Multiple Choice

By Jim Poggi

Which tests your customers should consider, and why

According to the Centers for Disease Control and Prevention (CDC) influenza season data from 2017-2018, the positivity rate for flu tests performed in the United States was only 15%. It ranged from a low of 13.4% in one region, to a high of 25.5% in another.

These tests were all done on patients with upper respiratory infections, fever and other symptoms classic of influenza. And, due to flu re-classification and introduction of multiple new molecular and reader based flu tests, test methods have never been better. Even with the flip of a coin, you have a 50% chance of being right. From that perspective, being right 15% of the time does not seem to be especially impressive. And, as account managers, we and the suppliers we support invest a lot of time and energy into flu season, from providing vaccines to selling flu and other test kits to supporting and gaining revenue from the far higher customer spend on exam room and hygiene supplies during a more severe season. So, it pays to know what’s going on and to be able to articulate it to our customers in a meaningful way.

Since the lab technology behind flu and other respiratory test kits has improved dramatically over the past ten years, and the number of new tests is also growing quickly, we owe it to ourselves and our customers to engage in new thinking and challenge which tests they should consider and why. I’m providing some thoughts for you to consider.

Flu in the broader context
Why was the positive flu test rate so low? First of all, we need to remember that flu does not take place in isolation. Typically, many infective agents circulate at the same time flu peaks in the late fall through early spring in the United States.

It’s more appropriate to think of this time of year as “upper respiratory disease season”. This change of focus broadens our thinking and allows us to help our customers think in more global terms than just flu, or just flu and strep. There are over 25 different causative agents circulating at the same time as flu, so, in theory at least, the chance of “it being flu” is actually closer to 4%. However, the symptoms of respiratory severity vary, and initial patient presentation does provide some clues whether the disease is flu, strep or another agent.

Is lab technique a reason for the lower than expected number of positive flu tests?
While molecular tests are far less susceptible to a poorly performed swab with a low yield of virus or bacteria, a good swab is table stakes for a proper diagnosis. We need to remember that non-molecular lateral flow and reader based tests still represent over 50% of all flu tests performed in the United States, so a good swab is a critical requirement for a proper result.

How does the number and type of other upper respiratory infection agents influence diagnosis?
As reported by the CDC and others, about 98% of all upper respiratory infections are caused by viruses, not bacteria, so correct differential diagnosis is important to patient health, and to prevent unnecessary antibiotic prescriptions and foster better antibiotic stewardship. While there are no CDC surveillance statistics for group A strep infection, avoidance of complications including rheumatic fever, rheumatic heart disease, development of pneumonia and sepsis make an accurate and timely diagnosis critical.

CDC provides an excellent resource you may want to share with your key customers when discussing respiratory season and which tests to choose. Their webpage is entitled “Unexplained Respiratory Disease Outbreaks” (URDO) and has a great deal of valuable information including a list of the most common respiratory pathogens and recommended differential diagnosis approaches. The link is below:

https://www.cdc.gov/urdo/index.html

A representative sample of some of the more serious causes or upper respiratory infection

Causative Agent	Treatment Plan Impact	Possible Outcome Improvements
Group A streptococcus	ü prescribe antibiotic or not ü isolate patient	· Prevent rheumatic fever and complications · Untreated may lead to sepsis
Influenza	ü prescribe antivirals üother supportive treatment üisolate patient üimmunization opportunity	· Shorten duration of disease · Prevent complications such as pneumonia
Respiratory Syncytial Virus	üfluids and supportive treatment	· Prevent serious complications especially in younger children
Bordetella pertussis	ü supportive treatment üimmunization opportunity	· Avoid development of pneumonia
Mycoplasma pneumoniae	ü supportive treatment	· Avoid development of “walking pneumonia” or arthritis
Adenovirus	üsupportive treatment üantiviral in rare instances for immunocompromised patients	· Supportive treatment only
Coronavirus	ü supportive treatment	· Supportive treatment only
Parainfluenza viruses	ü supportive treatment	· Supportive treatment only
Human metapneumovirus	ü supportive treatment	· Supportive treatment only
Rhinovirus	ü supportive treatment	· Supportive treatment only

How does “provide point of care testing if the result can lead to initiation or modification of a treatment plan” fit with the wide range of possible infectious agents?
There are different schools of thought around screening for a large number of possible causes of respiratory illness. For most point of care tests, I advocate testing based on whether a treatment plan can be initiated or modified based on the result. For respiratory tests in otherwise healthy adults, which excludes people with compromised immune systems, COPD sufferers and those with significant co-morbidities, I believe testing for most of the organisms for which there is no established treatment beyond “supportive treatment” involving fluids, management of aches and fever by over the counter medications has limited value. Most of these illnesses are self-limiting and tend not to result in more serious complications in healthy adults.

The other school of thought would advance the argument that “ruling out” specific sources of infection has diagnostic value. Time and the advancement of testing and treatment methods will determine which approach is right.

Ultimately, the decision of where to draw the line rests with your customer. What approach should you consider in consulting with your customers? Ask to learn, as always. Find out their view and suggest appropriate solutions in collaboration with your most trusted suppliers to meet the diagnostic and patient care need.