Which tests make the most sense for diagnosis and follow-up for the COVID patient?
November 2021 – Repertoire Magazine
By Jim Poggi
As we approach what we have come to think of as respiratory infection season, and following last season where the COVID pandemic raged and influenza didn’t show up, there are a lot of questions about what shape this respiratory season will take.
Who is at higher risk of contracting COVID? Is vaccination for COVID working? And how exactly do we define “working”? Will the newest COVID variants, including Delta and Mu, drive higher infection rates? Will flu make its typical annual appearance? Finally, which tests make the most sense for diagnosis and follow-up for the COVID patient? In this column, I will provide information I’ve gathered in my research to shed some light on these issues. At the same time, I will speculate about the respiratory season ahead.
Risk factors
Let’s start with an overview of who is most likely to contract a severe enough COVID infection to require hospitalization, or who may risk becoming a “long hauler.” While I will address the classic risk factors a bit later, there’s now overwhelming evidence that vaccination reduces the chances of becoming seriously ill with COVID or requiring hospitalization. A study by the Virginia Department of Health uncovered some interesting facts.
First, that vaccination is absolutely effective in preventing serious illness. In a study released in August, they reported approximately 170,000 COVID cases in the unvaccinated population compared to about 19,000 among those who were vaccinated. Vaccine effectiveness was considered as “effective” in 80% of adults in the 20-29 age group and rose to greater than 90% in those 60 years of age or older, demonstrating apparently increasing effectiveness with age. A similar study conducted by the county of Los Angeles showed hospitalization rates seven times higher in unvaccinated persons compared to those who were vaccinated.
So, while breakthrough infections do take place among the vaccinated population, vaccine effectiveness is defined as its ability to reduce the incidence or severity of the disease and/or the rate of hospitalization. There is plenty of data out there, and all I have seen supports these conclusions.
Other than vaccination status, what are the other risk factors associated with severe cases of COVID? Classically, a compromised immune system is associated with higher risks of respiratory infection, and that is also true of COVID. In addition, co-morbidities including COPD and other lower respiratory conditions make serious COVID infections and complications from pneumonia more likely. Heart disease, obesity and diabetes are also higher risk factors for COVID and this association seems to hold up for other respiratory infections. Age is also a factor, but is more likely related to the incidence of co-morbidities mentioned earlier than to any other reason.
The CDC reports that the Delta variant of COVID is twice as contagious as previous variants and more likely to cause serious illness. As of mid-September, it was the most common variant of COVID in the United States.
So, while vaccination rates have begun climbing again, the emergence of the Delta variant is likely to continue to drive the infection rate. It’s unlikely that infection rates will match those prior to availability of vaccines, but Delta presents a risk of infection particularly among the unvaccinated and those with other pre-existing health issues.
Forecasting respiratory season
Now to speculate a bit on this year’s respiratory season. Flu incidence remains the wild card. It was virtually absent last year, with few cases reported and the lowest rate of flu tests performed in many years. But, much of the country was in lock down for the typical respiratory season. With the country struggling to open up and return to some semblance of normal at present it seems reasonable to presume that increased social contact will result in more flu cases this year than last. Opinions vary and the season is not yet upon us, but the CDC also cautions that this flu season is likely to be more severe than last.
I believe strep and RSV will also be at higher levels than last year. As of press time, the CDC was reporting the weekly average of COVID cases at 146,182. During the last typical flu season (2018/19) there were more than 37.4 million cases of flu reported.
Which respiratory disease will top the headlines this season is still to be determined. The experienced distributor account manager needs to be alert to the signs of respiratory season incidence in their community and prepared to assist their customers with flu vaccines and tests for flu, strep and RSV as well as COVID. It will be an interesting respiratory season for sure.
How do you prepare?
So, where does testing fit in and how do you prepare? At the top of the season, you need your armamentarium of diagnostic tests to include COVID-specific antigen and antibody tests, as well as RT-PCR for your more sophisticated customers. CBCs are also an important element of diagnosis and monitoring of all the typical respiratory conditions. Monocyte distribution width hematology parameters can signal the development of sepsis and complement IL-6, procalcitonin and lactate.
Some customers will choose CRP as an early screen for an infection and later use more specific tests to identify the infectious agent. Flu, strep and RSV test systems are also critical. Choose from reader based, molecular and traditional lateral flow test options wisely. Each offers differential advantages. Be sure to work closely with your key manufacturing partners to understand the test mix you need and availability of tests since the health care product supply chain has been negatively impacted by COVID.
As customers shift from diagnosis to patient management later in the flu season, the ratio of diagnostic to monitoring tests is likely to shift. It will also be dependent on the underlying co-morbidities of their recovering patients. Diabetics and many obese patients will likely require A1C, glucose and lipid testing along with evaluation of renal function. Patients with underlying cardiac conditions may benefit from BNP and D-Dimer assays also.
Those with underlying immune system issues will need monitoring of their specific condition including HIV, cancer and others. Especially with “long haulers” (typically defined as those whose symptoms persist beyond three weeks), a range of organ tests is useful, again including renal function and general metabolic panels (CMP or BMP). Outside of the lab testing perspective, recovering patients are likely to need pulmonary function tests, cognitive assessments, adjustments of their medications, counseling for depression and other affective issues and in some cases more extensive rehabilitation.
Buckle down and be prepared to be especially busy in the months ahead.