Is it COVID? 4 conditions that masquerade as coronavirus

By Naveed Saleh, MD, MS
Published October 6, 2021

Key Takeaways

A strong assessment and plan are rooted in the quality of the differential diagnosis. The proper diagnosis focuses on the use of laboratory tests/imaging, enhances clarity/communication, sheds light on the direction of treatment, improves calls made in prognosis, and can line up preventive options.

Although the concept of a differential diagnosis is key in medicine, physicians vary in their ability to formulate one. Fortunately, doctors can improve this skill. With COVID-19, knowledge is integral to developing a list of differential diagnoses. The following is recent evidence-based information concerning the COVID-19 differentials with respect to four conditions.   

COVID-19 vs interstitial idiopathic pneumonias 

Pneumonia caused by COVID-19 is a dire and trying healthcare emergency. The virus is highly transmissible, detrimental to health, and deadly, taxing healthcare systems worldwide. 

Radiologists and imaging are crucial in the diagnosis of COVID-19. In diagnosing COVID-19 pneumonia, many radiologic findings overlap with those of long-lasting lung diseases. One example involves idiopathic interstitial pneumonias (IIPs). 

“COVID-19 pneumonia differential diagnosis with IIPs is challenging, since these entities may share common radiological findings [such] as ground glass opacities, crazy paving patterns, and consolidations. Multidisciplinary discussion is crucial to reach a final and correct diagnosis,” wrote the authors of a review published in Tomography. 

Of note, IIPs are a diverse group of lung diseases with kaleidoscopic radiological, clinical, and histopathological characteristics.

COVID-19 vs influenza A

Pneumonia secondary to COVID-19 shares pathogenic characteristics with pneumonia caused by influenza A. The two conditions exhibit overlapping symptoms, laboratory findings, and imaging findings.

In a study published in the Journal of Laboratory Analysis, Chinese researchers mined electronic medical records for epidemiological features, clinical features, radiologic findings, and laboratory findings.

The median age of the influenza A patients was greater, and these patients exhibited higher temperatures and more pleural effusion compared with COVID-19 patients. Comparatively, those with COVID exhibited more fatigue, diarrhea, and ground-glass opacity on imaging, as well as higher levels of lymphocytes, red cell counts, absolute lymphocyte counts, and albumin levels, whereas monocyte, C-reactive protein, liver enzymes, and creatinine levels were lower.

On regression analysis, fatigue, ground-glass opacity, and increased levels of albumin were independent risk factors linked to COVID-19 pneumonia, whereas older age, higher temperature, and higher levels of monocytes were independent risk factors tied to influenza A pneumonia.

COVID-19 vs other respiratory disease

Infection with COVID-19 must be rapidly differentiated from other respiratory diseases, including allergic rhinitis, asthma, and COPD. In a study published in the International Journal of Clinical Practice, researchers assessed 522 patients with allergic rhinitis, asthma, and COPD for epidemiologic and clinical features, as well as radiographic findings in COVID-19 patients only. 

They found that COPD and asthma were more frequent in those with COVID-19 compared with allergic rhinitis. Chest CT in COVID-19 patients demonstrated bilateral ground-glass opacity, with fever, dry cough, loss of smell/taste, shortness of breath, diarrhea, and blue lips significantly higher in COVID-19 patients compared with COPD, asthma, and allergic rhinitis.

“The presence of clinical symptoms such as fever, dry cough, diarrhea, loss of sense of smell and taste, shortness of breath, and blue lips in COVID-19 patients, can be used for differential diagnosis between COVID-19 patients and other respiratory diseases,” the authors wrote. “Then, the diagnosis can be confirmed by chest CT scan for COVID-19 patients without the need for a nasopharyngeal swab or PCR test, especially in epidemic countries. Allergic rhinitis patients are the least exposed to COVID-19 infection among other respiratory disease patients.”

COVID-19 ARDS vs ARDS from other causes

Another respiratory condition that needs to be rapidly differentiated in the era of COVID-19 is acute respiratory distress syndrome (ARDS). In a study published in the Annals of the American Thoracic Study, investigators compared epidemiologic and pathophysiologic parameters, biomarkers, and clinical outcomes in a prospective cohort of 27 patients with COVID-19 ARDS vs three historical, pre-COVID-19 cohorts of 14 patients with viral ARDS, 21 patients with bacterial ARDS, and 30 patients with culture-negative pneumonia.

The researchers noted that COVID-19 patients exhibited higher body mass index and were more likely Black or living in skilled nursing facilities compared with the three groups of non-COVID ARDS patients. Furthermore, although COVID-19 ARDS was similar in many ways to other viral causes of COVID-19 ARDS, COVID-19 patients exhibited decreased delivered minute ventilation compared with bacterial and culture-negative ARDS.

Longer dependence on mechanical ventilation marked COVID-19 ARDS compared with the other three arms. “Such detectable differences of COVID-19 do not merit deviation from evidence-based management of ARDS but suggest priorities for clinical research to better characterize and treat this new clinical entity,” wrote the authors.

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