حجم متوسط پلاکت (MPV)، عرض توزیع پلاکت (PDW)، تعداد پلاکت پلاکت کریت و (PCT) به عنوان پیش بینی مرگ و میر کودکان در بیمارستان: مطالعه شاهد موردی Mean Platelet Volume (MPV), Platelet Distribution Width (PDW), Platelet Count and Plateletcrit (PCT) as predictors of in-hospital paediatric mortality: a case-control Study.

Introduction In-hospital mortality depends on the severity of the illness at the time of admission1 . Severity of illness scores have been developed to predict the mortality in the Intensive Care Unit (ICU)2 . Scoring systems such as the PSI (Physiologic Stability Index), PRISM score (Pediatric Risk of Mortality), SICK score (Signs of Inflammation that Can Kill) are severity of illness scores used in children2–۵٫ In 2000 Vanderschueren and colleagues showed that thrombocytopenia by itself effectively predicts mortality in adults admitted in ICU and is complementary to different established scoring systems6 . In a case control study of 145 patients with sepsis and 143 controls, Guclu showed that, mean platelet volume (MPV) and platelet distribution width (PDW) were useful in diagnosis of sepsis and patients with PDW of more than 18% have a higher risk of death7 . Thrombocytopenia occurring in critically ill patients is the result of hemodilution, increased platelet consumption, increased platelet destruction (immune mechanisms)8 and increased platelet sequestration9 . Septicemia related destruction of platelets increases production and release into the peripheral blood of larger and younger platelets10. Later, however there may be bone marrow suppression7 .  Platelet volume indices, estimated by automated blood cell analysers, show the changes that accompany the alterations in platelet counts11. Platelet parameters such as MPV and PDW (reflection of the variation of the platelet size in the circulation12 have been routinely available to the clinicians for some time. However their significance in various platelet disorders have only been studied recently7 . Septic rat models have shown that PDW and MPV increase in sepsis with appearance of large and heavy platelets in circulation13. Canine models of endotoxemia have shown that the platelet count and PCT decreased where as MPV and PDW are increased showing that platelet counts are correlated positively with PCT, but correlate negatively with MPV and PDW during early endotoxemia in dogs14. In human studies, Nelson and Kehl reported that in acute infection there was platelet consumption and it was associated with an increase in MPV15. Becchi et al noted that MPV at an early stage of sepsis was important prognostically16. MPV increased during the admission period in those who died, compared to survivors16. In neonates with sepsis, a low platelet count and an increase in MPV has been observed by Guida et al17. Patrick et al demonstrated that neonates with late onset sepsis (bacteremia after 3 days of age) had a dramatic increase in MPV and PDW18. We hypothesize that as the MPV and PDW increase and platelet count and PCT decrease in sick children, intuitively, the ratio of MPV to PCT; MPV to Platelet count, PDW to PCT, PDW to platelet count and the ratio of the product of MPV and PDW to the product of PCT and platelet count could be candidate markers of severity of illness and that these may be useful to predict mortality. To the best of our knowledge these ratios have not been studied in children in this context. We did this preliminary case control study to test this hypothesis. Methods The case control study was done in a tertiary care urban hospital (St. Stephens Hospital) in Delhi – the capital city of India, and the data relates to patients admitted to a tertiary post-graduate teaching hospital between 21/08/2009 to 10/03/2011. The department of Paediatrics is manned by 5 full time consultants and 14 resident doctors 9 of who are fully trained paediatricians working as Senior Registrars and the remaining are Senior House doctors in training for the Diplomate of the National Board in Paediatrics. All children between the ages of one month to fourteen years who died in the hospital were included. Controls were children of matching age (± one year except in infants where they were matched to within one month of the cases) admitted contemporaneously and who survived hospital stay. Forty events (deaths) were examined. Table 1 shows the primary system involved that necessitated hospitalization.