by 
Nonspecific findings and symptoms can be caused by a variety of health conditions, so the puzzle of finding their origins can leave people sick but undiagnosed for years or even a lifetime. The existence of nonspecific findings and symptoms highlights the importance of research that advances the ability to diagnose illness quickly and accurately.
A “nonspecific finding” is something like a low red blood cell count. It can be observed by a clinician in bloodwork performed at a routine visit or in emergency cases. However, merely being observed doesn’t mean the cause is immediately known. A patient may be pre-symptomatic (not showing symptoms) or having symptoms that are nonspecific. A “nonspecific symptom” is something that is reported by a patient but cannot be observed. Nonspecific symptoms may include chronic fatigue or pain that is not related to a known injury.
For all its complexity, the body has only so many ways to show injury and so many ways to combat disease. The combination of injury by a pathogen and the host response can generate a typical picture that makes up a case. Every disease has a description of what makes up the most common case, but because people are diverse this description may not always fit the symptoms that are reported within a population. A person’s genetic makeup, immune status, and general health can affect their response to a certain pathogen, especially one that is novel to humans.
For example, the CDC is continually updating the most common symptoms of COVID-19, the disease caused by SARS-CoV-2. The current CDC common symptoms list used to be shorter, but symptoms such as loss of smell and taste have been added as they have been noted in some cases. The CDC also points out, “This list is not all inclusive.”
How Do Scientists and Clinicians Track This Growing List of Symptoms?
The International Statistical Classification of Diseases and Related Health Problems codes (ICD codes) have been developed by the World Health Organization (WHO) to better communicate about the prevalence of disease. Diseases and health conditions have ICD-10 codes related to them. If you visit a hospital or medical center and are diagnosed with a disease, the matching code will most likely be entered into your medical record. In the US, these codes determine insurance billing. Non-specific findings and symptoms have ICD-10 codes R00-R99: “symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified.”
WHO is continually updating these codes. Code U07.1 was developed for a confirmed COVID-19 diagnosis. Code U07.2 was developed for a clinically-epidemiologically, probable or suspected case of COVID-19. Clinicians have been directed by WHO to also enter codes for symptoms. This will help collect statistical information about what symptoms are seen with COVID-19.
The reason for including symptom codes is that other less common symptoms that might be caused by SARS-CoV-2 can be puzzling. Examples include rash, acute hepatitis, and diarrhea. But even with a signature symptom, a diagnosis isn’t immediately obvious. The most common symptom of COVID-19, cough, is shared with a variety of illnesses caused by pathogens, environmental pollutants, cancer, kidney failure and more. Nonspecific findings and symptoms can be difficult to diagnose, leaving physicians and patients frustrated.
We have written about the importance of laboratory pathogen testing, particularly PCR testing that identifies the presence of particular pathogens that may cause disease. But sometimes people go years without diagnosis. People who didn’t have a chance to be tested for COVID-19 may experience effects of their illness without the cause ever being firmly identified. This experience is well understood by patients with diseases that are difficult to diagnose, such as vector-borne diseases like bartonellosis and Lyme disease.
The frustration of living with nonspecific signs and symptoms is why we are motivated to continually improve diagnostic capabilities in vector-borne disease. We see the same dedication in our colleagues working on SARS-CoV-2 testing. As the saying goes, “The kindest form of medical care is an accurate diagnosis.”
References
Otto, M. A. (2020). Skin manifestations are emerging in the coronavirus pandemic. The Hospitalist. Available at: https://www.the-hospitalist.org/hospitalist/article/220183/coronavirus-updates/skin-manifestations-are-emerging-coronavirus-pandemic
Pan, L. et al. (2020). Clinical characteristics of COVID-19 patients with digestive symptoms in Hubei, China: A descriptive, cross-sectional, multicenter study [online pre-print version]. American Journal of Gastroenterology. Available at: https://journals.lww.com/ajg/Documents/COVID_Digestive_Symptoms_AJG_Preproof.pdf
Wander, P. et al. (2020). COVID-19 presenting as acute hepatitis [online pre-print version]. American Journal of Gastroenterology. Available at: https://journals.lww.com/ajg/Documents/COVID19_Bernstein_et_al_AJG_Preproof.pdf
World Health Organization. (2020). COVID-19 coding in ICD-10. Available at: https://www.who.int/classifications/icd/COVID-19-coding-icd10.pdf?ua=1