Keywords
pediatric cancer - febrile illness - neutropenia - respiratory virus - bacterial infection
Key message
Molecular diagnostics can improve diagnostic sensitivity of febrile episodes in children
with cancer and help rationalize the management.
Introduction
Most cases of fever in children with cancer are treated empirically with antibiotics[1] and nearly three-fifths of febrile episodes without a focus or documented infection
have a respiratory pathogen identified in nasopharyngeal (NP) swab. For this reason,
the present study was performed which focuses on molecular identification of the respiratory
pathogens in samples collected from pediatric cancer patients presenting with fever
with or without respiratory illness.
Methodology
This is a prospective observational study to identify pathogenic etiology of febrile
episodes in pediatric cancer patients when on chemotherapy and study their clinical
outcomes.
Materials and Methods
Children under 18 years of age with malignancies on chemotherapy admitted as inpatients
with fever and either with a respiratory focus or no focus of infection during January
2019 to March 2020 were included in the study.
Those children with malignancies on chemotherapy admitted as inpatients with fever
but have microbiologically documented bacterial infection/focus were excluded. Each
new episode of fever in a child was considered a new episode of infection. A thorough
clinical evaluation by detailed history and physical examination was done in all admitted
patients at the onset of fever.
Laboratory tests included a complete blood cell count with differential leukocyte
count and platelet count; measurement of serum levels of creatinine and blood urea
nitrogen; and measurement of electrolytes, hepatic transaminase enzymes, and total
bilirubin. At least two sets of blood cultures were done simultaneously, with one
set collected from lumen of an existing central venous catheter, if present, and another
from a peripheral vein site; two blood culture sets from separate venipunctures were
sent if no central catheter is present.
Identification of respiratory viruses or bacteria (a panel total of 33 respiratory
pathogens) was done by multiplex real-time polymerase chain reaction (RT-PCR) from
NP swab. RT-PCR was done using Fast Track Diagnostics (FTD) kit, respiratory pathogen
21 plus kit (FTD Jung Linster, Luxembourg), which is a multiplex RT-PCR and can detect
20 viral and five bacterial pathogens.
Statistical Analysis
Statistical analysis was performed by the statistical software STATA 11.0. Continuous
variables were represented as “mean (standard deviation),” and categorical variables
were represented as “frequency (percentage).” Chi-square test or Fisher's exact tests
were used to assess differences in categorical data. Kruskal–Wallis tests were used
to find the difference in means of more than two independent data. The p-value of <0.05 is considered as significant.
Results
There were 40 episodes of febrile illness during the 15 months among 27 patients on
therapy for cancer. There was no gender predilection (male:female 14:13). The age
group ranged from 1 year 6 months to 11 years 4 months (mean and median age group
of 5 years). Majority of the patients had hematological malignancy (95%) as their
primary diagnosis. Half of the febrile episodes were observed in children less than
5 years.
NP swab was positive in 28 out of 40 episodes (70%) but in 12 episodes (30%) no pathogen
was identified. Seasonal predilection to monsoon and winter season for admission in
the hospital was evident in those with positive NP swab. There were 26 out of 28 episodes
admitted from September to March (92.85%) (inclusive of both years—2019 and 2020;
[Fig. 1]).
Fig. 1 Seasonal distribution of respiratory pathogens.
Respiratory symptoms were present in 19 out of 28 episodes with positive NP swab (67.86%),
but only in 6 out of 12 episodes with negative NP swab (50%; [Table 1]). The duration of hospitalization was comparatively lesser in NP-swab–positive isolates
than in negative swabs though not statistically significant. More than 50% (16/28)
had absolute neutrophil count (ANC) <1,000 and there were six episodes with ANC <100
in positive the NP swab category (21.42%). Whereas only 2/12 (16.66%) and 5/12 (41.7%)
in the negative NP swab category had ANC <100 and ANC <1,000, respectively. The duration
of antibiotics was more or less the same in both NP-swab–positive and negative episodes
(range: 7.53 ± 2.79 in positive and 8.75 ± 3.57 days in negative episodes). None of
the episodes were severe enough for intensive care unit (ICU) admission or oxygen
requirement. One episode of negative NP swab required ICU admission 10 days after
hospitalization in view of persisting fever and manifestation of central nervous system
symptoms. All the above categories of comparison like the respiratory symptoms, duration
of hospitalization, duration of antibiotics, and need for ICU admissions or oxygen
requirements were statistically not significant.
Table 1
Comparison between NP-swab-positive and -negative episodes
|
Nasopharyngeal swab
|
|
Positive
|
Negative
|
p-Value
|
|
Respiratory symptoms
|
0.285
|
|
Yes
|
19 (67.86%)
|
6 (50%)
|
|
No
|
9 (32.14%)
|
6 (50%)
|
|
Duration of hospitalization
|
4.32 ± 1.51
|
6.5 ± 5.35
|
0.1874
|
|
Absolute neutrophil count
|
0.369
|
|
< 1,000
|
16 (57.14%)
|
5 (41.67%)
|
|
> 1,000
|
12 (42.86%)
|
7 (58.33%)
|
|
Duration of antibiotics
|
7.53 ± 2.79
|
8.75 ± 3.57
|
0.4934
|
|
ICU/oxygen required
|
0.300
|
|
Yes
|
0 (0%)
|
1 (8.33%)
|
|
No
|
28 (100%)
|
11 (91.67%)
|
|
Type of malignancy
|
0.480
|
|
Hematological malignancy
|
26 (92.8)
|
12 (100)
|
|
Solid tumors
|
2 (7.1)
|
0
|
Abbreviation: NP, nasopharyngeal.
Among episodes with positive NP swab, the organisms identified were single respiratory
virus in 15/28 (53.57%), multiple viruses in 6/28 (21.42%), respiratory bacteria in
4/28 episodes (14.28%), and co-infection of both respiratory virus and bacteria in
3/28 (10.71%). Majority of viral episodes were symptomatic (18/28, 64.29%), irrespective
of whether the NP swab showed a single virus (12/15, 80%), multiple viruses (4/6,
66.67%), or viral co-infection with bacteria (2/3, 66.67%). In contrast, isolated
bacterial NP swabs were largely without respiratory symptoms (1/4, i.e., only 25%
with symptoms).
Out of the single organisms isolated through NP swab (virus: 15 and bacteria: 4),
the most common was Rhinovirus (RV; n = 9/19; 47.36%). Next in the prevalence was Streptococcus pneumoniae (n = 4/19; 21.05%) followed by human parainfluenza virus 3 (HPIV3; n = 3/19; 15.78%). Among the multiple organisms isolated, there were six episodes with
multiple viruses and three with combination of virus and bacteria ([Table 2]).
Table 2
Respiratory viruses and bacteria in episodes with positive nasopharyngeal swab: single
respiratory viral infection (bold) and co-infection
|
RV
|
Flu A
|
Flu B
|
H1N1
|
HPIV3
|
COR43
|
COR63
|
HRSV A
|
HRSV B
|
EV
|
SPN
|
|
RV
|
9
|
|
|
|
|
1
|
|
|
|
|
1
|
|
Flu A
|
|
1
|
|
1
|
|
|
|
|
|
|
1
|
|
Flu B
|
|
|
1
|
|
|
|
|
|
|
|
|
|
H1N1
|
|
1
|
|
|
|
|
|
|
|
|
|
|
HPIV 3
|
|
|
|
|
3
|
|
|
|
|
|
|
|
COR 43
|
|
|
|
|
|
1
|
|
|
|
|
|
|
COR63
|
|
1
|
|
|
|
|
|
|
|
|
|
|
HRSV A
|
|
|
|
|
|
|
|
|
1
|
|
|
|
HRSV B
|
|
|
|
|
|
|
|
|
|
|
|
|
EV
|
1
|
|
|
|
|
|
|
|
|
|
|
|
SPN
|
|
|
|
|
|
|
|
|
|
|
4
|
Abbreviations: COR 43, corona 43; COR 63, corona 63; EV, enterovirus; Flu A, influenza
A; Flu B, influenza B; HPIV3, human parainfluenza virus 3; HRSV A & B, human respiratory
syncytial viruses A and B; RV, rhinovirus; SPN, Streptococcus pneumoniae.
Note: There was one more episode of febrile neutropenia with four respiratory organisms
isolated not included in this table: RV + HRSV A + HRSV B + SPN.
On comparing the three most prevalent organisms identified in our study, we found
that RV and HPIV3 were prevalent in wider age groups starting from 1 year 5 months
to 8 years, whereas S. pneumoniae was prevalent among 4-to-6-year age groups ([Table 3]). Of all the variables, respiratory symptoms seem to be significant for viruses
(RV and HPIV3) than bacterial isolate (S. pneumoniae). None of the three organisms required prolonged hospitalization or oxygen therapy
or ICU admission. The most commonly used antibiotic as an empiric management as per
febrile neutropenia institutional protocol was piperacillin–tazobactam and aminoglycoside
was added when there was a clinical suspicion of resistant organism.
Table 3
Comparison table of the three most common respiratory pathogens
|
Single organism isolated through NP swab (n = 19)
|
Rhinovirus
(n = 9; 47.36%)
|
S. pneumoniae
(n = 4; 21.05%)
|
HPIV3
(n = 3; 15.78%)
|
p-Value
|
|
Age
|
0.6524
|
|
Mean
|
3.85 (1.53)
|
5.19 (0.43)
|
4.09 (3.41)
|
|
Median
|
3.48
|
5.15
|
2.5
|
|
Range
|
1.53–6.09
|
4.72–5.77
|
1.76–8.01
|
|
Gender
|
0.545
|
|
Male
|
5 (55.5)
|
1 (25)
|
1 (33.33)
|
|
Female
|
4 (44.4)
|
3 (75)
|
2 (66.67)
|
|
Type of malignancy
|
|
|
Hematological malignancy
|
9 (100)
|
4 (100)
|
3 (100)
|
|
Solid tumor
|
0
|
0
|
0
|
|
Respiratory symptoms
|
0.072
|
|
Yes
|
7 (77.77)
|
1 (25)
|
3 (100)
|
|
No
|
2 (22.22)
|
3 (75)
|
0
|
|
Absolute neutrophil count
|
0.906
|
|
< 1,000
|
5 (55.5)
|
2 (50)
|
2 (66.67)
|
|
> 1,000
|
4 (44.4)
|
2 (50)
|
1 (33.33)
|
|
Duration of hospitalization
|
3–7 days
|
2–5 days
|
3–4 days
|
0.6824
|
Abbreviations: HPIV3, human parainfluenza virus 3; NP, nasopharyngeal.
Discussion
Fever in children with cancer during chemotherapy is quite common owing to their immunocompromised
status.[2]
[3] This is one of the main causes of morbidity, delay in chemotherapy schedule, and
sometimes mortality.[4] These patients often are initiated on broad-spectrum antibiotics to cover serious
bacterial diseases.[5] Decision on discontinuation of antibiotics is also subjective[6] and hence adds up to indiscriminate use of antibiotics[1] and potential emergence of antibiotic resistance.[5]
The respiratory tract of immunocompromised patients becomes a vulnerable target for
microorganisms, pathogenic or opportunistic, as it is directly connected with the
environment.[6] In healthy children, respiratory viruses are usually confined to the upper respiratory
tract; in immunocompromised patients, owing to defects in innate and adaptive immunity
and frequent visits to hospital, respiratory infections can rapidly disseminate[6] and progress to the lower respiratory tract leading to respiratory distress and
pulmonary compromise.[5]
Routine chest X-ray is not recommended in the initial assessment of pediatric febrile
neutropenia[2] in the absence of respiratory symptoms. In recent years, significant progress has
been implemented in molecular techniques for the detection of respiratory pathogens
as compared with conventional methods of cell culture or antigen detection.[5] Although there are several studies on respiratory organisms in children with cancer,
there are limited reported studies on their detection by multiplex molecular amplification
assays (RT-PCR) in India.[1]
[7] Our study analyzed the RT-PCR positivity and correlated it with the respiratory
illness of patients with febrile episodes with or without neutropenia.
Our study could identify pathogens (either single virus or bacteria or multiple viruses
or co-infection) among 70% subjects through this technique, whereas it was 46% in
Torres et al[8] and 52% in Suryadevara et al's[9] studies. The reason for higher percentage in our study could be because we tested
for a larger panel of 33 respiratory pathogens unlike other studies. In our study,
half of the febrile episodes were observed in children less than 5 years, which is
almost similar to the study done by Soudani et al.[5]
RV was the most commonly identified pathogen in our study, similar to few other studies.[1]
[8]
[9]
[10] The next common organism was S. pneumoniae in contrast to other studies that had RSV as the second most common virus isolate.[8]
[10] The reason could be that these studies had only viruses in the respiratory panel
unlike our study which included bacteria also in the respiratory panel. We could also
find that there was co-presence of respiratory organism (either single virus or a
co-infection) detected in more than half of the febrile episodes with culture-positive
bacteremia. Since we needed to exclude the patients who had a microbiologically documented
infection or focus, we did not take them into our analysis.
We found that respiratory symptoms were present at admission in 67.86% of the episodes
with NP swab positive for respiratory virus or bacteria, which corresponds to studies
done by Torres et al[8] and Suryadevara et al.[9] We also noticed that those with positive NP swab for RV had obvious respiratory
symptoms compared to those with positive NP swab for S. pneumoniae or HPIV3, which was a statistically significant finding in our study. Similar to
the study done by Srinivasan et al,[10] we had more cases from September to March.
In our study, the duration of hospitalization was comparatively low in NP-swab–positive
episodes than in NP-swab–negative episodes, though it was statistically not significant.
None of the episodes had any adverse outcomes or ICU admissions. Likewise, in the
study by Torres et al,[3] all children with a positive respiratory virus detection, in the absence of a positive
bacterial detection, had a favorable outcome.
The increasing detection of respiratory organisms highlights the importance of optimizing
molecular diagnosis as part of the workup in cancer children when admitted for febrile
episodes while on chemotherapy. It, however, needs to be analyzed if the PCR positivity
actually represents the direct causative agent of the neutropenic fever or not, because
a positive PCR result could also represent a subclinical infection, a postinfection
viral shedding, or just intracellular nonreplicating viral nucleic acid remnants.
Limitations of this study were we had a small sample size and since all children admitted
were invariably initiated on empirical antibiotics as per febrile neutropenia institutional
protocol, we could not evaluate the clinical course of positive NP swabs in the absence
of antibiotic use. Furthermore, we also did not involve any control group to conclude
if the NP swab results are to be taken as an acute infection or as commensals in the
throat.
Conclusion
In our study, the PCR-based diagnostics could identify around 70% of respiratory pathogen
in febrile episodes without a focus or documented infection. PCR-based diagnostics
for respiratory pathogens can greatly enhance the management of patients with febrile
neutropenia where standard tests show no documentation of cause of the infection.
In the future, application of agile and broad microbial diagnostics may provide decreased
use of antibiotics and individualize infection management.
