self-testing pilot programme in August 2022, which complements widely available tests at healthcare institutions. This POCT provides an avenue for individuals to test and to repeat the test if necessary in private through the use of an oral swab, and the results can be obtained within 20 to 40 minutes. Those who test positive should visit a healthcare provider to confirm the diagnosis and be referred for treatment. HIV is a very treatable disease, and early detection and treatment is key to achieve the best outcomes and halt further transmission of the disease.
For Streptococcus infections, a less locally-known but widely used POCT in the West is the rapid strep-throat test. Strep-throat is caused by Streptococcus group A bacterial infection of the throat, and is a common infection among children. Unlike most upper respiratory infections which are caused by viruses, strep-throat is treated with antibiotics as it is a bacterial infection. While serious complications are rare, they can occur without treatment and include, rheumatic fever (i.e. a disease that can affect the heart and joints) and post-streptococcal glomerulonephritis (inflammation in the kidneys).
Unmet Needs in Infectious Disease Management
There are currently two areas most in need of POCT. Fever is among the most common symptoms of infection, yet not all fevers are due to an infection, and not all infections are caused by bacteria and require treatment with antibiotics. To-date, there is no simple, accurate, 'catch-all' marker which can detect the cause of a fever via testing a drop of blood or other means to rapidly diagnose the above. Therefore, it is not uncommon for clinicians to err on the side of caution, and prescribe antibiotics as a treatment. However, this can inadvertently hasten the development of multi-drug resistant bugs.
Another area is the rapid detection of drug resistant bacteria to guide optimal antibiotic treatment, either at General Practitioner clinics or hospitals. When facing a patient with sepsis, and where every minute counts to save his/her life, most clinicians would empirically start broad and higher-end antibiotics. This can result in the overuse of high-end last resort medication, which can fuel the emergence of super-bugs with very limited treatment options.
Future of POCT
New advances in POCT devices are emerging from lab-on-a-chip technology. These miniature devices are designed to rapidly automate every step of a laboratory test using a very small sample volume, without the need for manual handling of the sample. They are technologies with a flexible platform that can rapidly be modified to suit novel pathogens. I envisage such technologies to manage rapid triage at emergency rooms or screening centres, to reduce waiting times, and the risk of cross contamination during an outbreak. Other innovations include smartphone-based technology and wearable technology, as well as the integration of artificial intelligence, machine learning and neural networks into POCT.
The article was also published in Lianhe Zaobao on 11 April 2023.
