key: cord-0983856-uazvenmu
authors: Letícia de Oliveira Toledo, Sílvia; Sousa Nogueira, Leilismara; das Graças Carvalho, Maria; Romana Alves Rios, Danyelle; de Barros Pinheiro, Melina
title: COVID-19: review and hematologic impact
date: 2020-07-11
journal: Clin Chim Acta
DOI: 10.1016/j.cca.2020.07.016
sha: 9a8026bd730e725cc3ad950b06aa27d0960e75e7
doc_id: 983856
cord_uid: uazvenmu

Abstract In the last decades, coronaviruses have been a major threat to public health worldwide. SARS-CoV-2 is the third known coronavirus that causes fatal respiratory diseases in humans. The initial clinical features of SARS-CoV-2 infection are quite nonspecific and not all suspected patients can be tested to exclude or confirm the diagnosis. Increasing scientific evidence has shown that abnormalities in routine laboratory tests, particularly hematological tests, have the potential to indicate, in a quick, practical and economical way, the need for specific laboratory tests for the diagnosis of SARS-CoV-2 infection, besides assisting in the prognosis of the disease and in the optimization of its clinical monitoring. In order to address in a simple and practical way the various aspects related to SARS-CoV-2 infection, this review reports the history of the virus, the epidemiology and pathophysiology of COVID-19, with emphasis on its laboratory diagnosis, particularly in hematological changes found during the course of the disease.

of unknown etiology, epidemiologically related to a local wholesale market for wildlife and seafood [8] . After laboratory investigations, on January 7, 2020, the causative agent of these infections was identified, considered a new CoV in 2019 and officially designated by the World Health Organization (WHO) as 2019-nCoV [9] . Subsequently, the International Virus Taxonomy Committee renamed 2019-nCoV as SARS-CoV-2 [10, 11] .

SARS-CoV-2 was quickly transmitted among humans, spreading to different countries around the world, threatening human life and generating many financial losses [4] . On January 30, 2020, WHO issued a worldwide public health alert regarding the emergence of a new epidemic viral disease [12] . On February 11, 2020 , WHO announced the name for the epidemic disease caused by SARS-CoV-2: coronavirus disease 2019 and declared, on March 11, 2020, a pandemic state [13] .

SARS-CoV-2 spread occurs by inhalation or ingestion of viral droplets. Thus, the main sources of human infection are contact with any contaminated surfaces (viral droplets can spread from one to two meters and settle on surfaces) [14] or with the respiratory droplets of infected people (e.g. through sneezing, coughing or physical contact). SARS-CoV-2 infection can also occur by touching the nose, eyes or mouth with hands contaminated with the virus [15] . A recent study identified high SARS-CoV-2 RNA concentration in aerosols present in bathroom areas of patients at two hospitals in Wuhan, dedicated to COVID-19 cases, and in public areas prone to agglomeration, raising the concern to evaluate the potential of transmission of this virus by aerosols [16] . Therefore, the correct hand hygiene, use of personal protective equipments and social isolation are very important strategies in combating the transmission of SARS-CoV-2 [15] .

Quarantine measures should be established to restrict the movement of uninfected people in regions where there is an epidemic outbreak and infected people, who can act as spreading the virus agents as long as the symptoms last until clinical recovery [14] .

Currently, there is no proven antiviral treatment for COVID-19 [15] and knowledge about SARS-CoV-2 is still scarce. Daily, reported cases and deaths number increase considerably in numerous regions of the planet. In this context, early diagnosis and infections prevention has become one of the priorities for the control of this coronaviruses [17] . SARS-CoV-2 incubation period is up to two weeks, usually ranging from three to seven days after infection. In most cases, SARS-CoV-2 infection is asymptomatic and, in that case, the individual will not need medical assistance (up to 80%). However, asymptomatic patients are an important source of spread of CoV, who, as they continue with their normal daily activities, can spread the virus to those in contact [10, 18] .

In symptomatic cases, symptoms of COVID-19 are nonspecific [15] and the clinical presentation is similar to SARS-CoV infection. The most commonly reported symptoms are fever [19] , dry cough, dyspnoea and fatigue [15, 17] . Nonrespiratory symptoms (e.g. diarrhea, nausea, vomiting, headache and muscle pain) are usually uncommon [17] .

It is known that in some people the infection can get worse, requiring hospitalization and even referral to the intensive care unit (ICU) [10, 20] . In these cases, COVID-19 may progress to acute respiratory distress syndrome, followed by septic shock, refractory metabolic acidosis, coagulation dysfunction, multiple organ failure and, consequently, death [15] .

SARS-CoV-2 can cause serious clinical complications, especially in elderly patients and in those with previous comorbidities, especially diabetes [20] ; cardio and cerebrovascular diseases [21, 22] ; obesity; cancer and digestive, endocrine, nervous and respiratory systems pathologies [23] , constituting 50% to 75% of deaths [14] . Porcheddu et al. (2020) , when comparing mortality rates of SARS-CoV-2 patients in China and Italy, they realized that in China most deaths occurred in the age group above 50 years, while in Italy over 60 and in both countries, comorbidities have been shown to be important contributors to death [24] .

For COVID-19 laboratory diagnosis, to date (July/2020), tests used are based on the following methods: real-time reverse transcription-polymerase chain reaction (RT-PCR); serologic tests for SARS-CoV-2 (Anti-SARS-CoV-2

IgA, IgM and/or IgG), utilizing ELISA, chemiluminescence or immunochromatography assays; in addition to SARS-CoV-2 antigen immunochromatographic test in upper respiratory tract specimens [25] [26] [27] .

The RT-PCR is the gold standard for SARS-CoV-2 detection and it is the laboratory test of choice for the diagnosis of symptomatic patients in the acute phase [28] . [32] .

The serological method is mainly adopted for retrospective diagnosis and its sensitivity is generally lower than that of the molecular method. Serological tests are based on the detection of the specific antibody (IgA, IgM and IgG) produced against SARS-CoV-2 or the antigen of the vírus [31] . Serology can be performed when the availability of molecular tests is limited or if there are at least 14 days after the onset of symptoms [30] . Less than 50% of patients with COVID-19 have detectable antibodies in the serum before 7 to 10 days after the onset of symptoms [33] .

As the identification of SARS-CoV-2 infection has become a major challenge in clinical practice, for social, financial, logistical and analytical reasons, the search for abnormalities in routine, low-cost and suggestive (or pathognomonic) laboratory parameters is extremely important to assist in confirming COVID-19

diagnosis. In this context, we performed the present literature review on hematological and biochemical changes in SARS-CoV-2 infection, whose knowledge by health professionals could be useful in the management of the disease.

It is known that in SARS-CoV-2 virus infections, as well as in other infectious diseases such as influenza [34] , varicella [35, 36] , dengue [37] [38] [39] , acquired human immunodeficiency virus (HIV) [40, 41] , SARS-CoV [42] [43] [44] [45] and MERS-CoV [46] , hematological changes can occur and often present, the potential to optimize the monitoring of infectious process or to indicate the suspicion of their severity.

Laboratory abnormalities, particularly hematological changes, allow checking the status of SARS-CoV-2 infection, since the hematopoietic system and hemostasis suffer significant impacts during the evolution of COVID-19 [47] .

The most common hematological findings include lymphocytopenia [19, [48] [49] [50] , neutrophilia [23, 51, 52] , eosinopenia [50, 53, 54] , mild thrombocytopenia [50] and, less frequently, thrombocytosis [48, 55] . The presence of reactive lymphocytes has been reported only occasionally [56] . The leukocyte count may be normal, reduced [19, 50, 57] or increased [22, 23, 58] . According to a metaanalysis [59] , leukocytosis, lymphopenia and thrombocytopenia are associated with greater severity and even fatality in COVID-19 cases. Main laboratory changes in patients with an unfavorable evolution of SARS-CoV-2 infection are shown in Figure 1 .

As already reviewed by Terpos et al. [60] , such abnormalities have been reported by several authors and are associated, in different parts of the world, the need for ICU admission and SARS development. Still according to these authors, during the first days of the disease, when patients manifest non-specific symptoms, the leukocyte count and the absolute value of lymphocytes are normal or slightly reduced. Posteriorly, around the 7th to the 14th day of infection, the disease begins to affect organs with greater SARS-CoV-2 cell receptor expression, the angiotensin-converting enzyme 2 (ACE2) [61] , such as the lungs, heart and gastrointestinal tract, with characteristic clinical symptoms and expressive increase in the levels of inflammatory mediators and cytokines [9] . At this disease stage, more expressive hematological changes are highlighted, particularly a significant reduction in the lymphocytes number. This finding was more evident in those who suffered death compared to those who survived. The latter showed their nadir for lymphocytopenia around the 7th day of symptoms, with subsequent recovery [22] .

Thus, on the basis of Terpos et al. [60] , it is possible to admit that the dynamics of the absolute lymphocyte count, that is, its serial count may be predictive of the clinical outcome of patient. An analysis of the literature revealed that among all the hematological abnormalities, lymphocytopenia has been highlighted as the most frequent since admission to death [19, [62] [63] [64] [65] [66] [67] . From data based on the complete blood count, it is possible to calculate ratios between its parameters, whose interpretation has considerable clinical value. Thus, a decreased lymphocyte/leukocyte count ratio has already been reported indicating severe disease and/or fatal outcomes [65, 68] . Similarly, increased neutrophil/lymphocyte and neutrophil/platelets ratio may be indicative of myocardial injury and increased mortality [69] . Therefore, it is important to monitor the hematological parameters in order to try to assess the progression and prognosis of COVID-19.

According Terpos et al. [60] , Regarding the lymphocytes morphological aspect, as reported by Fan et al. [56] and Chng et al. [70] , in most patients with low lymphocyte count, these were shown to be reactive with lymphoplasmocytoid characteristics. In addition to the lymphocytes morphological abnormalities, Zini et al. [71] , In a retrospective study of 183 patients with COVID-19 [76] , prothrombin time, D-dimer and the degradation products of fibrin/fibrinogen, measured at hospital admission, were higher in non-surviving patients than in survivors, respectively.

In those hospitalized late, antithrombin activity (AT) and fibrinogen levels were significantly lower in non-survivors, suggesting that conventional blood coagulation parameters during the course of the disease may be associated with prognosis.

Most of the patients who died had diagnostic criteria for disseminated intravascular coagulation (DIC). Lippi e Plebani [77] stressed that the evaluation of the hemostatic system by specific tests should integrate the routine clinical monitoring of the patient with COVID-19, in view of fulfillment of the laboratory criteria for the diagnosis of DIC in nearly three quarters of patients who died.

Other laboratory abnormalities included increased erythrocyte sedimentation rate (ESR), increased levels of lactic dehydrogenase (LDH), C-reactive protein (CRP) and muscle enzymes, in addition to changes in cardiac, renal and liver functions, among others [75] .

The following is a summary of some main studies carried out with emphasis on the description of laboratory data obtained.

Huang et al. [57] , in a study in Wuhan, China, reported the epidemiological, were found by Liu et al. [79] , who reported that the severity of COVID-19 can be predicted by lymphopenia, neutrophilia, hypoalbuminemia, high levels of LDH and CRP. In addition, when compared to healthy controls, plasma levels of angiotensin II in patients infected with SARS-CoV-2 were significantly higher and strongly associated with lung injury and viral load. According Jin et al. [75] , it is necessary to pay close attention to patient with an absolute lymphocyte value less than 0.8×10 9 /L or a significant reduction in the number of CD4 and CD8 T cells, being recommend to evaluate the hematological alterations again after three days. Main laboratory changes, especially hematological ones, related to the diagnosis and/or prognosis of SARS-CoV infection are shown in Table 1 .

Guan et al. [19] kinase (CK), D-dimer, prothrombin time, creatinine, IL-6 and procalcitonin, whose parameters were shown to be associated with hospital death. D-dimer levels above 1 µg/mL at admission were associated with a greater chance of death.

Lymphocyte count was significantly higher in surviving patients than in non survivors. It is noteworthy that in survivors, the lymphocyte count was lower on the 7th day after onset of the disease and improved during hospitalization, while severe lymphopenia was observed until death in non survivors. D-dimer levels, high sensitivity cardiac troponin I, LDH, IL-6 and ferritin were higher in non survivors compared to survivors and increased with disease progression. Thus, the levels of D-Dimer and highly sensitive cardiac troponin may indicate a greater or lesser risk of death for patients with SARS-CoV-2 infection [80] . Furthermore, lymphopenia seems to be one of the most relevant hematological abnormalities in COVID-19, its use being suggested as a severity biomarker of this infection [81] .

For both groups, survivors and non survivors, LDH increased at the beginning of COVID-19, but decreased from day 13 in those who survived. Lippi and

Plebani [77] stated that on hospital admission of patients with SARS-CoV-2 infection, procalcitonin does not appear to be significantly altered, however, its progressive increase may suggest a worse prognosis. They have also suggested that the measurement of other biomarkers, such as presepsin, would probably help to increase the accuracy in the identification of serious cases of COVID-19

and would improve the current approach to predict the risk of mortality. Wang et al. [58] conducted a retrospective study with hospitalized patients with SARS-CoV-2 infection (N=138) at Zhongnan Hospital, Wuhan University, China. When comparing the laboratory characteristics of patients admitted to ICU with those not admitted, several significant differences were identified, such as a higher leukocyte and neutrophil count, and elevated levels of D-Dimer, CK, urea, creatinine, hypersensitive troponin I, procalcitonin, LDH, AST, ALT and total bilirubin in the first group. In addition, it was found that during hospitalization, most patients had marked lymphopenia and in non survivors lymphopenia worsened over time. Leukocyte and neutrophil counts, and D-Dimer levels were higher in non survivors than in survivors, findings similar to those identified by Zhou el al. [22] . With COVID-19 evolution and the worsening of clinical condition, the urea and creatinine levels increased progressively until death. These changes suggest, according to the researchers, that SARS-CoV-2 infection may be related to coagulation activation, cellular immune deficiency, and myocardium, liver and kidneys lesions.

Regarding the platelet changes observed during the course of COVID-19, a possible mechanism for abnormal thrombopoiesis related to SARS-CoV-2 infection has been proposed by Yang et al. [45] . According to these researchers, We believe that a tool with such characteristics would have a potential value in clinical practice, considering its efficiency, the ease and speed in obtaining laboratory data, in addition to its low cost.

Finally, in the light of reports in the literature about the importance of the blood group in the clinical manifestations of COVID-19 [85] , we also suggest that the ABO blood group be incorporated into the variety of tests requested. This recommendation is based on studies by Ellinghaus et al., 2020 [85] , whose authors have reported the involvement of ABO blood groups in susceptibility to COVID-19. According to the same authors, blood group "O" is associated with a lower risk of infection by SARS-CoV-2 compared to non O blood groups, while blood group A was associated with a greater risk than those non A.

Since Furthermore, this review focused on studies practically from the same region, due to the fact that the first patients diagnosed with SARS-CoV-2 infection were in

China.

Finally, still in the laboratory context, it is essential that good clinical laboratory and biosafety practices prevail and that the patient be the center of attention. Additional training of laboratory personnel responsible for collecting, transporting and handling biological samples and carrying out the various laboratory tests for patients with COVID-19 is recommended. Training for new demands and development of skills in data interpretation are also required, as well as cooperation and collaboration among laboratory professionals. In today's challenging times, more than ever, the clinical laboratory needs to be patientcentered and with qualified leadership to be safe, efficient, effective and timely.

This study was financed in part by the Coordenação de Aperfeiçoamento 

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Table 1. Main laboratory changes related to diagnosis and/or prognosis of SARS-CoV infection

Figure 1. Main laboratory changes in patients with an unfavorable evolution of SARS-CoV-2 infection