Ichthyophthiriasis (white spot disease) is known as one of the most commonly parasites found in overcrowded pools. Cystatin c is known to be the most valuable serum biomarker in determining renal function. Gelsolin is known as an actin-binding protein that eliminates and minimizes blood actin. Regulatory role of hepcidin in iron metabolism and reducing the amount of iron available to microbes plays its antimicrobial role and sphingosine 1 phosphate is able to increase and stimulate antimicrobial activity in host cells. This study was conducted in the summer of 2012 in Urmia, where a number of rainbow trout were collected from eight crowded aquaculture farms. Blood samples were taken from the tail vein of all fish and poured into tubes containing EDTA and significance of the analyzes was set at the level (P<0.01). According to the results, cystatin c, hepcidin and sphingosine 1 phosphate in infected fish were significantly increased compared to healthy fish, while the gelsolin level was significantly reduced. In conclusion, based on ROC statistical analysis, `hepcidin` has high sensitivity (88.6%) than other ones and it means that, hepcidin may utilize as `Possible Potential Diagnostic Biomarker` in rainbow trout Ichthyophthiriasis.