Carnitine levels in 26,462 individuals from the nationwide screening program for primary carnitine deficiency in the Faroe Islands

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).