Is there a relation between urinary interleukin-6 levels and symptoms before and after intra-vesical glycosaminoglycan substitution therapy in patients with bladder pain syndrome/interstitial cystitis?

Urinary interleukin-6 (IL-6) has been proposed as a sensitive and specific inflammatory marker in bladder pain syndrome/interstitial cystitis (BPS/IC). We therefore investigated the presence of urinary IL-6 in patients with BPS/IC to find a possible correlation with the symptoms before and after glycosaminoglycan substitution therapy. Urinary IL-6 levels of 25 BPS/IC patients were assessed semi-quantitavely (Milenia®Quickline) before and after intra-vesical glycosaminoglycan substitution therapy. Patients received therapy twice weekly with 300 mg pentosanpolysulphate for 5 weeks. Responders were treated for another 5 weeks, whilst non-responders received 40 mg hyaluronic acid weekly for another 10 weeks instead. Treatment response was assessed by the visual analogue scale (VAS) for quality of life and O’Leary–Saint Symptom and Problem Index (OSPI) before, during the 5th week of the treatment and 1 week after the treatment. Before treatment, measurable IL-6 was found in urine samples from 9 out of 25 patients. After treatment, urinary IL-6 was detected in two patients only. The average VAS and OSPI scores before the treatment were 7.9 (4–10) and 25.4 (12–37), respectively. After the treatment, the average VAS and OSPI scores dropped to 5.5 (0–10) and 14.7 (1–29), respectively. No statistically significant difference was found between patients with and without urinary IL-6 and the VAS and OSPI scores before and after the treatment. The urinary IL-6 level in BPS/IC patients is neither suited as a diagnostic marker nor as a predictor of responses to therapies. For the future, it would be important to clarify whether there are subsets of patients with diseases of different aetiologies.