Background: Bladder cancer is the second most common urological malignancy. Cystoscopy is the “gold standard” for the detection of bladder cancer, but is invasive and relatively expensive. This study aimed to investigate the sensitivity and specificity of serum levels of free and total sialic acids as tumor markers in the diagnosis of bladder cancer.

Materials and Methods: In this study, the diagnostic value of blood samples collected from 58 patients with bladder cancer and 60 normal subjects were evaluated. The spectrophotometrical Aminoff's method was used for measuring serum levels of free and total sialic acids. After comparing the mean values for the mentioned parameters, ROC curve was used to calculate the sensitivity and specificity and other diagnostic values of markers.

Results: The mean values for total sialic acid and free sialic acid were higher in cancer patients than in normal healthy controls (P<0.001). The sensitivity and specificity of total sialic acid at the cut-off point of 48.75 mg/dL were 91% and 82%, respectively and also the sensitivity and specificity of free sialic acid at the cut-off point of 0.708 mg/dL were 81% and 80%, respectively. Moreover, a positive correlation was seen between the serum levels of total, free sialic acids and stage or grade of the tumor.

Conclusion: Our results revealed that the measurement of serum levels of these parameters using some simple, non-invasive, inexpensive, and reproducible tests can diagnose the bladder cancer and provide important clinical findings on the extent of the malignancy and also reduce the number of cyctoscopies.