The Ethics Committee of Second Hospital of Hebei Medical University approved this prospective study. All patients signed the written informed consent and participated voluntarily.
Patients
All patients undergoing PCI admitted to our hospital from 1 January 2016 to 31 December 2016 were prospectively enrolled in this study. Patients with any of the following were excluded: allergic to contrast media; contrast media exposure within 2 days prior to PCI; emergency PCI; chronic kidney disease or post-transplantation; malignant tumor; autoimmune disease; recent surgery, or a history of trauma within 1 month; fever or infection within 1 month diagnosed according to the infective symptoms (salivation, cough), physical examination, laboratory tests, or chest X-ray or CT image; or acute or chronic inflammatory diseases.
The final study population comprised 343 patients (247 men and 96 women). Ages ranged from 27 to 77 years, with a mean age 57.86 ± 9.16 years. The average age of the men and women were 56.6 ± 9.3 years and 61.1 ± 7.9 years, respectively.
All patients received continuous hydration at 1 mL·kg− 1·h− 1 (about 2000 mL of normal saline), from 4 h before PCI to 24 h after PCI, and a dose of furosemide (20 mg) was given immediately after PCI.
For this analysis, the patients were compared as being with or without CIN after PCI (i.e., CIN or non-CIN). CIN was defined as an increase of preoperative serum creatinine by 25%, or total ≥ 44.2 μmol/L (0.5 mg/dL), within 48 to 72 h after intravenous injection of contrast media [13]. Serum creatinine was tested before and at 48 h after the procedure.
Data collection
Patients’ baseline characteristics and medication histories were collected. Routine laboratory data before and after the PCI procedures included routine tests of blood, urine, and stool, liver and kidney function, serum lipids and glucose, brain natriuretic peptide, myocardial enzyme, CRP, and PCT. All the blood variables were measured using an autoanalyzer (Hitachi 747; Hitachi, Tokyo, Japan) at our central laboratory.
Testing of CRP and PCT
Venous blood specimens were centrifuged at 200×g for 10 min, and serum was tested for high-sensitive CRP (hs-CRP) and PCT. The levels of hs-CRP were measured using a commercial, high-sensitivity nephelometric assay (Cias Latex CRP-H, Kanto Chemical, Tokyo, Japan). PCT was tested using a solid-phase sandwich enzyme-linked immunosorbent assay (PCT kit, SEA689Hu, Chinese and American Technology, China).
PCT and hs-CRP were each differentiated as low or high according to the median cutoffs, 97.47 pg/mL and 2.1 mg/L, respectively. Because CRP and PCT are biomarkers of inflammation, the patients were also stratified into low-, medium-, or high-inflammation groups based on their combined CRP and PCT status. Specifically, low inflammation was defined as low CRP and low PCT. Medium inflammation was considered the combination low CRP and high PCT, or high CRP and low PCT. In the high-inflammation group, both CRP and PCT were high.
Statistical methods
All statistical analysis was performed with SPSS for Windows (version 18, SPSS, Chicago, IL, USA) and Medcalc software. For normally distributed data, continuous variables are shown as mean ± standard deviation. For comparisons between the CIN and non-CIN groups, the independent-sample t-test was used. Otherwise, the median and interquartile range (25–75%) values are displayed, and non-parametric tests were conducted. Categorical variables are shown as number and percentage (%) and compared using the chi-squared test. The software program MedCalc was utilized to measure the receiver operating curve (ROC) for determining the differences between the area under ROC curve (AUC) of each biomarker for distinguishing between CIN and non-CIN patients. Multiple logistic regression analysis was used to identify independent risk factors of CIN. A statistical difference was defined as P < 0.05.