Screening tests in acute porphyria.

Two recognized screening procedures for rapid evaluation of urinary porphobilinogen (PBG) concentrations are compared with quantitative PBG determinations (expressed as mg/24 hours and as a concentration in urine, mg/liter). One hundred ninety-one 24-hour urine specimens from 74 patients with suspected or documented acute type porphyria are included in this investigation. The two screening tests are compared with regard to sensitivity and method of performance. In this study, the Watson-Schwartz and Hoesch tests are positive at PBG concentrations in urine greater than 9 mg/liter. Both methods produced the characteristic pink color only once at a concentration below 3 mg/liter. Both methods are useful in detecting the abnormal concentration of urinary PBG observed during an acute porphyric attack. The Hoesch procedure provides a simple and rapid evaluation of urinary PBG. Positive results from either screening test demand quantitative urinary PBG determinations to confirm the suspected abnormality.