Background Iron and vitamin D have been implicated to play an important role in cognition and neurodevelopment respectively. Existing evidence suggests that correcting deficiencies in both these nutrients can improve Autism Spectrum Disorder (ASD) symptoms. Children with ASD are also at greater risk for these deficiencies due to behavioural difficulties and food selectivity. Extant literature shows highly variable rates of these deficiencies and variable practices in routine screening among different populations.
Objectives The objectives of this study were to 1. Determine occurrence of iron and vitamin D deficiency in the sample population, 2. Identify predictors of the presence of these deficiencies if any and 3. Elucidate factors influencing screening for these deficiencies in children with ASD.
Methods This was a retrospective cross-sectional review of case records of all patients with ASD who were seen at a tertiary developmental paediatric centre in Singapore from January 2018 to June 2018. Inclusion criteria was 1. Child age 0 to 7 years and 2. Diagnosis of ASD following clinical evaluation by a developmental paediatrician or formal psychological evaluation with the Autism Diagnostic Observation Schedule. Exclusion criteria was 1. Chronic medical conditions and 2. Genetic syndromes. Information on demographic variables, ASD-related variables and other medical conditions was abstracted using a structured data collection form. Presence of iron deficiency (serum ferritin < 12µg/L or transferrin saturations < 10%), vitamin D deficiency (25-hydroxyvitamin D [25(OH)D] < 10 µg/L) and vitamin D insufficiency (25(OH)D between 10.1–29.9 µg/L) was determined from review of laboratory investigations. Descriptive statistics were used to assess for prevalence of iron and vitamin D deficiencies. Logistic regression was used to identify predictors of iron and vitamin D deficiencies and chi square tests were used to compare children who were and were not offered screening for these deficiencies.
Results The sample consisted of 480 children (81% males, 19% females) with a mean age of 4.5 years (SD 1.3). Of this, only 20.2% (N=97) of children were screened for iron deficiency and 18.3% (N=88) were screened for vitamin D deficiency using blood tests. The prevalence of iron deficiency was 19% (N=18). Younger children were more likely to have iron deficiency (B=1.06, p=0.02). The prevalence of vitamin D insufficiency was 38% (N=33) and that of vitamin D deficiency was 1.1% (N=1). Older children were more likely to have vitamin D deficiency or insufficiency (B=1.07, p=0.01). Only 20.8% (N=100) of children from the entire sample were offered screening blood tests; children with greater severity of disease (χ2= 9.80, p=0.002) and those with a history of selective feeding (χ2= 8.27, p=0.004) were more likely to be offered screening tests.
Conclusions The prevalence of both iron deficiency and vitamin D deficiency/insufficiency was high in this sample compared to the general population. Of note, only a small proportion of children were offered screening and eventually screened for these deficiencies. Apart from child age, there were no significant child or disease characteristics that predicted these deficiencies. Routine screening of all children with ASD for iron and vitamin D deficiency is recommended.
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