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HelpTest Code PHNT Phenytoin
Laboratory Code
LAB31
Specimen Requirements
Submit only one of the following:
Preferred
Specimen Type: Serum
Container/Tube: Gold Top (SSTII)
Volume: 5.0 mL
Minimum Volume: 0.5 mL serum
Collection Instructions: Allow specimen to clot for 30 mins and centrifuge within 2 hrs.
Acceptable
Specimen Type: Plasma
Container/Tube: Green Top (Li Heparin/PST)
Volume: 4.5 mL
Minimum Volume: 0.5 mL plasma
Collection Instructions: Centrifuge within 2 hrs.
Specimen Stability
| Specimen Type | Serum/Plasma |
|---|---|
| Ambient | 2 days |
| Refrigerate | 1 month |
| Frozen | 5 months |
Methodology
Enzyme Immunoassay
Days and Times Performed
24 hrs, TAT 1 day
Specimen Condition
| Haemolysis | OK |
|---|---|
| Icterus | OK |
| Lipaemia | OK |
| Others | Not applicable |
Reference Interval
| Therapeutic range | 10 – 20 mg/L |
|---|---|
| Critical value | > 20 mg/L |
Testing Laboratory
National University Hospital
Clinical Chemistry, 67724346
Useful For
Therapeutic drug monitoring.
Service Code
31822
LOINC Code Information
3968-5
Alias
Dilantin
Update
Last updated 12/03/2025