الفهرس 
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Abstract
Ventilator-associated pneumonia is a common nosocomial infection in intensive care units (ICUs) and its results can be listed as high mortality, prolonged intensive care stay, and increased health care cost. Ventilator-associated pneumonia accounts for more than half of all antibiotic use in the ICU. As a result, VAP causes great morbidity and financial consequences. Because of these reasons, early diagnosis and treatment of VAP is crucial. Despite its high incidence, diagnosis is very difficult due to the presence of similar clinical findings in many patients in the intensive care unit. In the multiple patient series, there was a weak correlation found between the clinical diagnosis of pneumonia and true pneumonia, and it was stated that 50% of the patients defined as VAP were not really ill, and 1/3 of the VAP patients could not be identified. RDW is routinely reported in automated complete blood counts. It is a widely available, inexpensive, reflecting the range of the size of the circulating red blood cell. Also, laboratory index used in the differential diagnosis of anemia. It is commonly performed in the assessment of almost all the patients at the time of admission. Any process that releases reticulocytes in the circulation will result in an increase in RDW. Many studies suggest that RDW may also be useful as a biomarker of disease severity and clinical outcomes in critically ill patients. An increased RDW is an independent predictor of all causes of mortality in sepsis, congestive heart failure, and adult critical illness, and has been shown to improve acute physiology scoring for risk prediction in critically ill adults. The pathophysiologic mechanisms underlying the association between RDW and VAP-associated mortality are unclear. However, it is possible that its relationship with inflammation and oxidative states plays a role in VAP-associated mortality. The aim of this study was to evaluate the role of RDW as diagnostic and prognostic marker of ventilatory associated pneumonia (VAP). Primary outcome was accuracy of RDW in VAP diagnosis. Secondary outcomes were correlation between RDW duration of mechanical ventilation and 28th day mortality and comparison between RDW and other inflammatory marker as CRP and procalcitonin. This prospective observational study was conducted from Jan 2019 to Dec 2020 on 106 critically ill mechanically ventilated patients ≥18 age < 60 years old of both sex who admitted to intensive care unit (ICU) in Tanta University Emergency Hospital to evaluate the role of RDW as diagnostic & prognostic marker of ventilator associated pneumonia (VAP). Patients were divided to 31 patients developed VAP and 75 patients didn’t develop VAP. Duration of mechanical ventilation, sputum culture results, ICU stay period, incidence of 28th day morality were recorded. CPIS, APACHE II score, CRP and Procalcitonin, RDW were calculated and measured at 1st, 4th and 7th days after admission. The summary of our results: • The incidence of VAP in this study was 29.25% (31 from 106 case). • At cut-off >16.3, RDW at time of diagnosis can significantly diagnose VAP with 83.87 sensitivity, 61.33 specificity, PPV was 47.3, NPV was 90.2, AUC was 0.818 (P value <0.001). At cut-off >70, CRP at time of diagnosis didn’t significantly diagnose VAP, with sensitivity of 61.29, specificity was 29.33, PPV was 64.7, NPV was 26.4, AUC was 0.572 (P value= 0.238). At cut-off >2.2, procalcitonin at time of diagnosis can significantly diagnose VAP with sensitivity of 80.65, specificity was 72, PPV was 54.3, NPV was 90, AUC was 0.835 (P value <0.001). To diagnose VAP, the comparison between diagnostic accuracy of RDW and procalcitonin were superior to CRP (P <0.001), between diagnostic accuracy of RDW and procalcitonin was insignificant (P = 0.971). • As regard to delta RDW, at cut-off >0.4 can significantly predict VAP at sensitivity was 87.10, specificity was 93.33, PPV was 84.4, NPV was 94.6, AUC was 0.897 and P value was <0.001. As regard to delta CRP, at cut-off >14.3 non-significantly predict VAP at sensitivity was 54.84, specificity was 73.33, PPV was 45.9, NPV was 79.7, AUC was 0.589 and P value was 0.215. As regard to delta procalcitonin, at cut-off >2.5 can significantly predict VAP at sensitivity was 54.84, specificity was 97.33, PPV was 89.5, NPV was 83.9, AUC was 0.748 and P value was <0.001. To predict VAP, the diagnostic accuracy of Delta RDW was superior to Delta CRP and Delta procalcitonin (P = 0.005 and 0.044 respectively) and the comparison between Delta CRP and Delta procalcitonin was insignificant (P = 0.082). • There was a positive moderate significant correlation between RDW at time of diagnosis and duration of MV (r = 0.317, P <0.001) but an insignificant correlation between RDW at time of diagnosis and ICU stay (r = 0.141, P = 0.15). There was a positive mild significant correlation between RDW at time of diagnosis and CPIS (r = 0.247, P =0.04) and between RDW at time of diagnosis and APACHE (r = 0.476, P <0.001). • As regard to RDW at time of diagnosis, at cut-off >16.3 significantly predict mortality with sensitivity of 84.62, specificity was 52.69, PPV was 20, NPV was 96.1, AUC was 0.806 and P value was <0.001. As regard to CRP at time of diagnosis, at cut-off >70 didn’t significantly predict mortality with sensitivity of 53.85, specificity was 33.33, PPV was 83.8, NPV was 10.1, and AUC was 0.557 (P value = 0.552). As regard to procalcitonin at time of diagnosis, at cut-off >2.5 significantly predict mortality with sensitivity of 84.62, specificity was 69.89, PPV was 28.2, NPV was 97, AUC was 0.799 (P value= <0.001). • As regard to delta RDW, at cut-off >0.4 can significantly predict mortality at sensitivity was 84.62, specificity was 77.42, PPV was 34.4, NPV was 97.3, AUC was 0.810 and P value was <0.001. As regard to delta CRP, at cut-off ≤60.1 non-significantly predict mortality at sensitivity was 38.46, specificity was 90.32, PPV was 35.7, NPV was 91.3, AUC was 0.574 and P value was 0.469. As regard to delta procalcitonin, at cut-off >2 can insignificantly predict mortality at sensitivity was 61.54, specificity was 75.27, PPV was 25.8, NPV was 93.3, AUC was 0.665 and P value was 0.085. • RDW at time of diagnosis and Delta RDW were significantly higher in non-survivor group compared to survivors. • Delta RDW was the only independent predictor for mortality (P =0.017).