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Specimen Collection Manual and Test Catalog

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PHENYTOIN, FREE LEVEL

Geisinger Epic Procedure Code:  LAB2843    Geisinger Epic ID:  6357

SPECIMEN COLLECTION
Specimen type: 

Serum


Preferred collection container: 
Alternate collection container: 
3.5 mL gold-top (serum separator) tube
Specimen required: 

4 mL aliquot of serum ; minimum 2 mL


Patient preparation: 

Trough level: Immediately before next dose. 
Peak level: Two (2) hours after IV push, eight (8) hours after oral suspension.



SPECIMEN PROCESSING
Processing instructions: 

Allow serum to clot. Centrifuge to separate serum within 2 hours of collection. Serum collected in serum separator tubes must be aliquoted within 24 hours of collection.


Transport temperature: 

Frozen.


Specimen stability: 

Refrigerated: 24 hours. Frozen: 1 month.


Rejection criteria: 

Stability limits exceeded.



TEST DETAILS
Reference interval: 

Therapeutic Range: 1.0 - 2.0 ug/mL.


Critical values/courtesy alerts: 
> or = 3.0 ug/mL
CPT code(s):  80186
Note: The billing party has sole responsibility for CPT coding.  Any questions regarding coding should be directed to the payer being billed.
The CPT codes provided by GML are based on AMA guidelines and are for informational purposes only.

Test includes: 

Phenytoin, free.


Methodology: 
Immunoassay
Synonyms: 

Dilantin, Unbound or Free; Free Dilantin; Free Phenytoin; Phenytoin Free; Phenytoin Unbound; PHNYUB; Unbound phenytoin


Clinical significance: 

Phenytoin is an anticonvulsant hydantoin used for the treatment of generalized grand mal and complex partial seizures. Phenytoin is also used in neurosurgical procedures. Phenytoin levels are monitored to assure adequate theraepeutic levels are achieved and to avoid toxicity.


Doctoral Director(s): 
Hoi-Ying Elsie Yu, PhD, DABCC, FADLM
Sheng-Ying (Margaret) Lo, PhD, DABCC
Review Date:  12/17/2024

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