Haematological change can persist for up to 985 Days in Long COVID

Long COVID affects a significant number of people after acute coronavirus disease 2019 (COVID-19), and haematological changes can persist in the COVID-19 phase. 

This study aimed to evaluate these haematological laboratory markers, linking them to clinical findings and long-term outcomes in patients with long COVID.

reference link: https://www.preprints.org/manuscript/202302.0469/v1

Our main findings suggest that the study population had, on average, a positive recovery in the haematological profile, even if symptoms of long COVID were reported for up to 985 days.

Among the 89 hospitalised patients, there were higher mean levels of red/white cells and platelets and percentages of plateletcrit and RDW. In addition, haematimetric parameters, such as MCV, MCH, and MCHC, were higher in shorter periods of long COVID.

Patients presenting with more than six concomitant long COVID symptoms had a higher WBC count, lower PT, and increased PT activity. More than 1 year of long COVID was associated with low haemoglobin levels and increased lymphocyte counts.

Evidence indicates that thrombocytopenia and anaemia influence the severity of acute COVID-19 [7-9], increasing the risk of fatal outcomes. Furthermore, immune throm-bocytopenia was reported 4 weeks after the onset of COVID-19 symptoms, even if limited to 1-week maximum [5].

In contrast, in the present study, patients who were hospitalised during the acute phase of COVID-19, which can characterise a more severe acute involvement, presented with higher levels of haematological markers in the long COVID phase than those who were not hospitalised.

This suggests homeostatic compensation in the convalescence phase after hospital discharge, which is further corroborated by the haematimetric parameters that tend to increase over the months, at least until the first year of long COVID, and with a higher RBC count and RDW percentages in lower periods of long COVID.

In acute COVID-19, leucocytosis and lymphopenia are frequent findings [10,11], making the WBC count indicative of severity, whereas the normalisation of lymphocyte levels suggests convalescence [12-14]. Here, in both worse outcome groups, patients with more than six simultaneous long COVID symptoms, and patients hospitalised in the acute phase, an increase in WBC count was observed, with higher levels mainly of lymphocytes, in addition to increased coagulation activity, when compared with its counter groups.

In the same way that the red series behaved in this study, this increase suggests a response that exacerbates the effects of the acute disturbance emerging in the long COVID phase [6]; however, further investigations are needed.

This study has several limitations. Having additional study groups, such as the con- trol group of patients without long-term symptoms, would allow interesting comparisons regarding the haematological status of patients with long COVID.

Furthermore, assessing the patient’s haematological profile at the time of the COVID-19 acute phase could indicate the course of the haematological implications of long COVID, which was not performed in this study.

However, to our knowledge, this is the first study to provide clues about the haematological condition of patients with prolonged symptoms of COVID-19 long after the acute phase, demonstrating profiles of important markers in determining the severity of the involvement of SARS-CoV-2 within up to 985 days prior to the onset of symptoms.

Analysing recognisably impactful severity-predictor markers of COVID-19 in post-acute scenarios is extremely important to identify possible long-term changes in the haematological system.

Therefore, observing abnormalities in screening markers, such as those investigated here, is an important strategy to identify more severe haematological diseases in the future, long after the acute SARS-CoV-2 infection.

Moreover, relating the profile of these markers to clinical outcomes in patients with long COVID provides a gen- eral overview for future studies that aim to build a risk stratification for patients with several months of long COVID.