DETECTION OF LATENT VARIEGATE PORPHYRIA BY FLUORESCENCE EMISSION-SPECTROSCOPY OF PLASMA

The plasma of patients with overt variegate porphyria contains porphyr in with a fluorescence emission maximum at about 626 nm, which is diag nostic for the condition. We have evaluated qualitative fluorescence e mission scanning of saline-diluted plasma as a method for the identifi cation of asymptomatic carriers of the gene for variegate porphyria. P lasma from 3 6 unrelated patients with variegate porphyria, 136 of the ir asymptomatic first- and second-degree relatives aged 15 years or ov er, and 322 normal subjects was scanned. An emission maximum between 6 21 and 627 nm was observed in the 36 patients with variegate porphyria and 54 of their relatives, but not in any normal subject, nor in 56 p atients with other types of porphyria. For the detection of asymptomat ic adult carriers of the gene for variegate porphyria, fluorescence em ission scanning of plasma appears to be 100% specific, with a sensitiv ity of 86% (95% confidence interval 71-98%). In contrast, the sensitiv ity of faecal porphyrin analysis as a test for adult gene carriers was 36%. These results suggest that fluorescence emission scanning of pla sma should replace faecal porphyrin analysis as the test of first choi ce for this purpose.