The most often utilized technique for treating and preventing severe hyperbilirubinemia is PT [14]. Ultraviolet (UV) light exposure begins a complicated cascade of events that results in the immune system being downregulated. Numerous immune mediators such as IL-1, IL-6, IL-10, and TNF-α are released by the immune system of the skin to support the systemic immunologic response [14].
Our results showed a statistically significant decrease in hemoglobin (Hb) after PT. This agrees with Saber et al. [14], where Hb levels were significantly lowered after PT. Also, in Beken et al. [15] study, Hb counts were lower after PT. Furthermore, our results were in line with Can et al. [16], who demonstrated that the total serum bilirubin, hemoglobin, hematocrit, leukocyte, and neutrophil counts were significantly lowered.
While, in El Mashad GM et al. [17] study, there was an insignificant difference between the cases according to hemoglobin level before and after PT.
We also found an insignificant difference in the total leucocytic count before and after PT. This comes in agreement with Saber et al. [14], where a comparison of WBCs count in patients before and after PT showed a lack to show any difference. Also, Kurt et al. [18] stated that WBCs did not reveal any essential changes.
Against our study, Jahanshahifard et al. [19] showed that PT in term neonates could raise peripheral WBC count. Also, in Abdelhakeem et al. [20] study, they observed a significant increase in WBCs after 36 h and after 72 h, then started to decrease after stop of PT on the 7th day. As shown by Can et al. [16] non-significant change in lymphocyte and basophil counts was observed after PT in our study too.
In our finding, there was a decrease in platelet count after PT than before PT. This agrees with Sarkar et al. [21], who demonstrated that platelet count was significantly lower after PT than before. In contrast, Abdel mohsen et al. [22] demonstrated that platelet count was significantly higher after PT than before PT. In our finding, there was a decrease in platelet count after PT than before PT.
We found a significant increase in the absolute and relative eosinophil count after PT. Our finding was in line with the eosinophil count was significantly elevated (p = 0.01) after PT. In Beken et al. [15] and El Mashad GM et al. [17] eosinophil levels were also increased after PT for 48–72 h. Altuntas et al. [23] also found that PT was linked with a significant increase in eosinophil.
In the current study, there was a significant increase in tumor necrosis factor α (TNF-α) after PT. This result is in line with Saber et al. [14], who found serum TNF-α levels significantly elevated after exposure to PT and this means the strong effect of PT on TNF-α serum levels.
Our finding agreed with Neam et al. [1], who found that serum TNF-α levels significantly increased after exposure to PT for 72 h when compared to values before PT, demonstrating the influence of PT on serum levels of TNF-α.
Also, Jahanshahifard et al. [19] stated that exposure to PT in the treatment of neonates with hyperbilirubinemia might influence cytokine production and release from the peripheral immune system, as it increases serum TNF-α. Kurt et al. [18] stated that usage of PT in neonates with jaundice as a treatment affects the function of the immune system in newborns through alterations in TNF-α production. Narbutt et al. [24] stated that exposure of healthy term neonates to repeated doses of UV radiations shows a significant increase in serum level of TNF-α. Serum TNF-α and eosinophil count increased after treatment of neonatal hyperbilirubinemia by PT which indicates an allergic response to PT in neonates.
In our finding, there was highly significant positive correlation between TSB and eosinophil % before PT. In agreement with our results, Can et al. [16] found that statistically significant positive correlation between bilirubin and eosinophil levels before PT. Further studies are needed to investigate the relationship between PT and childhood eczema, rhinitis, and early-onset wheezing or allergic sensitization.
Limitation of the study
The study was a single center with insufficient sample size, and the study did not include the long-term complication of the PT on neonates with hyperbilirubinemia.
So, we recommended that further studies on large scale to evaluate the allergic response of PT also doing the same work in preterm infants for generalization of the results.
Infants receiving PT should be followed up with care to prevent the development of side effects of PT as allergic reactions.