Design and subjects
A retrospective cohort study was performed in one of the largest tertiary A-level hospitals in Sichuan Province, China, in which all admissions between the period of 1 January 2017 and 31 December 2018 were included, with the exception of inpatients who were hospitalized within 2 calendar days.
Cohorts
This study included 4 cohorts, including cohort-RBCs, cohort-FFPs, cohort-cryo and cohort-platelets.
Cohort-RBCs: Inpatients were transfused with RBCs during the study but did not transfuse any other blood product.
Cohort-FFPs: Inpatients were transfused with FFPs during the study but did not transfuse any other blood product.
Cohort-cryo: Inpatients were transfused with cryoprecitation during the study but did not transfuse any other blood product.
Cohort-platelets: Inpatients were transfused with platelets during the study but did not transfuse any other blood product.
Outcomes
The presence of healthcare-associated infection was the primary outcome of this study.
The diagnostic criteria were the "HAIs Diagnostic Criteria" issued by the Ministry of Health of the People's Republic of China in 2001 [14]. HAIs were defined as infections acquired by inpatients in hospitals, which included infections that occurred during hospitalization and those acquired in hospitals but occurred after discharge. The criteria excluded infections that occurred prior to or at the time of admission.
All reported cases of HAIs were examined by three infectious disease specialists to ensure accurate identification of the infected cases.
Risk factors for HAI
Potential confounders were selected based on previous literature [15-18], and included age, gender, principal diagnosis, diabetes, hypertension (systolic blood pressure ≥ 140 mmHg and/or diastolic blood pressure ≥ 90 mmHg [19]), chronic obstructive pulmonary disease, hemodialysis, venous catheterization, mechanical ventilation, urinary catheterization, tracheotomy, surgery, ICU admission now or in the past and community infections.
Data collection
Data was obtained from 3 information systems, including inpatient records system, blood transfusion records system and HAI management information system.
Only ABT given before the onset of HAI were evaluated. Per blood product, a qualitative variable (transfusion yes or no), and 2 quantitative variables (amount of product in units and frequency of transfusion) were generated.
Statistical analysis
We analyzed the dose-response relationship between blood transfusion components and HAIs using a two-step approach described below. First, we evaluated risk factors associated with HAIs. A logistic regression model with HAIs as the dependent variable was used, and the association between HAIs and RBCs, FFPs, cryoprecitation or platelets were analyzed. Second, Cox regression was performed with the same independent variables as in step 1, and restricted cubic spline regression was used to visualize the hazard of HAI per transfusion product.
Data were summarized using the mean and standard deviation (SD) for normally distributed variables and the median and inter-quartile range (IQR) for non-normally distributed variables. Categorical variables were expressed in absolute numbers and percentages. Statistical analysis of the data was performed using STATA 12.0. Binary outcomes were tested using the χ2 test, and continuous data were compared using Mann–Whitney test or the T-test. P values below 0.05 were considered significant.