Serum amyloid A is a better predictive biomarker of mucosal healing than C-reactive protein in ulcerative colitis in clinical remission

Abstract

Background: Many studies have revealed that mucosal healing improves the long-term prognosis of ulcerative colitis. Frequent colonoscopy is difficult because of its invasiveness and cost. Therefore, in diagnosing and treating ulcerative colitis, noninvasive, low-cost methods for predicting mucosal healing using useful biomarkers are required in the clinical setting. This study aimed to evaluate whether serum amyloid A is a better serum biomarker than C-reactive protein in predicting mucosal healing in ulcerative colitis patients in clinical remission.

Methods: Ulcerative colitis patients whose C-reactive protein and serum amyloid A were measured within 1 month before and after colonoscopy were included in this retrospective study, and the relationship between the C-reactive protein and serum amyloid A values and the mucosal condition was analyzed. Mucosal condition was assessed using the Mayo Endoscopic Score, with score 0 or 1 indicating mucosal healing.

Results: A total of 199 colonoscopic examinations were conducted in 108 ulcerative colitis patients who underwent C-reactive protein and serum amyloid A blood tests. In clinical remission patients, serum amyloid A showed a strong correlation with mucosal inflammation compared to C-reactive protein and had excellent sensitivity and specificity rates with significant statistical significance.

Conclusions: Serum amyloid A is a more useful marker compared to C-reactive protein in predicting mucosal inflammation in ulcerative colitis patients in clinical remission.

Keywords: C-reactive protein; Mucosal healing; Serum amyloid a; Ulcerative colitis.

Fig. 1

Correlation between CRP/SAA and endoscopic findings. Only a low correlation is found between CRP and MES (r = 0.352, p = 03.38 × 10^− 7, a). On the contrary, SAA has a high correlation with MES (r = 0.614, p = 5.44 × 10^− 22, b). Moreover, trends of MES and inspection values (SAA and CRP) were evaluated using the Cochran-Armitage trend test. At MES 0, the ratio at which CRP and SAA are normal is the highest, and with increasing MES, the ratio gradually decreases. The decreasing trend in relation to MES was statistically significant in SAA (p < 0.05), but not in CRP (a, b). CRP, C-reactive protein; MES, Mayo Endoscopic Score; SAA, serum amyloid A

Fig. 2

Comparison of ROC curves for mucosal inflammation (MES 2 or 3) of SAA and CRP. The ROC curves of SAA and CRP in patients in clinical remission. In the ROC analysis, the area under the ROC curve of the SAA was 0.807, indicating a higher predictive power, but that of CRP was 0.701. Comparison of ROC curves for mucosal inflammation (MES 2 or 3) of SAA and CRP showed that SAA was superior and indicated statistical significance (p < 0.01). AUC, area under the receiver’s operating characteristic curve, CI, confidence interval; CRP, C-reactive protein; MES, Mayo Endoscopic Score; SAA, serum amyloid A

Fig. 3

Comparison of ROC curves for mucosal inflammation (MES 1 or 2 or 3) of SAA and CRP. The ROC curves of SAA and CRP in patients in clinical remission. In the ROC analysis, the area under the ROC curve of the SAA was 0.749, indicating a higher predictive power, whereas that of the CRP was 0.646. Comparison of ROC curves for mucosal inflammation (MES 1 or 2 or 3) of SAA and CRP showed that SAA was superior and indicated statistical significance (p < 0.01). AUC, area under the receiver’s operating characteristic curve; CI, confidence interval; CRP, C-reactive protein; MES, Mayo Endoscopic Score; SAA, serum amyloid A

Fig. 4

Comparison of ROC curves of mucosal inflammation (MES 2 or 3) of SAA and CRP when divided by disease duration. The ROC curves of SAA and CRP in patients in clinical remission when divided by disease duration. Disease duration was divided into three groups: 0–5 years (N = 69), 6–15 years (N = 88), and more than 16 years (N = 42). When examined by disease duration, comparison of ROC curves for mucosal inflammation (MES 2 or 3) of SAA and CRP showed that SAA was superior and indicated statistical significance in groups with disease duration of 0–5 years and 6–15 years. On the other hand, no statistical significance was shown in the group with disease duration of 16 years or more. AUC, area under the receiver’s operating characteristic curve; CRP, C-reactive protein; MES, Mayo Endoscopic Score; SAA, serum amyloid A