nal analyses.
For 81% of the sample, phlebotomy occurred within
2 days of the sleep study; the maximum lag was 28 days
(mean time: 3.9 6.8 days). Table shows the average serum
ferritin and sleep parameter measurements for each diagnostic
group. The mean serum ferritin level did not differ
significantly among groups. Participants were classified as
having low iron stores using World Health Organization
guidelines, such that values of less than 12 mg/L for children
younger than 5 years and 15 mg/L for children 5 years and
older were considered low. These cutoffs described similar
proportions in each of the diagnostic groups (autism:
n ¼ 11, 16%, typically developing: n ¼ 3, 17%, developmental
delay: n ¼ 3, 19%; c2 ¼ 0.06, P ¼ 0.97). Of note, only six
patients (6%) in this study had ferritin levels above the
commonly used clinical threshold for intervention of 50 mg/
L. The serum ferritin results in this subgroup of 102 participants
with a sleep study did not differ from those found
in the larger study’s full sample of 188 patients (data
available upon request)