COVID-19, also known as SARS-CoV-2, was declared a pandemic by the World Health Organization (WHO) in March 2020 after Wuhan confirmed its first case in December 2019, thereafter, spreading to over 180 countries by March 2020. COVID-19 is a beta-coronavirus sharing phylogenic similarities to SARS-CoV (1). Sequencing analysis also showed that the COVID-19 virus serology was homologous to a SARS-like coronavirus(2). SARS-CoV is spread by bats, and by extension, COVID-19 is considered to be zoonotic in nature. COVID-19 has emerged as the third novel coronavirus in the last eighteen (18) years (3) and differs from the other coronaviruses in its class due to its longer incubation period and lower fatality rates (2). These novel characteristics have been thought to be the underlying factors in the rapid spread of the disease. A longer incubation time means that infected persons with the disease may have been in contact with many persons even before the onset of COVID-19 related symptoms. This poses a great challenge in the containment of the virus. Measures have been put in place worldwide to help combat the spread of the disease. These measures include washing of the hands, coughing or sneezing into the elbow, and social distancing, which have been fully implemented globally.
Due to the large spread of the virus, research has been launched into the investigation of possible laboratory predictors for COVID-19. Laboratory parameters have been used previously to shed light on the disease severity, defining the prognosis, aid in follow ups, guiding treatment and for therapeutic monitoring (4). Parameters such as interleukin-6 (IL-6), D-Dimer, glucose (GLU), thrombin time (TT), fibrinogen (FIB) and C-reactive protein (CRP) has shown to be indicative of patients being classified as severe or mild with COVID -19 (5, 6). Limited research has been done on the evaluation of the accuracy of laboratory predictors for COVID-19 patients who have been tested positive via RT-PCR.
Patients testing positive for COVID-19 are subjected to a Complete Blood Count (CBC) which serves to guide clinicians in caring for the overall health of patients. Any irregularities point to a series of health issues such as anemia, leukemia and much more. In light of the COVID-19 findings, CBC results were used to show the differentiation between patients who had a severe case of the disease and those that need to be transferred into the Intensive Care Unit (ICU) (7). Patients that had higher blood leukocyte count, > 10*10^9/L, were more likely to have severe COVID-19 and were admitted into ICU.
White blood cells (WBCs) are produced in the bone marrow and serves to fight against infections in the body. COVID-19 patients showed a normal or decrease in WBC and lymphocyte counts at admission into the hospital (8-10). Even though COVID-19 survivors and non-survivors had normal WBCs in Zhao et al., 2020 study, the non-survivors had higher WBC count and slightly reduced lymphocyte counts (10).
Exaggerated elevation of inflammatory cytokines in the body, such as Interleukin-6 (IL-6), causes the onset of a cytokine storm, as seen in COVID-19 patients, which results in multiple organ failure (MOF) and Acute Respiratory Distress Syndrome (ARDS) (9, 11-14). Rapid viral replication in the body causes vigorous pro-inflammatory response causing apoptosis in the lung’s epithelial tissue, leading to hypoxia and ARDS (12, 15).
Studies, such as Zhang L. et al., 2020, reported elevated levels of D-dimer being one of the more common laboratory finding in COVID-19 patients requiring hospitalization (6, 16). D-dimer elevation was associated with a hypercoagulable state of patients, however, its specificity on the main cause of elevation may not be known as D-dimer elevations were associated with several unfavorable events such as occlusion, sepsis, micro-thrombosis, and intravascular coagulation (7, 16, 17).
Lactate Dehydrogenase (LDH) is an enzyme expressed in all cells such as the heart, liver, muscle, kidney, lung and bone marrow (2). During biochemistry laboratory tests, increased LDH levels signaled that there is damage to the cells that it is normally expressed in. Elevated levels of LDH has been associated with worse clinical outcome of COVID-19 patients (7, 18). Monitoring both the LDH and lymphocyte count can differentiate between ICU and non-ICU patients.
Liver damage was reported in SARS-CoV patients which led researchers to investigate the effect of COVID-19 on the liver (19). Several studies reported similar liver abnormalities in COVID-19 patients, both at admission to the hospital and during their hospital stay (6, 19). Elevated levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were reported, ranging from 14% to 53% (9, 19, 20). ALT, AST, Total Bilirubin, Creatinine, and Blood Urea Nitrogen (BUN) were within normal ranges according to Ruoqing Li et al., 2020 (8), however, these results were taken at admission into the hospital as opposed to during hospitalization.
C-Reactive Proteins (CRP) are produced in the liver and studies have shown highly elevated levels in COVID-19 patients which is also a key indicator of MAS (8-10, 13). Higher levels of CRP has been associated with lung lesions and are very important in assessing the severity of the disease in the patient (21). Excessive inflammation was also reflected by very high CRP levels in patients with severe disease state (7).
Laboratory predictors are key components in providing faster and more accurate diagnosis of the novel COVID-19. This is tremendously important due to the rapid transmission of the virus from person to person and it’s long incubation time. Early and accurate diagnosis of COVID-19 can reduce the load on the health care systems worldwide.