The application value of mean red blood cell volume and red blood cell volume distribution width combined with total serum bilirubin in the early screening of neonatal hemolytic disease

Hemolytic disease of the newborn (HDN) is caused by the immunologic incompatibility of the blood type of the mother and child, which can result in anemia and jaundice in children. If it cannot be treated effectively in time, severe jaundice can be secondary to bilirubin encephalopathy, which can cause severe nervous system damage [1, 2]. As such, we must pay more attention to the early screening of HDN, which is very important for guiding the treatment plan and improving the prognosis of the patient. The hemolytic nature of HDN is described as the abnormal destruction and decomposition of red blood cells, causing heterogeneous manifestations such as abnormal red blood cell volume and morphology. The application of red blood cell morphology in the identification of hemolytic jaundice has been reported in the literature [3, 4]. Mean corpuscular volume (MCV) and red blood cell volume distribution width (RDW), the results of which are more objective and accurate than morphology, are commonly used parameters related to red blood cell volume. At present, the antibody screening of pregnant women is not routinely carried out. Total serum bilirubin (TSB) is routinely monitored among newborns in clinical practice. According to the changes in its level, three hemolysis tests are carried out to confirm HDN, but the tests take a long time; If the TSB level is low, HDN diagnosis may be missed. This study aims to explore the early changes of MCV and RDW in children with HDN, combined with bilirubin detection, to improve the efficiency of HDN diagnosis during hospitalization and reduce readmission rate.

The bilirubin level of pathological jaundice is high and lasts for a long time. Therefore, it is very important to identify the cause of jaundice early and intervene in time to avoid severe hyperbilirubinemia. In our study, it can also be seen that the bilirubin level of the children gradually increased after birth. The late TSB of the children in the HDN and non-HDN groups was higher than that in the early stage, and there was no difference between the two groups in the late TSB. These findings indicate that as children age, high bilirubin levels are no longer conducive to identifying the cause of jaundice. However, the early stage HDN group had a higher TSB than the non-HDN group (230.7 vs. 152.4), indicating that the risk of hyperbilirubinemia in the HDN group was higher than that of the non-HDN group. Previous literature has also shown that HDN is a risk factor for neonatal hyperbilirubinemia [8]. In addition, the study found that the detection rate of HDN was higher than that of other causes of jaundice (63.4% vs. 32.8%) in the early stage, indicating that the HDN detection rate decreases with increasing age. Moreover, it was found that the incidence of HDN in females was higher than that of male children, which was consistent with the reported [9, 10].

This shows that early TSB monitoring in children with jaundice is not only beneficial for screening the possible cause but also for treatment. The current guidelines recommend measuring neonatal TSB within 24 h after birth, and carrying out follow-up laboratory tests based on changes in the TSB [11]. In China, the peak period of jaundice in term infants appears between the fourth and sixth day of life. With the improvement of medical standards, hospital stay among newborns has shortened. The peak period of jaundice is often after hospital discharge; however, there is a lack of follow-up examinations. Lack of awareness of the hazards of jaundice and insufficient attention to it, are important reasons for severe hyperbilirubinemia and even bilirubin encephalopathy [12, 13]. At present, there have been researches on the use of smartphone applications for bilirubin screening, supplementing TSB monitoring after discharge from the hospital [14]. This research focuses on the routine screening of TSB, combined with simple indicators, such as MCV and RDW, to improve the diagnostic efficiency of HDN during neonatal hospitalization (1–3 days of age), reducing the readmission rate and risk of hyperbilirubinemia.

Routine blood tests are one of the most basic blood tests for the monitoring and treatment of admitted children. A large number of blood cell-related parameters can be obtained, which is of great significance for the differential diagnosis of many diseases [15, 16]. Among these, MCV is a parameter that reflects the volume of peripheral RBCs. It has been reported that in ABO-HDN, the peripheral blood broken cell index and blood smear spherical red blood cell ratio are relatively high [17]. In this study, the children in the HDN group and the non-HDN group had MCV in the early stage greater than that in the late stage, and the MCV gradually decreased with the progression of the jaundice course, which was contrary to the development process of TSB. In contrast to TSB, the MCV of the HDN group was higher than that of the non-HDN group in both the early and late stages (99.6vs96.3, 96.4vs93.8, respectively). It was also found that the higher the early MCV, the higher the probability that the child was diagnosed with HDN (R² = 0.229), and the correlation with HDN was higher than that of previously reported indicators (such as reticulocytes and lactate dehydrogenase) [18]. In particular, when the early MCV > 96.35fL

RDW is a parameter that reflects the volume heterogeneity of peripheral RBCs. It is automatically generated after the red blood cell volume is detected using a blood analyzer. Compared with observing red blood cells on a blood smear with the naked eye, it can more objectively reflect the degree of unequal size of red blood cells. Additionally, the instrument counts two parameters: RDW-CV and RDW-SD. In this study, the multivariate binary logistic analysis showed that early RDW-CV was an independent factor that improves the detection rate of HDN. Early-stage measurement of RDW-CV was greater than that of the late stage, and it decreased with the progression of the jaundice course, which is also opposite to the development course of the TSB. Similar to the TSB, there was no difference in the late detection value of RDW-CV between the HDN and non-HDN groups, but the early detection value was higher in the HDN group (16.8vs15.7). The study found that the higher the early RDW-CV, the higher the probability that the child will be diagnosed with HDN (R² = 0.36), and the correlation with HDN was better than that of previously reported indicators [18], especially when the early RDW-CV > 16.05% (OR _adjust = 3.972), HDN should be screened.

MCV and RDW are traditionally used in the differential diagnosis and treatment of anemia. Recent studies have also found that MCV and RDW are related to the infection process [19‐21], and RDW was found to be related to a variety of diseases [22‐24], such as cardiovascular disease, diabetes, kidney disease, etc. In this study, the TSB, MCV and RDW-CV were independent factors that increased the early detection rate of HDN. The early measurement of MCV and RDW-CV was valuable for improving the detection rate of HDN. The AUC for each index was greater than 0.600. Combined with the TSB (with an AUC of 0.729) for screening HDN, the AUC was 0.841. Joint monitoring could increase the detection rate of early HDN compared with a single index. Although the specificity of each index was not high, the sensitivity was good, and the early value was increased. Contrary to the developmental process of TSB, they complement each other for observation. Therefore, MCV and RDW-CV can be used as early screening indicators, and combined with TSB, has application value in the early screening of the cause of jaundice.

In the study, it was also found that in the group with MCV > 96.35fL or RDW-CV > 16.05%, the probability of anemia in children was higher (20.3%vs36.5%, 22.0%vs36.5%, respectively). A few children underwent emergency blood transfusion to treat anemia symptoms, and then samples were taken for three hemolysis experiments. This will affect the results of the experiments due to the consumption of blood group antibodies, which may cause missed HDN detection. There are not many of such cases in this study, and there is still a lack of sufficient observation with regards to this. We can pay more attention to the dual role of MCV and RDW-CV in blood transfusion guidance and HDN screening in such children. Additionally, the reticulocyte count often rises in hemolytic conditions. Reticulocytes are larger than mature RBC, thereby elevating the MCV, and the mixture of reticulocytes with mature RBC elevates the RDW. Therefore, reticulocytosis should continue to be observed as the underlying mechanism for the observed MCV and RDW elevations. This study did not include cases diagnosed with suspected HDN and those with multiple causes of jaundice, such as HDN with premature delivery, infection, G6PD deficiency, etc. Thus, this study can continue to expand the data used to improve the comparison.

In summary, MCV and RDW-CV can be used as early screening indicators, combined with TSB, to improve the early detection rate of HDN, and guide targeted treatment of HDN. This is as to be timely and effective in reducing the level of bilirubin, there by reducing the readmission rate and risk of hyperbilirubinemia.