Utility of serial procalcitonin measurement in management of febrile neutropenia in a resource constrained setting.

Background: Febrile neutropenia is a common cause in morbidity and mortality during treatment of hematological neoplasms. Methods: Subjects included all cases admitted under hematology department with febrile neutropenia from February to June 2018. Diagnostic work up for each febrile episode was done including Procalcitonin (PCT) was sent at fever onset 0,24,48hour, day 7 and day 14. Results: Data was analyzed for 52 febrile episodes in 50 patients.PCT cut off value at 24 hours of ≤1.2ng/ml had a sensitivity and specificity of 62.5% and 87.5% for discriminating IFI and MDI (p=0.033). PCT had a negative predictive value of 70% for the diagnosis of IFI as compared to MDI. PCT cut-off of 0.4ng/ml on day 7 had a sensitivity and specificity of 60.98% and 100% respectively for discriminating IFI and PUO (p= 0.0001). There was a significant fall in the level of PCT by day 14(median fall in PCT of 10.8) in the group of patients who had both IFI+ MDI when compared to other groups (p=0.047). PCT level at 24 and 48hours can be a predictor of severity of infection. Conclusion: Procalcitonin at 24 hours could discriminate between bacterial and fungal infection and between fever due to fungal infection and disease fever.


Introduction
Febrile neutropenia (FN), as defined by the Immunocompromised Host Society (ICHS) [1], is either presence of fever with an absolute neutrophil count (ANC) of <500 cells/mm3 or presence of fever with an ANC of <1000 cells/mm3 with an expected decline to <500 cells/mm3. Febrile neutropenia (FN) is a frequent complication seen in hematological malignancies and this warrants prompt institution of antibiotics. Sometimes it is seen secondary to the hematological disease itself and frequently in the patients on chemotherapy. Often, the etiology of fever is difficult to ascertain in acute leukemia 3 patients. According to European Society of Medical Oncology (ESMO) Clinical Practice Guidelines, positive microbiological culture is found only in 7-31 % of febrile episodes [2]. Also, the clinical criteria for systemic inflammatory response syndrome (SIRS) may fail due to the presence of neutropenia [2]. Without early adequate treatment, the disease may become rapidly fatal [3].
In hemato-oncology setting, larger studies of serial measurements of PCT in febrile neutropenic patients are lacking and most are inconclusive because of small sample sizes and different PCT cut-off values employed.

Materials And Methods
It was a prospective observational study conducted in the Department of Hematology and Reproductive Biology, AIIMS, New Delhi from February 2018 to July 2018. Patients admitted with hemato-lymphoid malignancies or aplastic anemia with febrile neutropenia (ANC < 500/mm3) aged 1 year to 60 years.
A written informed consent will be obtained from all the included patients/ patients' parents (in case of minor) prior to the study as mandated by the institute ethics committee.
Fever was defined as a single oral temperature measurement of >38.3C (101F) or a temperature of >38.0C (100.4F) sustained over a 1-h period. A new febrile episode was defined as a relapsing fever after more than 72 hours of apyrexia (>38 0 C). Neutropenia was 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. Bacteremia will be defined as fever with positive with positive blood cultures for bacteria

Procalcitonin Measurement
During each febrile episode, blood samples for PCT was sent at the same time as blood cultures at the onset of fever before starting I.V. antibiotics and thereafter at 24 hr, 48hr, day 7, day 14 or till 5 resolution of fever whichever is later and at the end of antibiotics (6 times for each febrile episode/ patient).

Statistical Analysis
Statistical analysis was done using SPSS statistics version 20.  and on day 7 were significantly higher in the group undergoing Induction 2(salvage) chemotherapy.

Procalcitonin in septic shock
The median PCT value at 24 and 48 hours of febrile neutropenia was significantly higher in the group of patients who developed signs of severe infection like Septic shock, hypoxia (p value-0.007 for PCT 24 and 0.001 for PCT 48). 7 The median PCT values were higher on day 7 and day 14 when comparing febrile events due to infectious etiology against disease fever/ Pyrexia of Unknown Origin (PUO).
However, the PCT values were not different at fever onset but the values were nonsignificantly higher at 24 and 48-hour of the febrile episode.

Procalcitonin Dynamics
The That means if PCT at 24 hours was less than or equal to 1.2 then there are significantly higher chances of presence of IFI in the patient as compared to MDI-B. 8

When comparing the PCT values for invasive fungal infections versus other bacterial
infections (MDI/CDI), there was no significant difference in the two groups.
The ROC curves for PCT at other time points were not statistically significant.
After performing ROC, cut off point of PCT at Day 7 (Figure 3b) was >0.4 with AUC of .813 and sensitivity and specificity of 60.98% and 100% respectively for discriminating IFI and PUO (disease fever) which was statistically significant with p value =.0001. It means if PCT at Day 7 of fever was more than or equal to 0.4 then there are significantly higher chances of fever being due to IFI in the patient as compared to disease fever (PUO). ROC curves for IFI vs MDI for PCT at 0hr of fever and 48 hours of fever has been shown below.

Diagnostic performance of PCT for infectious versus non-infectious etiology of fever
The cut-offs obtained for PCT draws at 0, 24 and 48 hours were not statistically significant. However, the PCT cut-off of 0.4ng/ml on day 7 had a sensitivity, specificity, NPV and PPV of 60.98%,100%,27.3% and 100% respectively with AUC 0.813 (p<0.0001).

Discussion
Procalcitonin has been studied as a marker of infection to in patients of febrile neutropenia. To the best of our knowledge, we are aware of only 4 studies who have studied procalcitonin serially ( HSCT subjects as well in their study [9]. The median age of the cohort in our study was 46.5 years which is much less when compared to the cohort in Robinson et al where the median age of the subjects was 57 years [9]. One plausible explanation for this observation could be because of 46% febrile episodes in their study included subjects of myeloma/lymphoma which is usually the disease of the elderly. We had a significant burden of gram-negative infections with most common being Klebsiella pneumonia (37.5%) and significant number of patients fell into 2 or more groups of infections. E. coli (27.5%) followed by other gram-negative bacteria (Acinetobacter spp., Pseudomonas) were the most common organism. [17][18]  which was restricted to studying only bacteremia, they did not include any group with CDI [16].
PCT values in the MDI group peaked on day 7. PCT seems to be an exquisitely specific marker of bacteremia because irrespective of presence of any other cause of fever PCT values were highest on day 7 in MDI when compared to the PUO/CDI (only)/PUO groups.
Robinson et al in their study found that the PCT values were significantly higher in non-CNS MDI when compared to all other etiologies of fever [9]. They found that the peak PCT was seen 2 days after onset of fever which was usually the time, they re-evaluated their empirical antibacterial therapy. At our center our antibiotic policy is to change the antibiotics at 48-72 hours of fever not responding to empirical antibiotics and the response was seen about 48 to 72 hours after reviewing the first line antimicrobials.

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The PCT values in our study rose to their peak at 48 hrs in the IFI group. Robinson et al in their study found that a PCT >500pg/ml beyond 3 days of fever had a sensitivity of 81%, specificity of 57%, PPV 49%, NPV 86% to diagnose fungal infection and it occurred around day 7 in their study [9].
The MDI+IFI is a unique group which has not been highlighted in other studies. Though the numbers are small (n=3) but this has not been forthcoming in any other studies.
At fever onset the median PCT was highest in this group but it was not statistically HSCT subjects as well in their study [9]. The median age of the cohort in our study was 46.5 years which is much less when compared to the cohort in Robinson et al where the median age of the subjects was 57 years [9]. One plausible explanation for this observation could be because of 46% febrile episodes in their study included subjects of myeloma/lymphoma which is usually the disease of the elderly.
We had a significant burden of gram-negative infections with most common being Klebsiella pneumonia (37.5%) and significant number of patients fell into 2 or more groups of infections. E. coli (27.5%) followed by other gram-negative bacteria (Acinetobacter spp., Pseudomonas) were the most common organism. [17][18]  patients were critically ill. This is most likely because most of our infections were caused due to gram-negative bacteria and they are known to cause severe sepsis.
The median highest PCT values were seen 48 hours after onset of fever in the CDI group.
When the CDI was having a MDI(n=9) too, the median PCT values were highest on day 14.
It means the CDI group responded to the empirical antibiotic regimen and hence within 48 hours the PCT values started to fall. But when CDI was associated with an MDI the 14 antibiotic regimen was not appropriate and hence the PCT values kept rising and had a late response when the antibiotics were changed. Reitman et al compared PCT values which was restricted to studying only bacteremia, they did not include any group with CDI [16].
PCT values in the MDI group peaked on day 7. PCT seems to be an exquisitely specific marker of bacteremia because irrespective of presence of any other cause of fever PCT values were highest on day 7 in MDI when compared to the PUO/CDI (only)/PUO groups.
Robinson et al in their study found that the PCT values were significantly higher in non-CNS MDI when compared to all other etiologies of fever [9]. They found that the peak PCT was seen 2 days after onset of fever which was usually the time, they re-evaluated their empirical antibacterial therapy. At our center our antibiotic policy is to change the antibiotics at 48-72 hours of fever not responding to empirical antibiotics and the response was seen about 48 to 72 hours after reviewing the first line antimicrobials.
The PCT values in our study rose to their peak at 48 hrs in the IFI group. The peak PCT in the IFI group was not statistically different from the MDI group. Most of the IFI s in our study were of probable fungal infection, proven fungal infections were seen in only 3 cases (all were Aspergillus spp.) and no case of invasive candidiasis was found. A PCT value at 24 hours of ≤1.2 with AUC of 0.766 had a sensitivity and specificity of 62.5% and 87.5% for discriminating IFI and MDI (p=0.033). Also, PCT had a negative predictive value of 70% for the diagnosis of IFI when compared to MDI.
When PCT was compared to PUO at day 7, a value of 0.4 with AUC of 0.813 had a sensitivity and specificity of 60.98% and 100% for discriminating IFI and PUO with statistically significant value of 0.0001.
Robinson et al in their study found that a PCT >500pg/ml beyond 3 days of fever had a sensitivity of 81%, specificity of 57%, PPV 49%, NPV 86% to diagnose fungal infection and it occurred around day 7 in their study [9].
The MDI+IFI is a unique group which has not been highlighted in other studies. Though the numbers are small (n=3) but this has not been forthcoming in any other studies.
At fever onset the median PCT was highest in this group but it was not statistically