Evaluation of Serum Calprotectin as an Alternative Diagnostic Marker for Intrahepatic Cholestasis of Pregnancy

<b>Background/Objectives</b>: Intrahepatic cholestasis of pregnancy (ICP) is characterised by unexplained intense pruritus during pregnancy. While serum bile acid (BA) is the standard diagnostic marker for ICP, we explored the potential of serum calprotectin as an alternative diagnostic marker for ICP. <b>Methods</b>: Leftover serum specimens with known serum BA levels, collected from non-pregnant women and pregnant women with an ICP, were used to measure serum calprotectin levels using the Human calprotectin L1/S100-A8/A9 ELISA kit. <b>Results</b>: Serum calprotectin levels were measured in 79 pregnant women with ICP (median [interquartile range] 28 year; serum BA 20 [13.7-35.7] μMol/L; calprotectin159 pg/mL [122.2-212.3]); 43 pregnant women without ICP (age 28 years; serum BA 3.6 [2.1-5.8] μMol/L; calprotectin 146.5 pg/mL [75.8-194.8]), and 59 non-pregnant women (age 28 years; serum BA 3.5 [1.6-5.1 μMol/L; calprotectin 82.4 pg/mL [48.8-137.2]). Compared to non-pregnant women, calprotectin levels were significantly elevated among pregnant women with (<i>p</i> < 0.001) or without ICP (<i>p</i> = 0.01). Calprotectin levels were comparable between pregnant women with and without ICP (<i>p</i> = 0.15). The areas under the ROC curve, to differentiate the presence and absence of ICP, were 0.940 (0.903-0.977; <i>p</i> < 0.001) and 0.681 (0.604-0.759; <i>p</i> < 0.001) for BA and calprotectin, respectively. <b>Conclusions</b>: Serum calprotectin is raised in pregnant women regardless of the presence or absence of ICP and had an inferior diagnostic performance for ICP compared to BA. This information is crucial for understanding the challenges in ICP diagnosis and the limitations of serum calprotectin as an alternative marker.