Gross findings from cystoscopy and pathohistological findings from bladder biopsy are important in interstitial cystitis (IC) diagnosis. Differential diagnosis between non-Hunner (N type) and Hunner-type (H type) lesions is known to greatly influence disease prognosis and patient quality of life. If the H type, which is thought to be a more severe IC, is treated appropriately with electrical ablation, the treatment outcome with bladder hydrodistension alone would be insufficient. However, limitations of the invasive gross diagnosis using cystoscopy and bladder biopsy are self-evident. Furthermore, no consistent standard has yet been established for pathohistological diagnosis using biopsy. Therefore, discovering a convenient and useful biomarker for differential diagnosis of the two disease types is necessary.
Recently, there have been a few reports on correlation between blood inflammatory markers and disease prognosis in chronic inflammation and malignant tumors. Therefore, we assessed usefulness of presurgical serum C-reactive protein (CRP) level as a biomarker for Hunner lesions in IC prior to performing bladder hydrodistension.

This study included the participants who were diagnosed with or without IC at our hospital between April 2007 and September 2017.
Patients suspected of having IC were enrolled and divided into non-IC hypersensitive bladder (S), N type (N), and H type (H) groups according to cystoscopy findings during surgery. A normal group (control [C]), consisting of patients free of urinary disorders, was also included. Serum CRP levels among the 4 groups were compared and correlations of preoperative CRP levels with the IC Symptom Index (ICSI)/IC Problem Index (ICPI) and the presence of Hunner lesions were evaluated. Patients with acute phase infections such as urinary tract infections and chronic inflammatory systemic diseases such as rheumatoid arthritis and collagen disease were excluded from this study. This study was approved by the ethics committee of our institution.

Of the 162 subjects analyzed, 54 were male (mean age, 65.4 ± 12.7 years). Table shows that the participants’ characteristics and preoperative serum CRP levels. There was no statistically significant difference in the ratio of men to women in the participants among four groups. Serum CRP levels were as follows: C group (n = 57), 0.04 ± 0.03 mg/dL; S group (n = 54), 0.06 ± 0.05 mg/dL; N group (n = 18), 0.05 ± 0.04 mg/dL; and H group (n = 33), 0.13 ± 0.12 mg/dL. The H group had significantly higher serum CRP levels than the other 3 groups (P < 0.001). Both total ICSI (H group, 13.4 ± 3.8; N group, 8.2 ± 3.3; P < 0.001) and total ICPI scores (H group, 11.5 ± 3.6; N group, 6.9 ± 3.0; P < 0.001) were significantly higher in the H group than in the N Group. Moreover, both the total ICSI and total ICPI scores were positively correlated with CRP level (ICSI: r = 0.486, P < 0.001; ICPI: r = 0.527, P < 0.001). The sensitivity and specificity of CRP levels were 72.7% and 77.8%, respectively, with an area under the curve of 0.777 in ROC analysis for presence of Hunner lesion; CRP level cutoff value was 0.07 mg/dL.

Unfortunately, from the results of this study, we could not differentiate between interstitial cystitis and non-IC hypersensitive bladder or normal bladder with CRP values.
Although serum CRP levels alone were insufficient for differential diagnosis between N-type IC and hypersensitive bladder, preoperative CRP levels were high in H-type IC patients. The results suggest the potential usefulness of CRP levels as a presurgical marker in the differential diagnosis of Hunner lesions. Additionally, CRP levels correlated with the severity of IC symptoms.

Serum CRP levels might be a marker for the presence of Hunner lesion in patients with interstitial cystitis.