Inflammation and Symptom Change in Interstitial Cystitis or Bladder Pain Syndrome: A Multidisciplinary Approach to the Study of Chronic Pelvic Pain Research Network Study.

Objective: To explore inflammatory factors that influence symptom changes in interstitial cystitis or bladder pain syndrome (IC or BPS). This longitudinal, prospective study examined the association of inflammation elicited by Toll-like receptor (TLR) stimulation in peripheral blood mononuclear cells (PBMCs) and diurnal cortisol rhythms with changes in painful and urinary symptoms of IC or BPS and symptom flares over a 48-week period.

Methods: Participants were 24 women meeting criteria for IC or BPS who supplied blood for isolation of PBMCs and 3 days of salivary cortisol samples prior to a baseline visit. Participants completed the Genitourinary Pain Index (pain and urinary subscales) and reported symptom flares every 2 weeks for 48 weeks. Mixed effects longitudinal and regression models were used to determine if inflammatory variables were associated with the changes in IC or BPS symptoms (time × variable interactions), and the probability of a symptom flare.

Results: Elevated TLR-4 inflammation (P = .031) and elevated TLR-2 inflammation (P = .045) from PBMCs, and flattened diurnal cortisol slope (P = .012) were each associated with less improvement in genitourinary pain over time. Additionally, elevated TLR-4 inflammation was associated with less improvement in urinary symptoms (P = .018), whereas TLR-2 inflammation and cortisol slopes were not (both P > .16). In contrast, no inflammatory measure was associated with an increased likelihood of reporting a symptom flare (all P > .25).

Conclusions: TLR-mediated inflammation and diurnal cortisol slope may be useful as markers of symptom changes in IC or BPS.