2.3 Case-control study
To determine the potential biomarker of arsenic-related pruritus, we
recruited 77 cases with severe itch, 95 cases with mild itch, and 57
controls with no itch from the participants in Shimen, and tested their
serum levels of known biomarkers for itch, including β-endorphin,
substance P, nerve growth factor, histamine, interleukin-31, IgE,
endothelin-1, and 5-hydroxytryptamine. Participants of the three groups
were roughly matched by age and sex. Participants with eczema, psoriasis
or other conditions that may cause itch were excluded.