BACKGROUND: Primary carnitine deficiency (PCD) is an autosomal recessive disorder of fatty acid oxidation and has been associated to episodes of sudden death in the Faroe Islands. Data are presented from the nationwide population based Faroese screening program to find people with low carnitine levels indicating PCD.

METHODS: Whole blood samples from dried blood spots were analysed by tandem mass spectrometry with and without butylation. Genetic analyses were performed in all people with non-butylated free carnitine (fC0) below 7 μmol/L.

RESULTS: 55 % (n = 26,462) of the entire population was screened and 89 PCD patients were identified, yielding an overall prevalence of 1:297 of PCD in the Faroe Islands. Carnitine levels were positively correlated to age in both males and females (p < 0.003) although levels decreased in females when reaching fertile age. The gender difference in mean carnitine levels was significant during female fertile age (4.71 μmol/L fC0 in the age group 25-30 years, p < 0.01). A lower cut-off of 5 μmol/L in fC0 identified all homozygous for the severe genotype c.95A > G (p.N32S) (n = 20).

CONCLUSION: Carnitine levels differ by gender and age. A lower cut-off of 5 μmol/L in fC0 was appropriate to identify c.95A > G homozygotes. The prevalence of PCD in the Faroe Islands is the highest reported in the world (1:297).