4 | DISCUSSION
We found that the IPF, which is a new platelet index, was greater in
patients with acute bronchiolitis than in healthy individuals and was
positively correlated with the clinical severity of acute bronchiolitis.
To our knowledge, this is the first study to investigate the
relationship between acute bronchiolitis and IPF. Some cytokines and
mediators are activated as part of the response to inflammatory
conditions. Inflammation mediates the activation of endotoxins and
cytokines, causing immature reticulated platelets (i.e., IPF) to
be transferred from the bone marrow to peripheral blood. Platelets
stimulate receptors as part of the inflammatory response to pathogens,
and interleukins are released to suppress
inflammation8–10. Therefore, the IPF is a biochemical
and hematological systemic inflammatory marker that can function as an
index of platelet activation and production rate in the bone
marrow11. Diagnostic accuracy studies performed over
the last few years suggest that IPF levels can provide clinically
relevant information regarding inflammatory activity and disease
prognoses4,11,12. Roberto et al . reported that
IPF levels increased in patients with sepsis before sepsis was observed
clinically, and they also found that IPF was a better biomarker for
sepsis than procalcitonin or C-reactive protein13.
Park et al . found that IPF levels were significantly higher in
patients with sepsis than in individuals who did not have
sepsis5. Rodolfo et al . evaluated the IPF as a
biomarker for sepsis diagnosis and severity and found that it was
correlated with sepsis severity scores and had the highest diagnostic
accuracy for sepsis among all the clinical and laboratory parameters
assessed14. Another study found that IPF was strongly
positively correlated with MPV and PDW, and attributed this to an
increase in the number of larger and wider platelets that appeared after
the destruction of pro-inflammatory cytokines and endotoxins as part of
a severe inflammatory response15. Together, these
findings suggest that IPF levels increase in inflammatory diseases such
as sepsis and may be used as an indicator of the inflammatory response.
Our observation that the IPF was greater in patients with acute
bronchiolitis than in healthy individuals is consistent with previous
studies. The clinical severity of acute bronchiolitis was positively
correlated with the IPF. Therefore, patients with acute bronchiolitis
and high IPF values should be monitored closely after admission to the
emergency department. IPF values higher than 3.2% had a specificity of
97% and a sensitivity of 84% for clinical deterioration of acute
bronchiolitis.
Platelets play an important role in inflammatory responses, and the PLT
increases in many inflammatory diseases. Studies have found that
patients with acute bronchiolitis have higher PLTs than healthy
individuals16,17. Our patient group had significantly
greater PLT values than our healthy control group, and this observation
is consistent with previous studies. Our severe bronchiolitis group had
higher PLT values compared to our mild bronchiolitis group, but the
difference was not statistically significant. During an inflammatory
response, depolymerization occurs in the microtubular structure of
platelets, and changes also occur in the structure of actin that becomes
polymerized; consequently, platelets change their shapes and these
changes are reflected in the MPV18. Changes in MPV can
be observed before changes in platelet number, so changes in MPV may be
useful for predicting inflammation at an early stage and determining its
subsequent severity19–21. Among our study population,
the MPV was significantly higher in those with moderate and severe
bronchiolitis than in those with mild bronchiolitis or in healthy
controls, so MPV values may be used to estimate prognoses and the
severity of acute bronchiolitis; patients with an MPV value greater than
9 fL should be monitored carefully for clinical deterioration. Several
previous studies have evaluated the relationship between acute
bronchiolitis and MPV. Gökçe et al .22 found
that patients with acute bronchiolitis had higher MPVs than their
healthy counterparts, but found no statistically significant differences
in MPVs between different bronchiolitis groups. Higher MPVs were
observed in children with influenza A respiratory tract infections than
in healthy children23. MPVs were also found to be
higher in children with pneumonia, asthma, or sepsis than in healthy
children24–26. Gasparyan et
al .27 found that MPV values were increased in
patients with mild inflammation, and they attributed this finding to the
transfer of large activated platelets to the site of infection as the
severity of inflammation increased. Together, these results suggest that
the MPV may also be used to estimate prognoses and the severity of other
inflammatory diseases.
PDW, another platelet volume index, shows the variation in platelet
diameters and varies by platelet activation. An increase in PDW may
occur as a result of swelling, disruption, or platelet
immaturity20. In our study, PDW values were
significantly greater in patients with moderate and severe bronchiolitis
cases than in those with mild bronchiolitis or healthy controls. Ergulet al . found greater PDW values in children with acute
bronchiolitis than in healthy children17. PDW may also
be greater in patients with sepsis than in healthy individuals, and may
be used as a prognostic indicator for patients with
sepsis26,28.
The present study had some limitations. It was not a multi-center study.
Additionally, we did not characterize the viruses that cause acute
bronchiolitis and compare the corresponding clinical severities. The IPF
is a novel indicator of inflammation, and it is also a new marker for
diagnosing and evaluating the clinical severity of acute bronchiolitis.
Larger prospective studies are needed to clarify the clinical
significance of using IPF values to assess patients with acute
bronchiolitis.
ACKNOWLEDGMENTS
This study received no specific grant from any funding agency in the
public, commercial, or not for profit sectors.
CONFLICT OF INTERESTS
The author declares that there are no conflict of interests
AUTHOR CONTRIBUTIONS
Concept and design: MD, MK, MAÖ, MH. Acquisition, analysis, or
interpretation of data: MD, HA, MH. Drafting of the manuscript: MAÖ, MK,
MD, MH. Critical revision of the manuscript for important intellectual
content: MAÖ, MK, HA, MD. Statistical analysis: MD,HA. Administrative,
technical, or material support: MAÖ, MK, MD. Supervision: MD, MK, MH.