Calibration of a strip test for urinary urobilinogen using a mercuric chloride assay with crystalline reference standards.

A strip test based on Ehrlich's reaction has improved specificity for urobilinogen in urine. Strip reactions are calibrated in mg/dl using a recently developed reference assay which is based on a mercuric chloride reaction and includes a crystalline reference standard. Strip reactions correlate well with the mercuric assay when the urine sample contains only urobilinogen. If a urine contains urobilin in addition to urobilinogen, the strip test gives slightly lower values than the reference assay. The strip test reacts only with urobilinogen but the reference assay measures urobilin as well as urobilinogen. Comparative data with both tests are included for normal and pathological urines. Reaction colors with the strip test have been characterized in L* a b* values, an international basis for color designation.