Which laboratory test should be ordered for a 16‑year‑old male with autism who is taking vitamin C, vitamin D, and fluticasone nasal spray during his annual physical?

Laboratory Testing for a 16-Year-Old Male with Autism During Annual Physical

For a 16-year-old male with autism on vitamin C, vitamin D, and Flonase during his annual physical, order serum 25-hydroxyvitamin D levels to confirm adequate supplementation and consider folate receptor autoantibodies (FRAA) testing if there are any signs of developmental regression or metabolic concerns.

Standard Screening for Adolescents with Autism

Vitamin D Monitoring

• Measure serum 25-hydroxyvitamin D (25(OH)D) levels to ensure the current supplementation is achieving adequate levels, as vitamin D deficiency is common in children with autism and correlates with autism severity 1, 2, 3.
• Target serum levels should be at least 40-50 nmol/L (16-20 ng/ml) for bone health, though higher levels may benefit autism symptoms 4, 5.
• Children with autism have been shown to have significantly lower vitamin D levels than neurotypical controls (38 ng/ml vs. 56 ng/ml) 2.

Autism-Specific Biomarker Testing

• Consider folate receptor autoantibodies (FRAA) as the primary biomarker recommended by the American Academy of Pediatrics to identify patients who may benefit from leucovorin therapy, particularly if there are any signs of developmental regression or metabolic concerns 6, 7.
• This test is especially important if the patient has shown any atypical developmental regression, seizures, hypotonia, dystonia, or movement disorders 7.

Conditional Testing Based on Clinical Presentation

Metabolic Screening (Only if Clinical Indicators Present)

The American College of Medical Genetics does not recommend routine metabolic testing in all autism cases without specific clinical indicators 8. However, pursue metabolic evaluation if any of the following are present:

• True developmental regression (neurodegeneration occurring outside the typical 18-24 month speech-loss window) 8, 7
• Worsening neurological symptoms, lethargy, or poor physical endurance 8
• Seizures (especially refractory or myoclonic-atonic types) 8, 7
• Hypotonia, dystonia, or movement disorders 7
• Physiologic abnormalities such as acidosis 8

If these indicators are present, obtain:

• Complete blood count 8
• Serum metabolic profile 8
• Serum amino acids 8
• Homocysteine and methylmalonic acid (more sensitive than serum B12 alone for assessing functional B12 status and folate metabolism) 6, 7
• Ferritin and total iron binding capacity 6, 7

Additional Folate Pathway Assessment

If cerebral folate deficiency is suspected based on regression, seizures, or movement disorders, consider:

• Genetic testing for MTHFR and other folate metabolism pathway variants 6, 7
• Serum B12 levels (noting if elevated, which may indicate underlying metabolic issues) 7

Mitochondrial Testing

If mitochondrial dysfunction is suspected (constitutional symptoms, repeated regressions after age 3, multiple organ dysfunctions):

• Lactate and pyruvate as key indicators 6

Adolescent-Specific Considerations

Obesity and Metabolic Screening

• Assess for obesity during physical examination, as children with autism have increased odds of obesity and significantly increased risk of obesity-related metabolic complications 6.
• If obese, check for acanthosis nigricans on physical exam as an indicator of insulin resistance 6.
• Consider screening for vitamin D deficiency even more aggressively if obese, as patients with obesity frequently have micronutrient deficiencies despite consuming calorically dense foods 6.

PCOS Screening (If Female)

• Not applicable to this male patient, but worth noting that obesity in adolescent females with autism increases PCOS risk, requiring DHEA-S and LH/FSH ratio testing 6.

Common Pitfalls to Avoid

• Don't assume vitamin D supplementation is adequate without checking levels – verify that current supplementation achieves therapeutic serum concentrations, as inadequate levels play a role in autism severity 1, 5, 2, 3.
• Don't overlook signs of regression – any developmental regression outside the typical 18-24 month window or involving motor skills (not solely speech) should trigger expanded metabolic evaluation 7, 9.
• Don't perform routine metabolic screening without clinical indicators – the American College of Medical Genetics emphasizes that metabolic disorders in autism are "low incidence yet high impact," and routine screening is not recommended without specific red flags 8.
• Maintain high index of suspicion for treatable conditions – cerebral folate deficiency, mitochondrial disorders, and other metabolic conditions can present with autism symptoms but require specific treatment 8, 7.

Evidence Quality Note

The strongest guideline evidence comes from the American College of Medical Genetics (2013) and American Academy of Pediatrics recommendations synthesized in Praxis Medical Insights (2026), which provide the most recent and comprehensive guidance on laboratory evaluation in autism 8, 6, 7. The research evidence on vitamin D supplementation in autism, while promising, comes from smaller trials and requires larger validation studies 1, 5.