A High Urinary Urobilinogen / Serum Total Bilirubin Ratio Reported in Abdominal Pain Patients Can Indicate Acute Hepatic Porphyria

Abstract

Background: Due to its variable symptoms and nonspecific laboratory test results during routine examinations, acute hepatic porphyria (AHP) has always been a diagnostic dilemma for physicians. Correct diagnosis mainly depends on the elevated urinary porphobilinogen (PBG) level, which is not a routine test performed in the emergency department. Therefore, identifying a more convenient indicator during routine examinations is important to improve the diagnosis of AHP.Methods: In this retrospective study, we enrolled 12 AHP patients and 100 patients with abdominal pain of other causes as the control groups in Qilu hospital of Shandong University between 2015 and 2021. The clinical manifestations and laboratory result data including urinary urobilinogen/serum total bilirubin ratio were compared between these two groups. The diagnostic performance of urinary urobilinogen/serum total bilirubin ratio was measured as sensitivity, specificity, and accuracy. The cut-off for optimal clinical performance was determined by the receiver operator characteristic (ROC) curve. Results were considered significant at a P < 0.05.Results: Compared with the control groups, AHP patients showed a significantly higher urinary urobilinogen level (P < 0.05). However, we showed that the higher urobilinogen level was caused by a false-positive result due to elevated urine PBG. Hence, we used serum total bilirubin, an upstream substance of urinary urobilinogen synthesis, for calibration. A remarkable increase in the urinary urobilinogen/serum total bilirubin ratio was observed in AHP patients. The area under the ROC curve of this ratio for AHP was 1.000 (95% confidence interval, 1.000–1.000, P < 0.01). A cutoff value of 3.22 for the urinary urobilinogen/serum total bilirubin ratio yielded a sensitivity of 100% and a specificity of 100% to distinguish AHP patients from the controls.Conclusion: A reported high urinary urobilinogen level that was adjusted by the serum total bilirubin level (urinary urobilinogen/serum total bilirubin ratio) could be used as a sensitive and specific indicator for AHP in patients with abdominal pain.