Diagnosing silent infections before they turn serious.
By Jim Poggi
We all recognize the seriousness of infections we see right before us like influenza, strep, other respiratory and skin infections. While these acute infections are easy to identify – and for the most part self-limiting or easily treated – even the most obvious infections can lead to severe morbidity and long-term complications.
In addition, our customers recognize the differences in treatment programs posed by bacterial rather than viral infections. It is widely recognized that even these common seasonal infections can bring serious complications. While influenza is viral and antibacterials have no effect on it, group A strep is bacterial and can be effectively treated with antibacterials. Untreated group A strep respiratory infections can also lead to rheumatic fever and even rheumatic heart disease. Group A strep can also proceed to become invasive leading to very serious complications including streptococcal toxic shock syndrome and flesh-eating disease (necrotizing fasciitis). Influenza infections particularly in the elder population can lead to pneumonia and death.
So, what’s my point? In this column I plan to explore initial diagnoses of the obvious infections we usually think of, consider careful follow up of these infections to avoid serious complications, and then discuss the next level of “silent infections,” ones that usually remain asymptomatic until they become very serious. As valued consultants to our customers, we need to stay on top of the issues they encounter daily, and infectious diseases, obvious or occult (not obvious) are a part of their daily lives. Let’s come up to speed on these infections and the diagnostic tools we offer.
What we already know
The following are statistics on easy-to-identify infections:
- Influenza. There were 38 million cases of influenza reported to the Centers for Disease Control and Prevention (CDC) in 2019 resulting in 18 million healthcare visits, 405,000 hospitalization and 22,000 deaths.
- Strep. In that same time frame, strep resulted in over 5.2 million outpatient visits. Invasive strep with the most serious risk of complications resulted in an estimated 10,000 deaths annually and the incidence of invasive strep is rising.
- RSV. These infections lead to about 120,000 hospitalizations annually, equally divided between children under five and adults over 65.
What “silent infections” are out there?
We need to be aware of the dangers of “silent infections,” diseases that are infectious, spread quietly and quickly from one person to another with limited symptoms. From casual contact in large public gatherings to intimate contact between sexual partners there is a substantial list of infections we often think of as isolated, and not necessarily part of the big picture of infectious disease. But they are out there, and they create a serious risk to the public health daily.
What is the incidence of “silent infections” in the U.S.?
In 2019, the most recent year for which I have data, other infectious diseases accounted for 10.2 million physician office visits, 4.7 million hospital visits and 790,000 deaths. Given that there are about 230,000 primary care physicians, this data means they are seeing an average of one patient with a non-respiratory infection each week. And remember, many of these infections present without obvious symptoms.
Quick quiz: name the top five infectious non-respiratory diseases in the U.S. As an added bonus, name the next three (at least one was a big surprise to me). The top five in order are chlamydia, gonorrhea, syphilis, salmonellosis, and Lyme disease.
Some data sources also list E. coli, staph, herpes and norovirus in the top 10. The top five non-respiratory infectious diseases cause over 2.6 million cases annually and the incidence is growing. The next three infectious diseases: hepatitis A, pertussis (whooping cough) and tuberculosis.
As we think about the challenges our customers experience, many of these infections, not including the GI disorders, present with few symptoms. We are all familiar with our respiratory tests and we know that they are critical to our customer diagnostic programs in the fall and winter.
But what do we offer for the “silent” infections? First, for diagnosis of silent infections to occur, there needs to be a trusting relationship between the patient and the care giver and, in some cases, careful history and physical, asking the right questions about lifestyle and carefully looking for signs of skin lesions and jaundice. Beyond that, lab tests become the fundamental tools to establish the initial diagnosis and to follow up post treatment to assure a return to health.
Which screening lab tests are we talking about here?
From a perspective of screening for an infection if the history and vital signs (physical exam) indicates a need, there are several pathways to take. C-reactive protein can confirm the presence of an infection but is non-specific and not often used as a first line screen. Some CRP tests are CLIA waived.
Another diagnostic consideration, more often used in hospitals than primary care practices, is erythrocyte sedimentation rate (ESR). This also indicates an infection but has the same drawback as CRP; it is not specific and leads to one or more additional tests to confirm the infection and work to pinpoint its source. Some ESR tests are also CLIA waived.
For first-line determination of an infection and subsequent determination of whether it is viral or bacterial in nature, you cannot beat the complete blood count (CBC). While most CBC tests are CLIA moderate complexity, the type and amount of data they provide makes the CBC the first choice when laboratories are trying to identify an infection. Elevated white count is an immediate red flag indicating the presence of an infection.
In addition, the white blood cell differential (WBC diff) takes this information to the next level, and can point to a bacterial or viral source of the infection. Typically, an increase in neutrophils, the most common WBCs, indicates a bacterial infection. An increase in lymphocytes more often points to a viral infection. An increase in eosinophils can point to an allergy and lead to a different path to diagnosis.
While infections can be complicated, the CBC is not. In a minute or less the lab receives at least 11 different parameters that can point to general health concerns (hemoglobin and hematocrit are examples that may indicate anemia or a bleeding disorder) or an infection, with the WBC differential well established as the gold standard for initial screen for an infection. Just as important, once a treatment program has begun, follow up with a CBC can demonstrate the effectiveness of the treatment.
Which lab tests make sense to identify a “silent infection”?
This is where things get complicated and the skills of the clinician in drawing out information of the patient come into play. Respiratory infections and most staph infections are readily diagnosed during the vital signs exam. But, there is an increasing incidence of sexually transmitted illnesses (STIs) and while the conversation between the clinician and the patient can become somewhat awkward, it is important for the clinician to understand the recent (and in the case of syphilis) past history of the patient’s sexual behavior.
It is in the best interests of the clinician, the patient, their close contacts and ultimately the healthcare system to have an open, candid discussion to help rule out one of the major causes of STIs. If the clinician has a concern that the patient may be harboring an STI, there are several excellent choices, some of them waived, for STI assays.
Be sure to stay in close contact with your key lab manufacturers who can provide you with information regarding the STI assays they have available and their CLIA status. They can also help you develop conversational cues to make your discussion with your key customers productive, rather than uncomfortable. In my experience, many clinicians, particularly those with stable patient populations in more affluent areas, believe STIs “can’t or don’t happen here.” The data indicates otherwise, and it is in the best interests of the experienced distribution account manager to offer the full range of testing possibilities, from initial diagnosis of infection to definitive diagnosis options.
My research has uncovered information indicating that over 33,000 curable STIs are contracted in the U.S. daily. More surprisingly to me, the CDC reports that there are 68 million Americans with an STI. That’s 1 in 5 Americans. Think it can’t happen here? Think again. Both syphilis and tuberculosis are increasing in incidence. Your trusted lab manufacturer should be able to provide you with data and talking points to help your customers understand that it can happen here. In the case of tuberculosis, the broad range of medications that deliberately lower immune response to help treat arthritis and other autoimmune diseases is often associated with this increase in incidence.
Careful vital signs examination along with history questions focused on whether the patient has traveled to an area where tuberculosis is more common or whether they are taking a newer arthritis medication would be critical to early diagnosis of tuberculosis. There are numerous new TB assays available, most of them are molecular. Your trusted lab manufacturer is the best source of information about assay choices and ways to open up the discussion with your customers. TB is another classic “does not happen here” disease, but changes in available medications are also part of the big picture regarding the increase in incidence of TB in the general population.
What’s the bottom line?
In addition to obvious respiratory and skin infections, I have provided you a list and some food for thought regarding the next level of more difficult to identify infections. As you can see from the data, there are a lot of patient visits for these less obvious sources of infection.
I have also reinforced the outstanding value of the CBC in getting to the heart of the matter: does the patient have an infection? If so, is it viral or bacterial? That answer clarifies the decision to administer antibiotics and helps with antibiotic stewardship, an initiative we all get value from. I hope I have given you a bit of insight on the less obvious “silent infections” and how to work with your trusted lab manufacturers to deliver the story.
In my experience, even a polished rookie can tell the respiratory testing story effectively. The proof of a well-established and well-respected lab consultant is just how far you can take the discussions on infections and the solutions you have to offer. The best lab consultant can discuss the “silent infections” nearly as easily as they can respiratory infections. I am confident that, with the help of your trusted lab manufacturers, you can increase your skills and add additional customer value to your list of credentials.