Eosinopenia As a Marker of Sepsis in Intensive Care Unit Patients in

: Background: Sepsis is one of the most common causes of mortality and morbidity in the intensive care unit (ICU). Objective: This study was done to evaluate eosinopenia as a marker of sepsis in intensive care unit patients. Materials and Methods: This cross sectional study was carried out in the Department of Clinical Pathology, Bangabandhu Sheikh Mujib Medical University, Dhaka . AEC was done by automated cell counter and rechecked manually microscopically. Observations and Results: In this study 74 suspected case of sepsis were enrolled from intensive care unit, BSMMU, Dhaka. To evaluate the usefulness of AEC for predicting significant sepsis the area under the ROC curve was analyzed. The area under ROC curve was 0.765 in current study. At the cut off valve of AEC < 40 cell/cu mm, the sensitivity and specificity of AEC for diagnosis of sepsis was 72.5% and 61.8% respectively. Conclusion: This present data revealed that decreased absolute eosinophil count was significantly associated with sepsis. So eosinopenia may be a reliable marker for early diagnosis of sepsis.


Introduction:
Sepsis is one of most common causes of mortality and morbidity in the intensive care unit 1 . Despite continuing advances in diagnosis and treatment, sepsis remains one of the important causes of higher mortality and morbidity. Early diagnosis of sepsis plays an integral role in the morbidity and mortality of patients admitted to the intensive care unit 2 .
Sepsis is a systemic inflammatory response to infection, manifested by two or more of the following condition as a result of infection: Temperature >38 0 c or < 36 0 c, Heart rate >90 beats/ min, Respiratory rate > 20 breaths/min and white cell count >12,000/cu mm,<4000/cu mm, or >10% immature (band) forms 1,3 .
Sepsis was documented more than 35% of patients during their ICU stay 4 . The hospital mortality ranged from 16.9% for non-infected patients to 53.6% for patients who had infection at ICU. An estimated 7,50,000 cases of sepsis occur annually in the United States and the mortality rate is about 30%. The incidence will increase by 1.5 per year 5 .
Normal eosinophil count is 40-400 cells/cu mm of blood 6 . Eosinopenia refers to a reduction in the normal number of circulating eosinophils 7 . The level of eosinophils is normally tightly regulated 1 . Eosinophil production is regulated by IL-3, IL-5 and granulocyte macrophage colony stimulating factor (GM-CSF). Without these cytokines, eosinophil can not survive. These cytokines are not significantly activated in patients with sepsis. It is believed to be main mechanism of eosinopenia is sepsis 8 . Eosinopenia during infection is also enhanced by chemotactic substance such as C5a 9 . This substance causes migration of eosinophils into the inflammatory site 10 . Chemotactic factor (C 5a) causes a brief non specific granulocytopenia followed by a prolong eosinopenic-neutrophilic response. So eosinopenia caused by migration of these cells from the vascular space, inhibition of bone marrow release and eventual decrease in marrow production 11 .
Sepsis and non-infectious systemic inflammatory response syndrome (SIRS) produce very similar clinical feature 2 . Therapy and outcome differ greatly between patient with and those without sepsis. The widespread use of antibiotics for all such patients is likely to increase antibiotic resistance and toxicity 12 . The definitive diagnosis of sepsis is made by a positive culture, which requires a minimum of 48-72 hours 13 . As the culture procedure is costly and longer time required, other tests in the diagnosis of sepsis are required 4 . Several markers like C-reactive protein, procalcitonin, lactate, Interleukin-1 (IL-1), Inter leukin-6 (IL-6), Tumor necroting factor (TNF), triggering receptor expressed on myeloid cells-1 (TREM-1) etc have been reported to predict sepsis 9 . Most of these markers are expensive, not easily accessible to clinicians, less sensitive and not ideal for early diagnosis of sepsis. Among these markers, eosinopenia shows more diagnostic sensitivity and specificity. Among these markers blood eosinophil count is simple, easy, quick, less expensive and reliable marker of sepsis 9 . It is a part of complete blood count which is done as routine laboratory test. It reduces widespread use of antibiotic, mortality and sepsis related complications and shorten the hospital stay. So this study was carried out to evaluate the diagnostic sensitivity of eosinopenia for detection of sepsis in ICU patients.

Materials and methods:
This cross sectional study was carried out at the Department of Clinical Pathology in collaboration with Department of Anesthesia, Analgesia and Intensive care Medicine and Department of Microbiology and Immunology, Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka from March 2012 to February 2013. Study population was 74 patients selected from intensive care unit, BSMMU, according to inclusion criteria. Suspected cases of sepsis and adult age group were included in the study. Prior to the commencement of this study, the research protocol was approved by the Institutional Review Board (IRB) of BSMMU, Dhaka. 2ml blood was collected for CBC including AEC which was done by automated cell counter and rechecked manually microscopically. Single set of culture was done for each patients. All data were recorded systematically in a preform data collection sheet and expressed as mean ± standard deviation (SD), t-test, Z test, Chi-square test. ROC curve and the respective area under curves was calculated for eosinophils. Sensitivity, specificity were calculated at the best cut off value. Statistical analysis was done by using statistical package for social science SPSS 17.0. P value <0.05 was considered as significant.

Result:
In this study, 74 patients were divided into two group according to blood culture findings. Out of 74 patients, 34 patients were considered as proven sepsis by blood culture as infection group. The rest 40 patients were considered by blood culture as non infection group. Suspected case of sepsis and adult age group were included in the study. The mean ± SD of AEC was found 18.3±11.4 cells/cu mm in infection group and 145.0±57.7 cells/cu mm in non-infection group. In infection group AEC was lower than non-infection group. The result was statistically highly significant (p<0.001). To evaluate the usefulness of AEC for predicting significant infection the area under the ROC curve was analyzed. The area under the ROC curve was 0.765 in current study. In receiver-operating characteristic (ROC) curve the cut-off value of AEC < 40 cell/cu mm. At this cut-off value the sensitivity and specificity of AEC in diagnosing infection were found to be 72.5% and 61.8% respectively. These findings were statistically significant (P < 0.001).

Receiver-operating characteristic (ROC) curve of Absolute Eosinophil Count (AEC) for prediction of infection
The area under the receiver-operating characteristic (ROC) curves for the infection predictors is depicted in the following table.
Based on the ROC curves AEC had the best area under curve. ROC were constructed using AEC of the patients with infection, which gave a AEC cut off value of (<40 cells/cu mm) as the value with a best combination of sensitivity and specificity for infection. At this AEC cut-off value of <40 cells/cu mm, the sensitivity and specificity of AEC in infection was found to be 72.5% and 61.8%, respectively (Table 1I and Fig  2). These findings were statistically significant (P< 0.001). The level of eosinophils in the body is normally tightly regulated 1 . Eosinophil production is regulated by IL-3, IL-5 and granulocyte macrophage colony stimulating factor. Without these cytokines, eosinophil can not survive. These cytokines are not significantly activated in patients with sepsis. It is believed to be main mechanism of eosinopenia in sepsis 8 .

Conclusion:
The result from our study support that AEC is significantly lower in patients with sepsis. Eosinopenia may be a useful marker to distinguish the infected from non infected patients. An early diagnosis of sepsis is made by absolute eosinophil count that can be obtained from routine laboratory test (Complete blood Count) which is simple, quick, cost effective and readily available. In our study eosinopenia provide an effective guideline to make decision regarding judicious use of antibiotic therapy which will be life saving and minimize the risk of emergence of resistant organism due to misuse of antibiotics.