A simplified fecal leukocyte esterase strip test results as a low cost, widely available, alternative bowel inflammation biomarker.

ABSTRACT

BACKGROUND/PURPOSE: Leukocyte esterase strips have been widely used to detect the presence of leukocyte in human body fluids. We investigated the correlation between fecal leukocyte esterase (FLE) and fecal calprotectin (FC) levels and compared manual with machine automated interpretation of FLE level. METHODS: This prospective study enrolled inflammatory bowel disease and colitis patients in National Taiwan University Hospital from Dec 2021 to Feb 2022. FLE and FC measured using the same sample were compared with various FC cutoff values. The correlation between values indicated by the two tests was analyzed. Sensitivity, specificity, positive and negative predictive values, and area under the receiver operating characteristic curve (AUROC) were calculated using SAS. RESULTS: A total of 103 samples were analyzed. The correlation between FLE and FC level was moderate and positive (r = 0.3505, P = 0.0003). With an FLE reading more than 1+ indicating mucosa inflammation, when the FC cutoff was 50, 250, and 500 mg/kg, the sensitivities of FLE readings were 60.3 %, 74.3 %, and 84.6 %, respectively, and the specificities were 62.9 %, 58.8 %, and 58.4 %, respectively. With an FLE reading greater than 1+ indicating mucosa inflammation, FLE reflected FC with AUROC values at the optimal cutoff (500 mg/kg) of 0.72. No difference was noted between manual and machine readings for FLE. CONCLUSION: Positive FLE can predict FC levels of more than 500 mg/kg. The test is widely available, produces results on the same day, and is low cost; therefore, FLE should be further investigated for use in bowel inflammation monitoring.