Neonatal sepsis is manifested by bacteremia and clinical manifestations due to microorganism invasion and their toxins. Neonatal sepsis diagnosis should include infection establishment with a systemic illness in which non-infectious explanations for patho-physiologic abnormality are excluded .
Accurate diagnosis is made by blood culture which is a time-consuming method. For this cause, neonatologists tested a number of other biochemical markers for accurate diagnosis of sepsis in the shortest time as red cell distribution width (RDW) which is an early cheap and available biomarker for diagnosis of neonatal sepsis .
In our study, the mean RDW was highly significantly higher in cases compared to controls (16.65 ± 4.28, 11.13 ± 0.62, respectively) (P = 0.000); this finding is in agreement with Jianping et al.  who reported significant statistical difference regarding RDW value between cases of sepsis and controls (19.61 ± 1.48, 16.04 ± 1.25, respectively) (P-value = 0.0001). Increased RDW may comprehensively reflect the pathophysiological mechanisms in the occurrence and development of sepsis as inflammation may cause an increase of neuro-hormone and endocrine hormone in the body including noradrenaline, angiotensin 1, and other angiotensin levels. These neurotransmitters can stimulate RBC proliferation by promoting the generation of erythropoietin (EPO) to result in an RDW increase ; inflammatory factors may affect the bone marrow hemopoietic system and iron metabolism to cause RDW increase . RDW increase may indicate unstable cytomembrane which may cause multiple organ dysfunctions that make the patients’ condition deteriorate, thus leading to poor prognosis and increased mortality. Studies found that the materials providing the nutrition to the body and cell, such as blood cholesterol, albumin, and others, are lacking while RDW increases. Therefore, increased RDW may reflect the cell membrane instability due to the lack of cholesterol and other substances in the body . Severe sepsis/septic shock may be combined with multiple organ dysfunction.
Our study revealed a highly statistically significant difference regarding Hb levels between cases and controls (14.36 ± 2.58, 17.88 ± 2.13, respectively) (P-value = 0.000); there were 20 cases with low Hb levels (20%) and 80 cases (80%) with normal Hb levels while controls (100%) had normal Hb level; meanwhile, RDW showed a non-statistical significant increase in the group of sepsis with normal Hb level than the other groups with low Hb level (16.81 ± 4.32, 16.01 ± 4.20, respectively) (P-value = 0.45). This may point to the multifactorial causes of low HB % other than sepsis, and the increase of RDW in sepsis cases in spite of normal Hb level proves that the RDW can be used as an early indicator for the diagnosis of sepsis. The current study showed a highly statistically significant relation regarding leukocytic count 20% of cases had leukopenia while 80% of cases had leukocytosis with a shift to the left; meanwhile, all controls (100%) had normal leukocytic count (P-value = 0.000). This finding is in agreement with the large number of studies that have been performed to evaluate the use of CBC, differential count, and immature to total leukocyte ratio (I:T) for the diagnosis of neonatal sepsis . Saleh et al.  reported that CBC has a poor predictive value, and serial normal values can be used to enhance the prediction that bacterial sepsis is not present.
In this study, 21 of the cases (22%) had sepsis, 31 cases(31%) had severe sepsis, and 48 cases (48%) had septic shock, which reflects the high prevalence of severe sepsis and spotlights the need to diagnose this problem early to minimize its complications and burden on the health system and future development of such patients.
As regards the severity of neonatal sepsis, our study revealed statistically significant differences in the mean HB level, CRP, and RDW between the three groups of sepsis (sepsis, severe sepsis, and septic shock); the mean HB level was higher in the sepsis group than in the severe group and septic shock group (15.54 ± 2.44, 14.90 ± 178, 13.88 ± 2.64, respectively) ( P-value 0.026); meanwhile, CRP was higher in the septic shock group than in the severe sepsis group and sepsis group (61.42 ± 64.29, 13.56 ± 1.57, 7.16 ± 1.43, respectively) (P-value = 0.00), while there were statistically significant differences between the three groups (sepsis, severe sepsis, and septic shock) regarding RDW (15.15 ± 1.65, 16.78 ± 2.01, 17.02 ± 2.02, respectively) (P-value 0.027).
RDW was correlated with the severity of neonatal sepsis; this suggests that septic neonates with RDW ≥ 17% may have a higher severity of illness, and RDW may have value in differentiating between more severe and less severe cases of neonatal sepsis; this finding is in agreement with Kader et al.  who reported that incidence of RDW increase in neonatal sepsis and increased with increasing severity of the disease. He also stated that the mean RDW value in less severe patients was 16.04 ± 0.7, and the mean RDW value in more severe patients was 19.75 ± 1.9.
The mean RDW difference in both groups was statistically significant (P < 0.001) with the severity of the disease higher in severe cases than in mild ones. Saleh et al.  reported that RDW is statistically significantly correlated with the severity of neonatal sepsis.
The current study revealed non-statistical significant differences between 48 deceased neonates in the NICU and 52 neonates discharged from the NICU, regarding HB (13.63 ± 2.21, 15.04 ± 2.72, respectively), but RDW was statistically significant (17.52 ± 2.61, 14.85 ± 2.30, respectively) (P-value 0.02); meanwhile, our statistical analysis revealed that there was highly statistically significant difference in CRP between the discharged group from NICU and the deceased group in the NICU, where the mean of CRP was higher in the deceased group than in the discharged group (77.74 ± 68.68, 12.48 ± 5.08, respectively) (P-value 0.00). Recent studies showed that RDW% can be taken as a “marker” of death in critically ill patients and may be used to predict death risk independently in such patients .