The present study results showed that PIICS is significantly associated with RBC and PLT transfusions. This result was consistent even after adjusting by propensity score matching. In addition to RBC and PLT transfusion, PIICS was associated with sepsis, surgery, CRP and albumin levels, lymphocyte count, Hb and HbA1c levels, and APACHE II score.
Nakamura et al. reported that age, sex, sepsis, albumin level, lymphocyte count, Hb and HbA1c levels, Cr level, and overt DIC were significantly associated with PIICS [5]. Thus, the results of the present study are consistent with their findings. However, in contrast to the report by Nakamura et al. [5], which summarized the risk factors for patients admitted to emergency ward and ICU regardless of in-hospital or outpatient settings, the present study included patients admitted to the ICU from the tertiary emergency department. The difference in patient cohorts between the two studies may explain the differences in findings. Specifically, the patients in this study were younger and mostly male. Furthermore, the number of patients with sepsis was smaller and most had a higher APACHE II score than those in the study reported by Nakamura et al [5]. In addition, the overt DIC was surprisingly small in this study. Furthermore, a new analysis was conducted regarding blood transfusion, which may have caused the difference in the results.
The onset of PIICS associated with RBC transfusion is primarily because TRIM reduces immunity [11–13]. Second, suppressed immunity leads to increased risk of infection and inflammation after transfusion. Additionally, the association of PLT transfusions with PIICS has been associated with an increased risk of post-transfusion infections [14–17]. However, as reported by Péju et al., it has been suggested that FFP and PLT products may also have an immunosuppressive effect [18], and as identified in this study, PLT administration suppresses immunity, which may have affected the onset of PIICS as there was no association between FFP transfusion and PIICS. However, in FFP, aside from RBC and PLT, there were procedures done in patients with liver failure, such as plasma exchange and infusion, that may have affected our results.
Furthermore, RBC and PLT transfusions were associated with PIICS, suggesting that it would be important to consider transfusion criteria according to various diseases and stages in future studies.
This study has several limitations. First, the characteristics of the patient population may have influenced the results as this was a single-institution retrospective study; thus, the results cannot be generalized. Nevertheless, a relatively large number of samples were collected and analyzed. Second, the effects of confounding factors that were not considered in this study were not removed. Third, patient factors that required RBC transfusion may have influenced the outcome, and the effects were incompletely removed. However, as a countermeasure, propensity score matching analysis was performed. Fourth, there may be cases where the diagnosis of PIICS was inaccurate as there were no data available for day 14; in such cases, we included data from the nearest date.
In conclusion, this is the first study to report an association between RBC and PLT transfusions and PIICS. Our findings have contributed to better understanding the risk factors of PIICS and suggest that physicians should consider the risk of occurrence of PIICS when administering blood transfusions in ICU patients.