Transferrin isoelectric focusing for the investigation of congenital disorders of glycosylation: analysis of a ten‐year experience in a Brazilian center

To characterize cases of suspected congenital disorders of glycosylation (CDG) investigated in a laboratory in southern Brazil using the transferrin isoelectric focusing TfIEF test from 2008 to 2017. Observational, cross‐sectional, retrospective study. The laboratory records of 1,546 individuals (median age = 36 months, 25‐75 IQR = 10‐108; males = 810) submitted to the TfIEF test during the period were reviewed. Fifty‐one individuals (3%) had an altered TfIEF pattern (5 ± 2.8 cases/year; median age = 24 months, 25‐75 IQR = 11‐57 months; males = 27, 53%). For 14 of them, data on diagnosis conclusion were available (classic galactosemia = 4; hereditary fructose intolerance = 4; peroxisomal diseases = 2; PMM2‐CDG = 2; MPDU1‐CDG = 1; SLC35A2‐CDG = 1).Comparing the cases with the normal and altered TfIEF patterns, there was a higher prevalence of altered cases in the age group from 11 months to 3 years. There was an increase in the likelihood of change in TfIEF, especially in the presence of inverted nipples or liver disease. The data suggest that the investigation of a case with suspected CDG is a complex problem, being aggravated by the existence of other IEMs (inborn errors of metabolism) associated with altered TfIEF pattern and lack of access to confirmatory tests. The presence of inverted nipples and liver disease, especially in individuals aged 11 months to 3 years, should suggest the need for TfIEF investigation. Caracterizar os casos com suspeita de CDG investigados em laboratório do sul do Brasil pelo exame de IEFTF de 2008 a 2017. Estudo observacional, transversal, retrospectivo. Foram revisadas as fichas laboratoriais de 1.546 indivíduos (mediana de idade = 36 meses, IQ 25‐75 = 10‐108; sexo masculino = 810) que fizeram o exame de IEFTF no período. Cinquenta e um indivíduos (3%) apresentaram padrão alterado na IEFTF (5 ± 2,8 casos/ano; mediana de idade = 24 meses, IQ 25‐75 = 11‐57 meses; sexo masculino = 27, 53%). Para 14 deles, estavam disponíveis dados sobre a conclusão do diagnóstico (galactosemia clássica = 4; intolerância hereditária à frutose = 4; doenças peroxissomais = 2; PMM2‐CDG = 2; MPDU1‐CDG = 1; SLC35A2‐CDG = 1). Comparando os casos com padrão normal e alterado na IEFTF, houve maior prevalência de casos alterados na faixa etária de 11 meses a 3 anos. Verificou‐se um aumento na probabilidade de alteração na IEFTF principalmente na presença de mamilos invertidos ou de hepatopatia. Os nossos dados sugerem que a investigação de um caso com s