Long-term monitoring of fatty acid oxidation defects: results from a MetabERN survey

Background Implementation of long-chain fatty acid oxidation defects (LCFAOD) in newborn screening (NBS) programs allows for pre-symptomatic diagnosis and treatment. The long-term natural history of NBS LCFAOD patients is largely unknown and may differ from clinically diagnosed pre-NBS patients. This complicates long-term monitoring of LCFAOD and may cause high monitoring variability. To gain insight in current clinical practice, we performed a web-based questionnaire among all metabolic members of the European Reference Network for Hereditary Metabolic Disorders (MetabERN). Results Thirty-seven colleagues representing at least 35 European metabolic centres shared their experience and results were discussed at the European Metabolic Group (EMG) meeting 2022. The centres concurred in many aspects of long-term monitoring of LCFAOD including the frequency of clinical visits, determination of laboratory parameters, cardiac monitoring and retinopathy screening. Main discrepancies comprised hepatic imaging, glucose monitoring and electrophysiological investigations. Conclusions Discrepancies may reflect differences in local availability of monitoring tools, the inclusion of LCFAOD in NBS programs as well as differences in local genotypes and phenotypes. Because monitoring strategies are largely based on the natural disease course of clinically identified patients, there might be over-monitoring of some NBS patients. Nevertheless, we advocate long-term monitoring because resulting information is essential to further characterize the natural disease course, develop evidence-based guidelines and provide a basis for evaluation of future therapies.