Keywords
C-reactive protein - febrile neutropenia - interleukin-6
Introduction
Systemic infection leading to multi-organ failure during episodes of neutropenia is
one of the major causes of treatment-related mortality in children on chemotherapy.[1] Fever is the first symptom of infection in neutropenic patients. However, apart
from infection, fever can also be due to reaction to drugs, blood products, and tumor-associated
fever.[1]
Empirical antibiotic therapy is usually started immediately when fever develops in
neutropenic patients as bacterial infections can be life-threatening for such patients.
Therefore, reliable markers are needed to diagnose or rule out infection, which will
reduce the use of empirical broad-spectrum antibiotics and facilitate targeted and
specific therapy as soon as possible. The most common marker used is C-reactive protein
(CRP), an acute-phase reactant whose concentration rises within 24 h of a microbial
infection. Interleukin-6 (IL-6) is a cytokine whose levels increase after stimulation
with IL-1, endotoxin or tumor necrosis factor alpha.[1],[2] Although the concentration of both IL-6 and CRP is higher in patients with infections
caused by bacteria as compared to viruses, IL-6 has been reported as a more sensitive
and early marker for bacteremia especially Gram-negative bacteremia.[3],[4] IL-6 levels have been studied to rise as early as 1 h after the infectious stimulus.[5]
Febrile neutropenia in cancer patients on chemotherapy increases the duration of hospital
stay and cost of treatment and leads to significant morbidity and mortality. Mortality
from febrile neutropenia has been reported to be 5% in solid tumors and 11% in hematological
malignancies. Prognosis is worst in patients with proven bacteremia with mortality
rates of 18% in Gram-negative and 5% in Gram-positive bacteremia.[6]
Therefore, the present study aimed to analyze the role of IL-6 as a marker for bacteremia
in pediatric patients with febrile neutropenia. The other objectives of the study
were to compare the levels of IL-6 versus CRP in microbiologically documented infections
(MDIs), clinically documented infections (CDIs), and fever of unknown origin (FUO);
and to study the prognosis and outcome of the three groups in febrile neutropenia.
Materials and Methods
Ethics
The study was approved by the Institutional Ethics Committee (ECR/146/Inst/KA/2013).
An informed consent was taken from the parents of all study participants after explaining
the purpose and relevance of the study to them.
Study design
A prospective observational study was conducted over a period of 18 months from January
2018 to June 2019 in the Paediatrics Department of a Tertiary Care Center in South
India.
Study participants
All children aged from 1 month to 18 years having a diagnosis of hematological or
other malignancies who developed febrile neutropenia during any phase of chemotherapy
were included in the study. Multiple episodes of febrile neutropenia in the same child
were analyzed as separate episodes. The study participants who were not willing to
participate in the study and those who were discharged against medical advice were
excluded from the study.
Definitions used:
-
Fever: Fever is defined as a single temperature measurement of >38.3°C (101°F) or
a temperature of >38.0°C (100.4°F) sustained over a 1 h period[7]
-
Absolute neutrophil count (ANC): white blood cell × (%neutrophils + %bands + other
precursor cells)
-
Neutropenia: neutropenia is defined as an ANC of <500 cells/mm3 or an ANC that is
expected to decrease to <500 cells/mm3 during the next 48 h[7]
-
Profound neutropenia: ANC is <100 cells/mm3[7]
-
Prolonged neutropenia: Neutropenia lasting for more than 7 days
-
FUO: New onset of fever without clear clinical or microbiological evidence; fever
> 38.3°C or > 38.0°C over at least 1 h or twice within 12 h without evident cause[8]
-
CDI: Fever in connection with unambiguous diagnostic signs of localized infection,
for example, pneumonia, acute gastroenteritis, urinary tract infection, skin/soft-tissue
inflammation without microbiological proof or if not accessible for examination[8]
-
MDI: fever with plausible pathogenic evidence (in the microbiological/time context)
in addition to identified localized infection, or pathogenic agents can be found in
blood culture without localized infection.[8]
Data collection procedure
A detailed history was obtained including demographic data, primary diagnosis, details
of chemotherapy regime, and any prior antibiotic prophylaxis. Blood samples were collected
at the onset of fever in inpatients or within 6 h of presentation to the hospital
and sent for complete blood counts, erythrocyte sedimentation rate, CRP, IL-6, renal
and liver function tests, blood culture, and sensitivity. Additional tests and investigative
procedures such as urine routine, chest X-ray, and lumbar puncture were done if indicated.
Antibiotics received were documented, prognosis and outcome were analyzed.
Sample size
Anticipating sensitivity of 70% for IL-6 as a marker of bacteremia with a 4% precision
and 20% prevalence of MDI, minimum of 57 cases of febrile neutropenia were to be enrolled
in the study.
Statistical methods
Data were analyzed using the IBM SPSS Statistics 20. Descriptive data were expressed
as percentage, median, and interquartile range (IQR) or as mean and standard deviation.
Statistical significance was calculated using Student's t-test for parametric data
and Kruskal–Wallis test for nonparametric data. The association between categorical
variables was assessed using Chi-square test or Fisher's exact test.
Results
A total of 32 episodes of febrile neutropenia in 25 children were analyzed.
The baseline characteristics of the study participants were as mentioned in [Table 1]. The majority of the study participants were <6-year-old males. The median age for
the study group was 7 years (IQR: 4,12). Nutritional status was normal in 21 out of
25 children in the study group. The predominant malignancy in the study group was
acute lymphoblastic leukemia (ALL) (84%). Among children diagnosed to have ALL (21),
most of them had CALLA positive B-cell ALL (15, 71.4%). There was one case of Hodgkin's
lymphoma (mixed cellularity Stage 2), one case of non-Hodgkin's lymphoma and one case
of extra-adrenal metastatic neuroblastoma (Stage 4).
Table 1
Baseline characteristics of the study group (n=25)
|
Characteristic
|
n (%)
|
|
ALL=Acute lymphoblastic leukemia, AML=Acute myeloid leukemia
|
|
Gender
|
|
|
Male
|
18(72)
|
|
Female
|
7 (28)
|
|
Age group
|
|
|
1 month-6 years
|
12 (48)
|
|
7-12 years
|
8 (32)
|
|
13-18 years
|
5 (20)
|
|
Weight
|
|
|
Normal
|
21 (84)
|
|
Underweight (weight < 3rd centile)
|
4 (16)
|
|
Primary diagnosis
|
|
|
ALL
|
21 (84)
|
|
AML
|
1 (4)
|
|
Lymphoma
|
2 (8)
|
|
Solid tumor
|
1 (4)
|
The characteristics of the febrile neutropenia episodes are mentioned in [Table 2]. Febrile neutropenic episodes were seen more in the induction stage of chemotherapy.
Organisms isolated in the seven cases of MDI were Klebsiella pneumoniae (in three
cases), Pseudomonas aeruginosa (in two cases), coagulase-negative Staphylococcus and
Staphylococcus haemolyticus in one case each. One case of K. pneumoniae sepsis also
had Aspergillosis. There was a central line in situ in this case. Two children had
Varicella zoster infection and one had herpes labialis. The most common focus of infection
was lower respiratory tract infection confirmed by radiological evidence (14 cases).
The second-most common source of infection was acute gastroenteritis (nine cases).
Three cases with acute gastroenteritis also had mucositis. Multisystem involvement
was seen in six cases and two out of these had hypotension and shock at presentation.
Table 2
Characteristics of the febrile neutropenia episode (n=32)
|
Characteristic
|
n (%)
|
|
MDI=Microbiologically documented infection, CDI=Clinically documented infection, FUO=Fever
of unknown origin
|
|
Stage of chemotherapy
|
|
|
Induction
|
14 (43.8)
|
|
Consolidation
|
12 (37.5)
|
|
Maintenance
|
6 (18.7)
|
|
Type of infection
|
|
|
MDI
|
7 (21.9)
|
|
CDI
|
19 (59.4)
|
|
FUO
|
6 (18.7)
|
|
Relapse of malignancy
|
|
|
Yes
|
3 (9.4)
|
|
No
|
29 (90.6)
|
|
Steroids in last 2 weeks
|
|
|
Yes
|
28 (87.5)
|
|
No
|
4 (12.5)
|
Twenty-four out of 32 cases had hemoglobin of <11 g/dl. Eleven cases required packed
red blood cell transfusion. Thrombocytopenia (platelet count <150,000/mm3) was seen
in 21 cases. Platelet transfusion was given in ten cases which had severe thrombocytopenia
with bleeding manifestations. Profound neutropenia was seen in 18 cases. Granulocyte-colony
stimulating factor was given in seven cases. Two cases had deranged baseline renal
function test (elevated creatinine value more than the age-related upper normal limit)
and four cases had deranged liver function test (elevated transaminases more than
1.5 times the age-related upper normal limit) out of which two were drug-induced hepatitis.
The median values of IL-6 and CRP in the febrile neutropenia episodes are mentioned
in [Table 3]. It was noted that IL-6 was high in all the 32 episodes of febrile neutropenia.
IL-6 values ranged from 8 to 5000 pg/ml. In 14 episodes, IL-6 value was more than
100 pg/ml. Gram-negative sepsis had a much higher median IL-6 value than Gram-positive
sepsis and sterile blood cultures (P = 0.017). Similar observation was not seen with
CRP values (P = 0.796, statistical tool used: Kruskal–Wallis test). CRP was high in
26 out of 32 episodes of febrile neutropenia. All the six episodes which had normal
CRP values had sterile blood culture and CDI. CRP values ranged from 0.66 to 288 mg/L.
The median value of both IL-6 and CRP was highest in MDI.
Table 3
Median value of interleukin-6 versus C-reactive protein in febrile neutropenic episodes
|
IL-6 (pg/ml) (≤7 pg/ml)
|
CRP (mg/L) (≤10 mg/L)
|
|
IL=Interleukin, CRP=C-reactive protein, MDI=Microbiologically documented infection,
CDI=Clinically documented infection, FUO=Fever of unknown origin
|
|
All febrile neutropenic episodes: (n=32)
|
73.9 (25.2-151.5)
|
52.6 (18-122.2)
|
|
Type of infection
|
|
|
|
MDI (n=7)
|
129 (27-200.1)
|
68 (33.9-103)
|
|
CDI (n=19)
|
48 (25-128)
|
44.2 (3.9-125.7)
|
|
FUO (n=6)
|
85 (12.7-120.7)
|
55.5 (28.4-196.8)
|
|
Blood culture
|
|
|
|
Gram-negative (n=5)
|
169 (124-2600)
|
60.7 (25.8-188.6)
|
|
Gram-positive (n=2)
|
17.5
|
85.5
|
|
Sterile (n=25)
|
52 (21-120)
|
44.2 (8.6-127.5)
|
[Table 4] shows the correlation between type of infection and ANC. All the seven cases of
MDI were associated with ANC < 100/μL.
Table 4
Correlation between absolute neutrophil count and type of infection (n=32)
|
Type of infection
|
ANC, n (%)
|
|
≤100
|
101-500
|
>500
|
|
ANC=Absolute, MDI=Microbiologically documented infection, CDI=Clinically documented
infection, FUO=Fever of unknown origin
|
|
MDI (n=7)
|
7 (100)
|
0
|
0
|
|
CDI (n=19)
|
7 (18.2)
|
10 (63.6)
|
2 (18.2)
|
|
FUO (n=6)
|
4 (66.6)
|
2 (33.4)
|
0
|
The median duration of fever in the febrile neutropenia episodes was 4 days (IQR:
2,7). Fever beyond 1 week duration was seen in eight out of 32 episodes (25%). Prolonged
neutropenia was seen in 22 cases. Four cases of febrile neutropenia succumbed due
to septic shock in the present study. All the four cases had an IL-6 value of >100
pg/ml.
The correlation between the outcome of febrile neutropenic episodes and type of infection
is shown in [Table 5]. MDI were associated with the worst prognosis as three cases succumbed in this group,
42.9% of the cases had fever beyond 1 week and prolonged neutropenia was seen in 85.8%
of the cases.
Table 5
Correlation between the outcome of the febrile neutropenic episode and type of infection
(n=32)
|
Outcome
|
Type of infection, n (%)
|
|
MDI (n=7)
|
CDI (n=19)
|
FUO (n=6)
|
|
MDI=Microbiologically documented infection, CDI=Clinically documented infection, FUO=Fever
of unknown origin
|
|
Primary outcome
|
|
|
|
|
Survived
|
4 (57.1)
|
18 (94.7)
|
6 (100)
|
|
Succumbed
|
3 (42.9)
|
1 (5.3)
|
0
|
|
Duration of fever
|
|
|
|
|
(days)
|
|
|
|
|
≤7
|
4 (57.1)
|
15 (78.9)
|
5 (83.3)
|
|
>7
|
3 (42.9)
|
4 (21.1)
|
1 (16.7)
|
|
Duration of
|
|
|
|
|
neutropenia (days)
|
|
|
|
|
≤7
|
1 (14.2)
|
7 (36.8)
|
2 (33.3)
|
|
>7
|
6 (85.8)
|
12 (63.2)
|
4 (66.7)
|
|
Duration of break
|
|
|
|
|
in chemotherapy
|
|
|
|
|
(days)
|
|
|
|
|
≤7
|
1 (14.2)
|
6 (31.6)
|
2 (33.3)
|
|
>7
|
6 (85.8)
|
13 (68.4)
|
4 (66.7)
|
Discussion
Most of the childhood cancers have a male preponderance with a male to female ratio
of 1.2:1.[9],[10] However, in the present study, a male to female ratio of 2.5:1 was seen. The most
commonly seen childhood cancer in India is leukemia which accounts for 25%–40% of
all the cancers.[11] In the present study, 84% of the children had ALL.
The incidence of bacteremia in febrile neutropenic children depends on extent and
duration of neutropenia, antibiotics prophylaxis and use of central venous catheters.
The incidence rate of bacteremia ranges from 5% to 35% in febrile neutropenic children
who are not receiving antibiotic prophylaxis.[8],[12] In the present study, all the children were receiving antibiotic prophylaxis and
the incidence of bacteremia was 21.9%. A change in the trend of bacterial agents causing
bloodstream infections in febrile neutropenic patients has been seen due to the routine
use of antimicrobial prophylaxis. In the 1960s–1970s, a predominance of Gram-negative
bacteria was seen but over the last few decades, Gram-positive bacteria are isolated
more often.[13] However, Gram-negative organisms are still associated with significant mortality
and in some of the recent studies, Gram-negative bacteremia has been seen more commonly
than Gram-positive bacteremia.[13],[14] In the present study also, in 5 out of 7 cases of MDI, Gram-negative bacteremia
was seen and 3 cases of Gram-negative bacteremia succumbed. All the cases of MDI had
profound neutropenia and majority had prolonged neutropenia. Therefore, febrile profound
neutropenic patients need to be started on appropriate antibiotic therapy at the onset
of symptom of fever.
Febrile neutropenic patients need to be started on antibiotics as early as possible
to reduce the associated morbidity and mortality. Therefore, markers predicting the
risk and type of bacteremia can help in better treatment and prognostication of the
febrile neutropenic episode. IL-6 has been reported as a more sensitive marker of
Gram-negative sepsis.[1],[4] In the present study, the median value of Il-6 was 3–10-fold higher in Gram-negative
sepsis as compared to Gram-positive sepsis and sterile blood cultures. Similar trend
was not observed with CRP. A larger randomized study taking into account other contributing
factors such as levels of CRP and IL-6 in viral and fungal infections; risk of mortality
and cost-effectiveness can provide more concrete evidence toward this observation.
However, CRP remains a cheaper and useful marker of sepsis as the median values of
both IL-6 and CRP was highest in MDI.
Higher IL-6 levels have also been associated with an increased risk of mortality and
an association between mean concentration of plasma IL-6 over time and the mortality
rate has been studied.[15],[16] However, due to financial constraints, serial IL-6 values could not be obtained.
Conclusion
IL-6 is a better predictor of Gram-negative bacteremia than CRP in febrile neutropenic
children while on chemotherapy. However, the statistical significance of this association
could not be ascertained due to the small sample size
CRP estimation is cheaper and is still a valuable test in sepsis where IL-6 test is
not feasible.
