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|Test Update Information||Theophylline assay changed from the Abbott Axsym method to the Beckman DxC method on 6/25/2012.|
|Performed by||Parnassus & Mission Bay Chemistry|
|In House Availability||Test available 24 hours per day 7 days per week|
|Method||Turbidimetric inhibition immunoassay (Beckman DxC800)|
|Collection Instructions||Time to steady state: highly variable 3-4 days (adults) or 3 doses
Indicate date and time of draw on requisition.
|Container type||Gold top or Light Green top|
|Amount to Collect||1 mL blood|
|Sample type||Serum or plasma|
|Preferred volume||0.5 mL serum or plasma|
|Min. Volume||0.2 mL serum or plasma|
|Critical value||> 30 mg/L|
|Stability||Room temperature 8 hours, refrigerated 2 days, frozen 1 week|
|Turn around times||STAT 1 hour, Routine 4 hours|
|Additional information||According to the UpToDate guidelines (accessed May 21, 2012) on "Theophylline use in asthma" by Hendeles and Weinberger, MD, "The efficacy and toxicity of theophylline are closely related to the PEAK serum concentration. In patients receiving theophylline monotherapy, doses providing a PEAK serum concentration of 10 to 20 mg/L (mcg/mL) are best documented to improve symptoms and reduce the need for rescue therapy. However, bronchodilatory, antiinflammatory, and immunomodulatory effects of this drug are detectable at levels as low as 5 mg/L; in addition, serum concentrations of 5 to 10 mg/L may be adequate for some patients, particularly if they are also receiving inhaled glucocorticoids." These authors also state that they "recommend titrating dosage to a PEAK concentration of 10 to 15 mg/L with a theophylline formulation and dosing interval that will not result in large fluctuations between the peak and trough levels. A widely quoted guideline recommends a target serum concentration of 5 to 15 mg/L, but does not specify whether this should be a peak or trough level. Such a distinction is important because fluctuations in serum concentration can be sufficient for a trough concentration in the 5 to 15 mg/L range to result in a peak above 20 mg/L and consequent toxicity."
Note: The presence of human anti-mouse antibodies or heterophile antibodies may interfere with the theophylline assay in some cases. Testing for theophylline levels in parallel dilution studies and with a different assay may be useful in cases where interference by a monoclonal protein or abnormal immunoglobulin is suspected.
Click here for: A Guide on Drug Level Monitoring
|Last Updated||6/21/2016 14:00:24|