For a neonate detected by newborn screening (NBS) with a potential diagnosis of very-long chain acyl-coA dehydrogenase deficiency (VLCAD), the most frequent evaluations for diagnostic confirmation include a combination of plasma acylcarnitine profile and molecular testing. Functional testing, including fibroblast acylcarnitine profiling and leukocyte or fibroblast enzyme assay, can be useful adjunct testing if uncharacterized variants are found and the diagnosis remains unclear.

Optimal VLCAD management requires ongoing assessment of clinical and nutritional status. Outcome measures from dietary history, anthropometrics, and clinical and laboratory assessment are used to determine appropriateness of treatment recommendations. Close monitoring of growth, development, and medical and nutrition parameters is needed for all individuals diagnosed with VLCAD. Evidence suggests that cardiac function should be monitored as part of routine care with more frequent evaluations in those with a severe form of VLCAD.

Consensus for routine monitoring of VLCAD is limited in both the formal and gray literature. However, after completing the Delphi survey and Nominal Group process, there was consensus (>80%) to routinely measure creatine kinase (CK) and plasma carnitine (total, ester, free) to assess severity and guide treatment recommendations, while comprehensive metabolic panel (liver enzymes and glucose), plasma acylcarnitine profile, essential fatty acid profile and cardiac monitoring would be used as conditional monitoring for patients.

Normal or near-normal concentrations of CK can be expected when individuals are asymptomatic. A CK concentration >1000 U/L can be used to define rhabdomyolysis and the extent of CK increase may be the best marker for severity of metabolic decompensation. Several sources suggest that monitoring plasma acylcarnitine profiles, specifically C14:1 and other long chain species with 14 to 18 carbons and the ratio of C14:1/C14, can be useful. Concentrations are expected to decrease with treatment and may be normal or near normal in those with a mild phenotype when asymptomatic. However, acylcarnitine concentrations can be influenced by length of fasting, dietary intake and carnitine supplementation and these factors need to be considered in interpretation of the results. Elevations in C8 and C10 acylcarnitines suggest MCT supplementation.

Monitoring of essential fatty acids (linoleic acid, α-linolenic acid), and their derivatives (arachidonic acid and docosahexaenoic acid) as well as fat-soluble vitamins is suggested to assess the need for dietary modification or supplementation for those treated with a fat-restricted diet.