Reference Values of Serum MMP-7 and a Novel Measurement Approach Using Dried Blood Spot: A Diagnostic Test for Biliary Atresia

Background: Matrix metalloproteinase-7 (MMP-7) holds great promise as a diagnostic marker for biliary atresia (BA). This study aimed to establish reference values of serum MMP-7 and explore a novel measurement approach using dried blood spot (DBS). Methods: This was a single-center diagnostic test. Serum and DBS MMP-7 concentrations were measured using an ELISA kit. Intraoperative cholangiography and subsequent histological examinations were used to confirm BA diagnoses. Findings: 176 infants without hepatobiliary diseases were enrolled in the control group. The median serum MMP-7 concentration was 7.53 ng/mL (IQR: 5.58, 10.26) compared with 13.82 ng/mL (IQR: 8.10, 19.80) in the neonatal subgroup. 568 cholestatic infants were enrolled, including 318 patients in the retrospective cohort and 250 in the prospective cohort. Using a cutoff value of 18 ng/mL, the area under the ROC curve (AUC) for the retrospective cohort was 0.967 (95% confidence interval [CI]: 0.947–0.988), with a sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 93.0%, 93.8%, 94.7%, and 91.9%, respectively. The model was prospectively validated and achieved a diagnostic sensitivity of 94.8% (146/154; 95%CI: 89.7%–97.6%), specificity of 87.0% (80/92; 95%CI: 77.9%–92.8%), PPV of 92.4% (146/158; 95%CI: 86.8%–95.8%), and NPV of 90.9% (80/88; 95%CI: 82.3%–95.7%). 136 samples were tested via both DBS and serum. Linear regression showed that DBS MMP-7 levels correlated well with serum results (R = 0.942, P < 0.001). Interpretation: MMP-7 levels can precisely diagnose BA. A reference range and cutoff value were established, which were higher in neonates. DBS could be an alternative approach to measuring MMP-7. Clinical Trial Registration Details: Prospectively registered at http://www.chictr.org.cn/ (ChiCTR2000032983). Funding Information: This study received financial support from Clinical Research Plan of SHDC (no. SHDC2020CR2009A), Shanghai Municipal Key Clinical Specialty (no. shslczdzk05703), National Natural Science Foundation of China (no. 81770519, no. 81771633, no. 81873545 and no. 81974059), The Science Foundation of Shanghai (no. 18411969100 and no. 19ZR1406600), and Children's National Medical Center (no. EK1125180104, no. EKYY20180204, EK112520180211 and no. EK112520180310). Declaration of Interests: Jiale Deng, Dake Yang, Weiwei Xiang, Xianghui Zhang and Zhuo Fang work for WuXi Diagnostics. All authors declared no other conflicts of interest. Ethics Approval Statement: This study was reviewed and approved by the Ethics Committee of Children’s Hospital of Fudan University (No.: 2020-296). This work was performed in compliance with the Declaration of Helsinki and other relevant regulations. Informed consent was obtained from the guardian of each participant before enrollment.