Papers

Screening of newborn infants for cholestatic hepatobiliary disease with tandem mass spectrometry

Imran Mushtaq, research fellow, ^a Stuart Logan, senior lecturer in epidemiology, ^b Michael Morris, chemist (mass spectrometry applications), ^c Andrew W Johnson, senior lecturer in biochemistry, ^a Angie M Wade, lecturer in medical statistics, ^b Deirdre Kelly, consultant paediatric hepatologist, ^d Peter T Clayton, professor of paediatric metabolic disease and hepatology. ^a

^a Biochemistry Unit, Institute of Child Health, University College London, London WC1N 1EH, ^b Epidemiology and Biostatistics Unit, Institute of Child Health, ^c Micromass UK Limited, Wythenshawe, Manchester M23 9LZ, ^d Liver Unit, Birmingham Children's Hospital, Ladywood Middleway, Ladywood, Birmingham B16 8ET

Correspondence to: P T Clayton P.Clayton{at}ich.ucl.ac.uk

Objective: To assess the feasibility of screening for cholestatic hepatobiliary disease and extrahepatic biliary atresia by using tandem mass spectrometry to measure conjugated bile acids in dried blood spots obtained from newborn infants at 7-10 days of age for the Guthrie test.
Setting: Three tertiary referral clinics and regional neonatal screening laboratories.
Design: Unused blood spots from the Guthrie test were retrieved for infants presenting with cholestatic hepatobiliary disease and from the two cards stored on either side of each card from an index child. Concentrations of conjugated bile acids measured by tandem mass spectrometry in the two groups were compared.
Main outcome measures: Concentrations of glycodihydroxycholanoates, glycotrihydroxycholanoates, taurodihydroxycholanoates, and taurotrihydroxycholanoates. Receiver operator curves were plotted to determine which parameter (or combination of parameters) would best predict the cases of cholestatic hepatobiliary disease and extrahepatic biliary atresia. The sensitivity and specificity at a selection of cut off values for each bile acid species and for total bile acid concentrations for the detection of the two conditions were calculated.
Results: 218 children with cholestatic hepatobiliary disease were eligible for inclusion in the study. Two children without a final diagnosis and five who presented at <14 days of age were excluded. Usable blood spots were obtained from 177 index children and 708 comparison children. Mean concentrations of all four bile acid species were significantly raised in children with cholestatic hepatobiliary disease and extrahepatic biliary atresia compared with the unaffected children (P<0.0001). Of 177 children with cholestatic hepatobiliary disease, 104 (59%) had a total bile acid concentration >33 µmol/l (97.5th centile value for comparison group). Of the 61 with extrahepatic biliary atresia, 47 (77%) had total bile acid concentrations >33 µmol/l. Taurotrihydroxycholanoate and total bile acid concentrations were the best predictors of both conditions. For all cholestatic hepatobiliary disease, a cut off level of total bile acid concentration of 30 µmol/l gave a sensitivity of 62% and a specificity of 96%, while the corresponding values for extrahepatic biliary atresia were 79% and 96%.
Conclusion: Most children who present with extrahepatic biliary atresia and other forms of cholestatic hepatobiliary disease have significantly raised concentrations of conjugated bile acids as measured by tandem mass spectrometry at the time when samples are taken for the Guthrie test. Unfortunately the separation between the concentrations in these infants and those in the general population is not sufficient to make mass screening for cholestatic hepatobiliary disease a feasible option with this method alone.