Sample stability:
-
4 days at 15-25 o C
-
4 days at 2-8 o C
-
1-2 months at -20 o C
External Referrers: Please separate plasma/serum, freeze at -20 o C and transport frozen on ice.
The quoted therapeutic range is for trough concentrations; specimens should be collected shortly before administering the next dose of the drug.
Units : umol/L
Therapeutic interval : 40 - 80
Uncertainty of Measurement: 10%
Principle: Immunoturbidometric assay
Reagents: Roche TDM Phenytoin kit
Analyser: Cobas c502
Adjustment of therapeutic interval in hypoalbuminemia:
Phenytoin is strongly (approx. 90%) bound to albumin. This test measures total phenytoin.
Free phenytoin is the active fraction, but cannot be measured at Labplus.
The therapeutic range given above assumes the patient has a normal serum albumin concentration. In patients with hypoalbuminaemia, a proportionally lower therapeutic range is appropriate, and toxicity may occur at lower drug concentrations.
Approximate therapeutic intervals for hypoalbuminemic patients:
Plasma albumin 30 g/L: 30 - 60 umol/L
Plasma albumin 20 g/L: 20 - 40 umol/L
The chemical pathology team can be reached via email: chemicalpathologist@adhb.govt.nz or via Lablink (09) 307 4949 ext 22000 or 09-3078995
Emails will receive priority attention from the on-call chemical pathologist. Include the patients NHI.
After-hours: contact Lablink (Auckland City Hospital ext. 22000 or 09-3078995) or hospital operator for on duty staff after hours .
- Dr Samarina Musaad (Clinical Lead) : SamarinaM@adhb.govt.nz ext. 22402
- Dr Cam Kyle : CampbellK@adhb.govt.nz ext 22052
- Dr Weldon Chiu : WeldonC@adhb.govt.nz ext. 23427
- Dr Campbell Heron : CHeron@adhb.govt.nz ext. 23427
- Dr Sakunthala Jayasinghe Saku.Jayasinghe@adhb.govt.nz
- Dr Owen Yi WenyiYi@adhb.govt.nz