Diagnostic accuracy of serum matrix metalloproteinase-7 as a biomarker of biliary atresia in a large North American cohort

Abstract

Background and aims: High levels of serum matrix metalloproteinase-7 (MMP-7) have been linked to biliary atresia (BA), with wide variation in concentration cutoffs. We investigated the accuracy of serum MMP-7 as a diagnostic biomarker in a large North American cohort.

Approach and results: MMP-7 was measured in serum samples of 399 infants with cholestasis in the Prospective Database of Infants with Cholestasis study of the Childhood Liver Disease Research Network, 201 infants with BA and 198 with non-BA cholestasis (age median: 64 and 59 days, p = 0.94). MMP-7 was assayed on antibody-bead fluorescence (single-plex) and time resolved fluorescence energy transfer assays. The discriminative performance of MMP-7 was compared with other clinical markers. On the single-plex assay, MMP-7 generated an AUROC of 0.90 (CI: 0.87-0.94). At cutoff 52.8 ng/mL, it produced sensitivity = 94.03%, specificity = 77.78%, positive predictive value = 64.46%, and negative predictive value = 96.82% for BA. AUROC for gamma-glutamyl transferase = 0.81 (CI: 0.77-0.86), stool color = 0.68 (CI: 0.63-0.73), and pathology = 0.84 (CI: 0.76-0.91). Logistic regression models of MMP-7 with other clinical variables individually or combined showed an increase for MMP-7+gamma-glutamyl transferase AUROC to 0.91 (CI: 0.88-0.95). Serum concentrations produced by time resolved fluorescence energy transfer differed from single-plex, with an optimal cutoff of 18.2 ng/mL. Results were consistent within each assay technology and generated similar AUROCs.

Conclusions: Serum MMP-7 has high discriminative properties to differentiate BA from other forms of neonatal cholestasis. MMP-7 cutoff values vary according to assay technology. Using MMP-7 in the evaluation of infants with cholestasis may simplify diagnostic algorithms and shorten the time to hepatoportoenterostomy.

Graphical abstract

FIGURE 1

Patient distribution and etiological diagnoses of patients without BA. Flowchart of subject enrollment. A total of 399 infants were enrolled in this study, among whom 201 infants had BA and 198 had other cholestatic diseases (non-BA). The most common diagnoses seen in the non-BA group are outlined. Abbreviations: A1AT, alpha-1-antitrypsin; BA, biliary atresia; INH, idiopathic neonatal hepatitis; PFIC, progressive familial intrahepatic cholestasis.

FIGURE 2

(A) Shows the AUROC of MMP-7 in the North American cohort. (B) Diagnostic performance of MMP-7 at a cutoff of 52.8 ng/mL and its comparison to a Yang et al study in the Chinese population. (C–F) Correlation of MMP-7 with age in healthy infants and in the entire cohort (BA and non-BA cohorts), BA cohort alone, and BA cohort of infants younger than 60 days of age. (G) Pie charts show the percentage of patients above the cutoff of 52.8 ng/mL for patients with BA (left) and the percentage of patients below the cutoff of 52.8 ng/mL for patients without BA (right). The distribution of diagnoses of patients without BA with MMP-7 levels above 52.8 ng/mL is displayed in the far right. Abbreviations: A1AT, alpha-1-antitrypsin; BA, biliary atresia; MMP-7, matrix metalloproteinase-7.

FIGURE 3

Comparison of MMP-7 performance with other clinical variables. (A) AUROCS for serum MMP-7, GGT, stool color, and pathology in differentiating BA from non-BA cholestasis in logistic regression analysis. The AUROC value is shown with a 95% CI. (B) Overall AUC values for each variable, along with sensitivity, specificity, NPV, and PPV calculated at each respective optimal cutoff point. Abbreviations: GGT, gamma-glutamyl transferase; MMP-7, matrix metalloproteinase-7.

FIGURE 4

ROC curves for TR-FRET and Luminex assays. (A) Superimposed ROC curves for the Luminex assay (black line) and TR-FRET assay (red line). (B) The table on the right displays the AUROCs of Luminex and TR-FRET assays, along with sensitivity, specificity, NPV, and PPV calculated at each respective cutoff point. (C) Scatter plots show simple logistic regression analysis of MMP-7 concentration and postnatal age in days in healthy controls using the TR-FRET assay. (D) Graphs display the median and IQR of MMP-7 concentrations in healthy controls, non-BA cholestasis, and BA using TR-FRET assays. Abbreviations: BA, biliary atresia; FRET, fluorescence energy transfer; MMP-7, matrix metalloproteinase-7.

FIGURE 5

Diagram depicting the cutoffs for serum MMP-7 that increase sensitivity and specificity to 95%, while maintaining high NPV for the TR-FRET (upper panel) and bead-based Luminex assays (lower panel). Abbreviations: BA, biliary atresia; FRET, fluorescence energy transfer.