The Evaluation of Urine Macrophage Migration Inhibitory Factor (MIF) in Children with Urinary Tract Infection: A Possible Predictor of Acute Pyelonephritis

Urinary tract infection is the second most common bacterial infection amongst children which could lead to renal scars. It is supposed that during renal inflammation and all types of renal injury, macrophages infiltrate renal parenchyma, whereas their number is directly correlated with the intensity of inflammation. In fact, macrophage migration inhibitory factor (MIF) is widely expressed and secreted in response to inflammatory stimuli, and plays an important role in renal tissue injury. Yet, the role of MIF was not evaluated in patients with pyelonephritis in any studies. Therefore, the aim of our study was to compare urinary excretion of MIF in acute pyelonephritis, acute cystitis and also control group in order to find a non-invasive and sensitive method to differentiate between them. In this analytical cross-sectional study 31 children with urinary tract infection (25 patients with acute pyelonephritis, 8 patients with acute cystitis) and 40 healthy children were recruited. Sterile midstream urine samples were taken to measure MIF concentration in all patients and healthy individuals as well. Urine MIF concentration was determined by ELISA and corrected for urine creatinine. The data were analyzed using SPSS 13 software. Independent t-test, One Way ANOVA, correlation and Receiver Operating Curve (ROC) analysis were performed. The mean ratio of urine MIF/Cr was 66.14(SEM=23.78) pg/µmol creatinine in acute pyelonephritis patients, 1.58 (SEM=0.59) pg/µmol creatinine in acute cystitis patients and 1.85 (SEM=0.35) pg/µmol creatinine in healthy individuals. It was significantly higher in pyelonephritis patients than the ones in acute cystitis patients (P<0.001) and control group (P<0.001), respectively. ROC analysis demonstrated that urine MIF/Cr ratio could Pejuhandeh Vol.13, No 64, 2008 3 be considered as a potentially useful index to detect acute pyelonephritis among both healthy condition [P<0.001, Area under curve (AUC) = 0.959] and acute cystitis [P<0.001, AUC = 0.960]. Also the optimal cut-point of 5.39 pg/µmol creatinine and 4.90 pg/µmol creatinine for urine MIF/Cr ratio could potentially distinguish acute pyelonephritis patients from healthy individuals and the ones with acute cystitis, respectively. To the best of our knowledge, urine MIF level of children with cystitis, pyelonephritis and control group were compared with each other for the first time in our study. We showed that the urine MIF/Cr ratio was not increased in acute cystitis. Whereas, rising of this ratio in patients with acute pyelonephritis was remarkable. We also revealed that urine MIF/Cr ratio is a sensitive test for differentiation of acute cystitis from pyelonephritis.