Clinical significance of fecal calprotectin for the early diagnosis of abdominal type of Henoch–Schonlein purpura in children

The objective of this study is to explore the value of fecal calprotectin (FC) for early screening of the abdominal type of Henoch–Schonlein purpura (AHSP) in children. The study cohort included 40 children with AHSP treated at Shengjing Hospital of China Medical University from November 2014 to November 2015, and 40 children hospitalized in the Division of Pediatric Orthopedics in the corresponding period were selected as a control group. Fresh fecal samples were collected in the acute phase of the first visit (FC1), 3 days after treatment (FC2), and 7 days after treatment (FC3) from the AHSP group and the control group. Calprotectin levels in the fecal samples were measured using an enzyme-linked immunosorbent assay. At the same time, gastrointestinal performance and the laboratory examination indicators white blood cell (WBC) count and C-reactive protein (CRP) level were recorded. The median levels of FC1 (3053 μg/g) and FC2 (2778.3 μg/g) were higher than in the control group (102.5 μg/g), with significant differences among the three groups (p < 0.001). FC levels gradually decreased in remission, and the level of FC3 on day 7 was close to that of the control samples (p > 0.05). When the optimal cut-off was 264.5 μg/g, the area under the receiver operating characteristic (ROC) curve of FC for diagnosis of AHSP was 0.961 with a corresponding sensitivity and specificity of 93.1 and 87.5%, respectively. The levels of FC in children with AHSP were positively correlated with WBC count (r _s = 0.688) and CRP value (r _s = 0.513). The area under the ROC curve of WBC count for screening AHSP was 0.785 when the optimal cut-off value was 11.1 × 10⁹/L with a corresponding sensitivity and specificity of 81.5 and 62.5%, respectively. The area under the ROC curve of CRP was 0.963 when the optimal cut-off value was 5.72 mg/dL with a corresponding sensitivity and specificity of 88.9 and 100%, respectively. Comparisons of FC, WBC count, and CRP level as diagnostic indicators of AHSP showed that the sensitivity of FC was higher than that of the WBC count and CRP level, and its diagnostic value was better than that of the WBC count. The levels of FC began to increase in the early stages of AHSP, showing a decreasing tendency in remission and tending to be within a normal range after a week or so. For the early diagnosis of AHSP, FC with a cut-off level of 264.5 μg/g has good sensitivity and specificity. The sensitivity of FC is better than that of the traditional inflammation indicators CRP and WBC count, and its diagnostic performance is better than WBC count; FC can be suitable as a new marker for the early diagnosis of AHSP.