الفهرس 
Chapter (1) :Anatomy of Respiratory SystemOnly 14 pages are availabe for public view
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Abstract
Acute respiratory tract infections (ARIs) are the most common reason for children to visit physicians and the major cause of mortality and morbidity in children < 5 years of age . Studies have revealed that ARIs account for 30-60% of visits to health providing centers and 30-40% of admissions to pediatric hospitals thus incurring huge expenses on the health care system of a country. In developing countries, 30-50%childhood deaths are caused by ARI, particularly pneumonia Procalcitonin (PCT),with molecular mass of 14.5 KDa, is the 116 amino acid polypeptide precursor of calcitonin ,a calcium regulatoryhormone .Production is governed by Calc-1 gene, located on chromosome 11.Calc-1 codes for preprocalcitonin which undergoes proteolytic cleavage of its signal sequence to produce PCT. Serum Procalcitonin (PCT) levels are of interest as a biomarker in patients with respiratory tract infections for several reasons. Serum PCT levels are elevated in patients with bacterial pneumonia and septic shock . To the contrary, data suggest that serum PCT levels are not elevated in patients with viral respiratory tract infection unless there is a superimposed or coincident bacterial infection . Therefore, serum PCT levels potentially can assist in clinical decisions regarding whether patients with respiratory tract infection would benefit from empirical antibiotic therapy. This study was designed to evaluate serum level of procalcitonin in cases of lower respiratory tract infections to distinguish between bacterial and viral LRTIs. The present study was conducted on 55 patients diagnosed clinically as lower respiratory tract infections (pneumonia and bronchiolitis) and supported by radiological , laboratory and microbiological investigations. The patients were recruited from El Menoufiya university hospital department of pediatrics. They were divided into 3 groups, group I bacterial ) include 15 patients who were diagnosed clinically ,laboratory and microbiologicaly as pneumonia .Group II (viral) include 30 patients who were diagnosed clinically, laboratory and microbilogically as bronchiolitis and the third group (control) include 10 apparently health children matched for age ,sex and socioeconomic status. All patients and controls included in the study were subjected to the following : 1- Full clinical evaluation including : Detailed history taking stressing on presence or absence of fever, cough, shortness of breath , wheezes and grunting. Thorough physical examination lying stress on temperature, respiratory rate as part of general examination .Chest examination as part of local examination. 2- Laboratory investigations: For patients only :CBC by differential scanning calorimeter ,ESR by westergren method ,CRP by Abbott Aeroset method. For patients and control: serum PCT level by ELISA 3- Radiological investigation: chest X -ray for patients only. 4- Microbiological investigation: sputum culture for patients only. Regarding age the results of our study revealed significant difference between group I and control ,group I and group II while no significant difference between group II and control .Gender ,consanguinity and socioeconomic status were not significantly different between studied groups. As regard clinical data there is high significant difference between groupI& group II regarding wheezes, crepitations, II respiratory distress running eye ,running nose and sneezing being high in group(II). While there is no significant difference between group (I) and group (II) regarding high and low grade fever, cough, shortness of breath ,cyanosis ,grade II&III respiratory distress. As for vital signs data they were significantly different between studied groups. Regarding Hb level, RBC count, platelet count there were no statistical significant difference among group I&II .However WBCs & granulocytes were higher in group I and lymphocytes were higher in group II. As regard sputum culture streptococcus pneumoniae was the most frequent growth in the sputum culture in group I. Chest X-ray finding shows that the incidence of broncho& lobar opacities werehigher in group I while interstitial opacities &hypertranclucency were higher in group II. As regard CRP&ESR(1st hour and 2nd hour) there were higher in group I than group II. Regarding serum level of PCT , our study revealed that it was significantly higher in group I than group II and control.Regarding serum level of PCT , our study revealed that it was significantly higher in group I than group II and control. In our study there was significant positive correlation between serum PCT and CRP& ESR in group I. Our results concluded that PCT is areliable marker for distinguishing between bacterial or viral origin LRTIs.