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On the Clinical Diagnosis of COVID-19

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In Director's Blog, I previously wrote about excessive testing, including unnecessary CT scans and EEGs in the diagnosis of autism or attention deficit hyperactivity disorder (ADHD). This was meant to explain that there are times when the diagnosis of an illness or disability is not made with particular testing, but rather based on the clinical manifestations and course of the disease.

At present, many people are concerned about the diagnosis of COVID-19, and PCR testing has become a topic of much discussion. As you know, PCR testing is currently considered to be essential in the diagnosis of COVID-19.

As a pediatrician, I have seen many children who had the measles, flu, or a common viral infection like herpangina. Through examination and testing, I make a diagnosis regarding the type of virus and then provide treatment. So, in most cases, how is the diagnosis of viral infection conducted?

The most rigorous methods for diagnosing viral infection involve using samples from the patient (blood, a throat swab, cerebrospinal fluid, etc.), cultivating and enabling proliferation of the virus. Then the specific antibody that binds (or reacts) to the proliferated virus is identified to confirm the type of the virus. However, in most cases, this method will require several days or more for the virus to multiply. This is where the PCR method comes in--using a special kind of enzyme, it increases the DNA or some of the RNA of the virus approximately 10 million times, which enables identification of the virus with the above-mentioned methods. The PCR method shortens the time it takes the virus to proliferate by several hours, which can then be used in the diagnosis of COVID-19 infection in the above manner.

So, how is viral infection, which occurs in children every day, diagnosed at the site of the clinical examination? Among the many viral infectious diseases that afflict children are herpangina, pool fever, chicken pox, influenza, rubella, the mumps, erythema infectiosum (fifth disease), hand, foot and mouth disease, RS virus, rotavirus, and the herpes virus.

In the diagnosis of these common viral infectious diseases, PCR testing is not used, although it is, of course, possible. In the case of chicken pox with the typical symptoms of a rash, erythema infectiosum, hand, foot and mouth disease, intraoral observations (herpangina, etc.), and other observations (parotid swelling→mumps, etc.), it is a common practice to make a diagnosis based on clinical observation and skip viral testing.

In cases of influenza, where the patient's condition becomes serious at times, the symptoms are hard to distinguish from a common cold. In such cases, a rapid diagnosis can be easily made in ten minutes with a swab of the patient's throat and mucous membranes, using a reagent that responds to the constituents of influenza virus. This is called the antigen testing. In the case of low influenza virus levels, the test results will come back negative, which means that tests conducted prior to symptoms such as fever will produce negative results and not lead to a correct diagnosis.

If you catch influenza, there are medicines such as Tamiflu, Inavir, Xofluza, so it is possible to reduce symptoms if you are diagnosed early and these medicines are prescribed.

Such rapid testing methods have been developed quickly in recent years, not only for influenza, but also for the rotavirus, norovirus, Adenoviruses, and Respiratory Syncytial Virus (RSV).

But what is done in the case of a viral infection other than influenza, when it is necessary to make a definite diagnosis based on the patient's condition and the severity of the symptoms? When immediate results are desired and a PCR test is possible, this test is conducted to detect the virus, but in most cases, treatment is given based on clinical diagnosis. If a definitive diagnosis is desired, it is given somewhat later by antibody testing.

At present, PCR testing is the principle method used in a definitive diagnosis of COVID-19, and antigen testing, which is a kind of rapid testing such as those for influenza, has already been developed, so they may become the main practices in the future.

Many people may think that PCR testing is necessary to diagnose COVID-19, but in fact, in the actual treatment of COVID-19, doctors do make a clinical diagnosis without PCR testing.

I have introduced some research on the situation regarding COVID-19 and children in Wuhan, China on this website. A considerable of number of children have been diagnosed without PCR testing. If they live in an endemic area and a parent is confirmed to have COVID-19, the child is checked for fever and pneumonia (CT scan), and if other infections can be ruled out based on the clinical condition, the child is then counted as infected by COVID-19.

Recently, a Japanese doctor who now works in New York made public some notes that he took when he tested positive for COVID-191). After his infection was confirmed by PCR, a family member developed a fever and he asked the medical facility to provide PCR testing, but he was told that family members of patients had a 100% probability of testing positive, so there was no reason to do so. In other words, in that situation, diagnosis is made according to the clinical manifestation. The symptoms of COVID-19 cannot be distinguished from those of a cold, for instance, fever, coughing, and fatigue, so PCR testing has become very important. However, based on what we now know about the loss of sense of smell and taste or characteristic CT and MRI observations of the lungs, it is possible that diagnosis without PCR testing will become common practice in Japan as well.


  • 1) "COVID-19 ni rikan shita ishi no shogen" [Testimony of a physician infected with COVID-19]. Nikkei Medical. May 2020, p. 24-27.
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sakakihara_2013.jpg Yoichi Sakakihara
M.D., Ph.D., Professor Emeritus, Ochanomizu University; Director of Child Research Net, Executive Advisor of Benesse Educational Research and Development Institute (BERD), President of Japanese Society of Child Science. Specializes in pediatric neurology, developmental neurology, in particular, treatment of Attention Deficit Hyperactivity Disorder (ADHD), Asperger's syndrome and other developmental disorders, and neuroscience. Born in 1951. Graduated from the Faculty of Medicine, the University of Tokyo in 1976 and taught as an instructor in the Department of the Pediatrics before working with Ochanomizu University.
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