Point-of-care tests for rapid detection of respiratory tract infections are emerging on the market. We explore how these products compare with those of bacterial culture for detecting streptococcus infections with Pentti Huovinen, dean of medicine at the University of Turku, Finland.
Practical Patient Care: Please Introduce yourself and explain your roles and responsibilities at the University of Turku.
Pentti Huovinen: I am the dean of the medical faculty at the University of Turku. In addition to that, I have worked for more than 20 years at the National Institute of Health and Welfare as physician in chief and research professor, studied at the Harvard Medical School in Boston and at the Wharton School in Philadelphia.
My main research interests are antibiotic resistance, surveillance of resistant bacteria, antibiotic use in the community including diagnostics and various health aspects of human microbiota. In 2008 I received the award of excellence from the European Society of Clinical Microbiology and Infectious Diseases, and in 2009 I was president of the 19th European Congress of Clinical Microbiology and Infectious Diseases (ECCMID) in Helsinki, Finland. I have studied diagnostics of respiratory tract infections, epidemiology and treatment of pharyngitis, otitis media and other community-acquired infections for more than 25 years.
What is group A streptococcal (GAS) disease, how common is it, and what symptoms does the affected patient present?
Group A streptococcus is a bacterium that causes mainly pharyngitis and skin infections, but also life-threatening septicaemia. Pharyngitis caused by GAS, and skin infections like impetigo, are most common in children aged from five to 15. Erysipelas is more common in adults and aged people. GAS sepsis can progress rapidly, and in the worst case scenario lead to death within 36 hours. It has been called a flesh-eating bacterium.
Why is a prompt diagnosis of GAS important?
GAS pharyngitis and skin infections can be treated with penicillin or first-generation cephalosporins. Specific bacterial diagnosis always leads to the best antibiotic choice and treatment result.
Why is diagnosing respiratory infections challenging?
In Europe, we use hundreds of millions of antibiotic courses annually. Two thirds of these are used in the treatment of respiratory tract diseases and almost all are prescribed without any idea of causative microbial pathogen. Antibiotic resistance is among the most challenging health threats of society. Thus, we need better diagnostic measures to guide antibiotic use in the community. However, to be a true point-of-care test that has importance in antibiotic choice or in avoiding antibiotic treatment, the result has to be received in 20 minutes or less.
There are hundreds of different viruses and tens of different bacteria that cause upper and lower respiratory tract infections. Although patient investigation is always the most important in clinical practice, specific microbial diagnosis will help a lot in treatment decision-making. Thus, we need rapid and reliable point-of-care tests to identify the causative microbial pathogens among all commensal or by-standing bacteria. So, it is challenging to develop these kinds of tests.
How have diagnostic processes for respiratory infections evolved in the past 20 years?
When I began my career more than 30 years ago, rapid tests were a dream. Bacterial culture was practically the only way to get GAS diagnosis. It took two days or sometimes even longer to get the results.
Rapid GAS antigen detection tests came to wider clinical use about 20 years ago. Today, these tests are pretty reliable and we do not confirm negative antigen test results by bacterial culture anymore. However, because the prevalence of GAS varies a lot, most of the test results are negative. Even in epidemic situations, no more than 20% of GAS tests are positive. Thus, these tests are very often not used. In addition to GAS, I expect to get specific viral diagnosis, for example, in the case of pharyngitis and otitis media. Positive viral diagnosis makes avoiding unnecessary antibiotic treatments easier.
What are point-of-care devices for these purposes, and how do they work? How do they compare with traditional culture methods? What experiments have been conducted to test this? What were the conclusions?
There are very few, broad-range microbial diagnostic tests on the market. The tests are not rapid enough, expensive and usually lack some important microbial pathogens. Most rapid tests are antigen-detection tests, and specific antibodies, such as rhinovirus, have been lacking from these sets.
PCR based tests are slower but the speed is improving. All these tests are much faster than traditional bacterial culture and often more sensitive. However, there are no wide clinical studies on how broad-range viral and bacterial point-of-care tests influence antibiotic prescription.
What do healthcare workers and patients think of point-of-care devices?
In the Department of Paediatrics at Turku University Hospital, physicians or nurses insisted keeping the mariPOC respiratory tract virus test to identify respiratory tract pathogens, especially in influenza and respiratory syncytial virus patients. Also, parents of children are satisfied to get to know the real causative viral agent and accept the decision not to prescribe antibiotics.
My dream for decades has been to collect enough online data from our university hospital so that every morning when physicians are opening their computers, they get prompt information of the microbial epidemic situation in their region.
Are there any disadvantages of using point-of-care tests when diagnosing respiratory infections?
There are still too few real point-of-care tests available and there is a lack of clinical trials to identify disadvantages of these tests. At this stage, the positive expectation to get more information to guide antibiotic use is at a high level.
What’s in the pipeline for these devices? How likely are they to become mainstream in hospitals in Europe?
There are great expectations in hospitals and communities, but no good solutions yet. The European Commission has promised to pay €1 million to a person or study group that develops a rapid diagnostic test that improves antibiotic prescription
The US has made a better offer.
As a part of the national strategy for combating antibiotic-resistant bacteria, the US Department of Health and Human Services (HHS) announced a prize for the delivery of one or more successful rapid point-of-care diagnostics that may be used by healthcare providers to identify bacterial infections. The prize will be up to $20 million, subject to the availability of funds.
To what extent will point-of-care devices be the future of bacterial infection diagnosis?
I trust combined bacterial and viral tests. Otitis media is most often of bacterial and viral origin. Thus, specific microbial diagnosis may not be enough to make correct decision to prescribe or not prescribe antibiotic treatment.
We need more clinical data that combines clinical and microbial diagnostics and long enough follow ups. I am very positive, and trust engineers and inventors to develop dream machines that will help physicians to make correct antibiotic prescription decisions.
