Hepatic technetium-99m-mebrofenin iminodiacetate scans and serum gamma-glutamyl transpeptidase levels interpreted in series to differentiate between extrahepatic biliary atresia and neonatal hepatitis

Hepatic technetium-99m-mebrofenin iminodiacetate (Tc-99m-mebrofenin IDA) sc ans and serum gamma -glutamyl transpeptidase (GGTP) have high sensitivity f or extrahepatic biliary atresia (EHBA). This study was based on the hypothe sis that the interpretation of results of 99mTc-mebrofenin IDA scans and se rum GGTP levels in series would result in a reduction of the false positivi ty observed with these tests individually. The aetiology of neonatal choles tasis in 132 study patients was: 25% (33/132) EHBA, 45.5% (60/132) neonatal hepatitis (NH) with an identifiable cause and 19.7% (26/132) idiopathic NH . Of the various clinical, biochemical and imaging parameters that were sig nificantly different between patient groups, sensitivity for EHBA was: seru m GGTP greater than or equal to 150 IU l(-1) (100%), Tc-99m-mebrofenin IDA scans (100%), pale stools (82.8%) and total serum bilirubin greater than or equal to 12 mg dl(-1) (66%). However, specificity ranged from 48.5 to 79%. Of the 63 patients who had non-excreting IDA scans, operative cholangiogra ms could be avoided on the basis of a specific aetiological diagnosis of NH , made concurrently, in only 9 infants. The rest (54) underwent operative c holangiograms; 21 (39%) of these had patent biliary trees and therefore und erwent the procedure unnecessarily. If serum GGTP (< 150 IU l(-1)) had been used as a screen after IDA scanning in these 54 patients, operative cholan giograms could have been avoided in another 12 patients and thereafter only 9/42 (21%) of the operative cholangiograms would have been considered unne cessary. Conclusion: A diagnostic algorithm is proposed wherein serum GGTP level (at a cut-off level that maintains 100% sensitivity for EHBA) is used in serie s with non-excreting Tc-99m-mebrofenin IDA scans (for patients with no spec ific aetiological label). This strategy reduces the false positivity of ind ividual tests.