Table 5.
Tier-1 laboratory investigations for unexplained GDD/ID
| Blood* | Urine* |
|---|---|
| • Complete blood count | • Organic acids |
| • Glucose | • Creatine metabolites |
| • Blood gas | • Purines, pyrimidines |
| • Urea, creatinine | • Glycosaminoglycans |
| • Electrolytes (to calculate anion gap) | |
| • AST, ALT | |
| • TSH | |
| • Creatine kinase | |
| • Ammonia | |
| • Lactate | |
| • Amino acids | |
| • Acylcarnitine profile, carnitine (free and total) | |
| • Homocysteine | |
| • Copper, ceruloplasmin** | |
| • Biotinidase*** | |
| • Ferritin, vitamin B12 when dietary restriction or pica are present | |
| • Lead level when risk factors for exposure are present |
ALT Alanine aminotransferase; AST Aspartate aminotransferase; GDD Global developmental delay; ID Intellectual disability; TSH Thyroid-stimulating hormone.
*Perform testing after 4 h to 8 h of fasting. **Recommended tier-1 test in the TIDE protocol, but not by AAP, AAN. Consider as a first-line investigation when hepatomegaly, dystonia, abnormal liver function findings are present. ***Clinical expert recommendation only. Consider biotinidase testing when severe hypotonia, seizures are present.