THE INCIDENCE OF ELEVATIONS IN URINE 5-HYDROXYINDOLEACETIC ACID

A 24-hour urine collection for 5-hydroxyindoleacetic acid (HIAA) is co mmonly performed to evaluate patients with suspected carcinoid syndrom e. However, car cinoids are rare, and elevated results are common even when using an analytically specific method. To characterize this prob lem, the incidence of elevated results was examined in a population of 947 patient specimens received in a clinical reference laboratory set ting. Using a reference limit of 15 mg/d identified 7.9 percent of the results as elevated, with 3 percent >100 mg/d, and about 1 percent >3 50 mg/d. Males showed 14 percent >15 mg/d compared to 5.2 percent for females. Characterization of incomplete and excess 24-hr urine collect ions is facilitated by use of a creatinine ratio, with a reference lim it of 14 mg/g creatinine equivalent to 15 mg/d. Given the frequency of elevated results, HIAA should be used to support the diagnoses of car cinoid only when consistent with other objective findings.