Discussion
Previously, many symptoms such as fatigue, respiratory dysfunction, exercise intolerance, psychiatric disturbances, and weakness had been experienced by studied patients after the severe acute respiratory syndrome (SARS) attack in 2003.[ 6,7] A meta‐analysis of 28 longitudinal studies reported that 25% of SARS and Middle East respiratory syndrome coronavirus infected patients had reduced lung function and exercise capacity at 6 months following discharge from the hospital.[8]
A review of available evidence on patients with COVID-19 infection suggested that post-acute COVID-19 recovery may be not complete. This evidence indicates that even those classified as mild infection continue to have persistent symptoms that overlap considerably with those recovering from more severe infection. However, the natural history, prevalence, causes, and predictors of these symptoms remain obscure.[3]
Descriptive clinical follow-up study of 150 patients showed that two thirds of adults with noncritical COVID-19 had complaints, in particular smell disturbances, shortness of breath or asthenia, up to 60 day after symptoms onset.[2]Aa recent study from Italy has found that about 87% patients who were discharged from the hospital after recovery from COVID-19 showed persistent symptoms , particularly shortness of breath and fatigue.[9] Persistent shortness of breath and cough may be attributed to pulmonary cellular damage and increased cough reflex sensitivity. Whether there is cardiac contribution to post-acute persistent symptoms requires further interrogation. [10]
The association of high Hb at presentation with persistent fatigue and high PMV with complete recovery in our study deserve appropriate consideration. The nucleic acid of coronavirus might be closely related to abnormal hemoglobin metabolism in humans. The coronavirus attacked the beta chain of hemoglobin leading to toxic and inflammatory state in the tissues. Heme linked sites of coronavirus protein may be relevant to the high infectivity related to the virus replication Thus, the higher the hemoglobin level, the higher the risk of covid-19 disease infection and burden.[11]
In patients with chronic fatigue syndrome, it has been reported that RBC are larger and less deformable than those of healthy control leading to impaired microvascular perfusion and tissue oxygenation. [12].
Of note, MVP, as a marker of variation in platelet size and age, is reported to be a potential indicator of platelet function and activation.[13] increased MPV may suggest that these platelets may present in hyperactive state. Higher platelet turnover is associated with considerable change in platelets size and release of young platelets, which are functionally more active and have higher volumes than older platelets. Given this association high PMV with increased production of young and active platelets, It can speculated that PMV may represent a marker of the capacity of the bone marrow to compensate for platelet turnover during acute phase of viral infection.
Conclusion, mild lung injury and high PMV were predictors for complete recovery. Low Hb at presentation, length of ICU stay, extensive lung injury, shortness of breath at presentation, and old age were predictors for persistent shortness of breath, while high Hb, extensive lung injury, and productive cough at presentation were predictors for persistent fatigue. A long-term follow up study is required for better understanding of the progression of post‐acute COVID‐19 persistent symptoms.
Funding: There were no external funding sources for this study.
Conflict of Interest: The authors declare that they have no conflict of interest.