How COVID-19 Tends to Present in Laboratory Test Results
Christoph Eberle

How COVID-19 Tends to Present in Laboratory Test Results

Screening and function tests have opened a treasure trove of additional information for disease management and prognosis

Since the start of 2020 the world seems to turn slower. Most of what connects our modern lives has been disrupted. We are adopting new habits forced by a contagion. Within weeks the coronavirus outbreak in Central China turned into a pandemic. There was and still is discussion in some countries around availability of reliable diagnostic testing to confirm individuals suspected of COVID-19 infection. From a public health perspective, having access to these types of tests and performing enough of them across a portion of the general population is viewed as crucial in two ways: to help trace the viral spread and to guide policy makers to gradually lift lockdown restrictions. These RT-PCR-based tests detect the presence of SARS-CoV-2, the novel human coronavirus causing the COVID-19 infection.

While we wait for such a result to confirm the diagnosis, how do other laboratory evidence indicate this infection? Though it presents a new disease to practitioners, its clinical signs are being recorded for future textbooks as the pandemic continues. So are the essential insights that laboratory medicine provides in support of those who care for these patients.  

In April the German Society for Clinical Chemistry and Laboratory Medicine (DGKL) released a compilation of clinical laboratory findings so far observed among COVID-19 infection. These screening and function tests open a treasure trove of additional information for disease management and prognosis. Though this document is intended as professional guidance, even non-professionals curious about pathophysiology will appreciate what can be learned from evaluating body fluids.  Below are listed some of the surrogate markers that are typically changed with COVID-19 infection:


Clinical Chemistry




Lymphocyte count ↓    

D-dimer ↑

LDH ↑   

Eosinophil count ↓


Creatinine ↑, urea ↑




ALT ↑, total bilirubin ↑

High-sensitivity Troponin T ↑



Initially, C-reactive protein (CRP) and lactate dehydrogenase (LDH) as systemic inflammation markers are elevated. Along with low lymphocyte blood counts (lymphopenia) this parameter constellation reflects the acute condition of these patients. Eosinopenia is often found, if lymphocyte numbers are not reduced. Depending on the state and severity of the infection, multiple organs can be affected. Increased levels of alanine aminotransferase (ALT), a liver enzyme, and total bilirubin in blood show hepatocyte damage.

Kidney failure indicated by abnormally high creatine and urea concentrations can present another complication and potentially poor outcome. As the inflection progresses, additional markers are measured during hospitalization and intensive care monitoring.

COVID-19 also may cause heart muscle injury as determined by release of high-sensitivity Troponin T. High serum concentrations of this cardiac-specific structural protein are associated with severe disease progression. Correlating with systemic inflammation from the infection, blood clotting can also be impaired in this state due to activation and consumption of coagulation factors. Among other indicators this is evidenced by the rise of D-dimers, a product from degraded fibrin.

Within the medical profession the understanding of the pathology related to COVID-19 continues to evolve. What is manifesting clinically, leaves biochemical traces laboratory medicine can pick up and follow, as the virus moves through the body. The preliminary information on patterns of COVID-19 laboratory test results mentioned above were collected by Professor Dr. Nicolas von Ahsen, now chief physician at the hospital group Gesundheit Nord in Bremen (Germany). Ten years ago, he was my colleague in the Department of Clinical Chemistry at the University Medical Centre Göttingen in Lower Saxony (Germany). From him I learned what these findings can show and what not, when connected with a real patient’s symptoms. The value added by these measurements now brings back a glimpse of clarity for us, while facing a still unfolding disease.

Today, it is not far for me to drive to one of Charles River’s facilities supporting drug discovery and development. Never in my life was I closer to patients than in my Göttingen years. Today I am not as close, though the mission to improve their lives through my profession has never changed for me.