Discussion
The results of this study showed that MPV, which can be rapidly and
safely measured, has significant predictive value for the diagnosis of
COVID-19. In addition, regardless of the threshold values, MPV was seen
to have better predictive capacity than lymphocyte values.
In reports from several countries, it has been stated that children
infected with COVID-19 are mild, or more often asymptomatic carriers,
and thus play a major role in the spread of the disease. By spreading
the disease, delayed diagnosis of asymptomatic children may be a reason
for increased morbidity and mortality (10). Although RT-PCR or genetic
sequencing used in COVID-19 diagnosis are the gold standard, these
methods are not available in all centres, and they are expensive (19,
20). Therefore, there is a need for a simpler and more practical method.
Leukocyte, neutrophil, lymphocyte and platelet counts, and CRP level are
simple parameters, most of which are provided by an automatic hematology
analyser readily available on the market.
In a study of adult patients by Huang C et al (21), there was determined
to be lymphopenia in 63% of cases, leukopenia in 25% and leukocytosis
in 30%, no significant change was found in neutrophil values, and
thrombocytopenia was determined to have developed in 5%. Liu et al (22)
reported that the most common laboratory abnormalities in adult patients
were lymphopenia and decreased lymphocyte percentage. Low lymphocyte
levels were associated with the viral load of COVID-19 determined in the
respiratory tract and the severity of the disease.
In the early laboratory values of a study of paediatric patients by
Sehen et al (19), leukocyte count was determined to be normal or low,
and an increase was determined in lymphopenia and CRP level. In a study
by Chen et al (23), it was reported that CRP could be normal or high in
paediatric patients. Consistent with these findings in literature,
lymphocyte measurements in the current study were determined to be
significantly low in COVID-19 positive patients. Although the leukocyte,
neutrophil, and platelet counts were lower than those of the control
group, this decrease was not determined to be statistically significant
(p>0.05). No significant difference was determined between
the groups in respect of the CRP levels.
MPV is a simple, inexpensive, and easily obtained biomarker of
thrombocyte function, and can be measured in almost all laboratories.
Thrombocyte volume shows a correlation with thrombocyte function and
activation (24). In addition to primary hemostatic functions,
thrombocytes play a role in the pathogenesis of infectious diseases
(25). Previous studies have suggested that megakaryocyte ploidy may be
affected by cytokines such as IL-3 and IL-6, and this could lead to
greater and more reactive production of thrombocytes (26).
Acute hepatitis A is characterised by a low or only moderate level of
acute phase reaction, especially in children with an asymptomatic course
(27). Torre et al (28) reported an increase in IL-1a, IL-6, and TNF-a
serum levels in the acute phase of acute hepatitis A disease. In a study
of patients diagnosed with hepatitis A by Akin et al (29), an increase
was determined in MPV values and it was reported that increased
pro-inflammatory cytokines could contribute to the increase in MPV
values. Gao et al (30) determined that IL-6 levels increased in
proportion with the severity of the disease in patients diagnosed with
COVID-19. High levels of IL-6 in COVID-19 may be a result of increasing
MPV. Based on these observations of MPV, it can be concluded that this
inflammation marker could be used for the diagnosis of COVID-19.
To the best of our knowledge, this is the first study to have
investigated the relationship between MPV and COVID-19. Of the
inflammatory markers examined in this study, COVID-19 was not determined
to have caused any significant change in WBC, neutrophil and platelet
counts or CRP level, and consistent with literature, a significant
decrease was determined in lymphocyte count. When a cutoff value of
≥8.74 fl MPV was used in the prediction of COVID-19, sensitivity and
specificity were 81.82% and 95.00% respectively and positive and
negative predictive values were 93.75 and 85.07, respectively. A cutoff
value of ≤2.12 mm3 used for lymphocytes had
sensitivity of 49.09% and specificity of 86.67% in the prediction of
COVID-19 with positive and negative predictive values of 77.14 and
65.00, respectively. Based on the ROC curve analysis, the sensitivity,
specificity, positive and negative predictive values of MPV were higher
than those of lymphocytes.