Theophylline Drug Level
Label Mnemonic: THEO
Epic Lab Code: LAB35
Downtime Form: A-1a Therapeutic Drug Assay Requisition
Chemistry
6240 RCP
356-3527
Specimen(s):
Plasma
Collection Medium:
Plasma Separator Tube 4.5 mL
Alternate Collection Media:
Call laboratory for additional acceptable specimen collection containers.
Minimum:
3 mL whole blood in light green top tube or ONE Microtainer®.
Testing Schedule:
24 hrs/day, 7 days a week, including holidays.
Turn Around Time:
1 hour (upon receipt in laboratory)
Reference Range:
10-20 μg/mL Critical value: >20.0 μg/mL
Test Limitations:
Criterion: recovery within plus or minus 10% of initial value at theophylline levels of approximately 5 and 15 μg/mL. Icterus: No significant interference from bilirubin up to an I index of 50 (approximate bilirubin concentration: 50 mg/dL). Hemolysis: No significant interference from hemoglobin up to an H index of 1000 (approximate hemoglobin concentration: 1000 mg/dL). Lipemia (Intralipid): No significant interference up to an L index of 300 (approximate triglycerides concentration: 600 mg/dL). There is poor correlation between turbidity and triglycerides concentration. No significant interference from total protein up to 12 g/dL or rheumatoid factor up to 100 IU/mL. Due to cross-reactivity to 1,3 dimethyluric acid, this assay should not be used to quantitate samples from uremic patients (1-2). The incidence of patients with antibodies to E. coli beta- galactosidase is extremely low. However, some samples containing such antibodies can result in artificially high theophylline results that do not fit the clinical profile. As with any assay employing mouse antibodies, the possibility exists for interference by human anti-mouse antibodies (HAMA) in the sample, which could cause falsely elevated results. References: (1) Breiner R, McComb, Lewis S and Wong SHY, Marzouk N and Kapke GF. Positive interference with immunoassay of theophylline in serum of uremics, letters to the editor. Clin Chem. 1985;31:1575-1577. (2) Nelson KM, Mathews SE, Bowers LD. Theophylline concentrations may be falsely high in serum of uremic patients, letters to the editors. Clin Chem. 1983;29:2125-2126.
Methodology:
Kinetic Interaction of Microparticles in Solution (KIMS)
CPT Code:
80198
 
See Additional Information:
Chemistry Critical Lab Values