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HelpMayo Test ID CAFF Caffeine, Serum
Specimen Required
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Collection Container/Tube:
Preferred: Serum gel
Acceptable: Red top
Submission Container/Tube: Plastic vial
Specimen Volume: 0.5 mL
Collection Instructions:
1. Serum gel tubes should be centrifuged within 2 hours of collection.
2. Red-top tubes should be centrifuged and the serum aliquoted into a plastic vial within 2 hours of collection.
Useful For
Monitoring caffeine therapy in neonates
Assessing caffeine toxicity in neonates
Method Name
Enzyme Multiplied Immunoassay Technique (EMIT)
Reporting Name
Caffeine, SSpecimen Type
SerumSpecimen Minimum Volume
0.25 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum | Frozen (preferred) | 28 days | |
| Ambient | 72 hours | ||
| Refrigerated | 72 hours |
Reject Due To
| Gross hemolysis | Reject |
Clinical Information
Caffeine is used to treat apnea of prematurity that occurs in newborn infants, the most frequent complication seen in the neonatal nursery.
In neonates, caffeine has a half-life that ranges from approximately 3 to 4 days, which is much longer than in adults (typically 4-6 hours) due to the immaturity of the neonatal liver. This requires that small doses be administered at much longer intervals than would be predicted based on adult pharmacokinetics.
The volume of distribution of caffeine is 0.8 to 0.9 L/kg (infants) or 0.6 L/kg (adults) and the drug is approximately 36% protein bound.
Toxicity observed in neonates is characterized by central nervous system and skeletal muscle stimulation and bradycardia. These symptoms are seen in adults at lower levels than in neonates, suggesting that neonates have much greater tolerance to the drug.
Reference Values
Therapeutic: 8.0-20.0 mcg/mL
Critical value: ≥30.0 mcg/mL
Interpretation
Optimal pharmacologic response occurs when the serum level is in the range of 8.0 to 20.0 mcg/mL.
Toxicity in neonates and adults may be seen when the serum level is above 20.0 mcg/mL.
Cautions
This assay is not intended to detect levels in adults.
Clinical Reference
1. Milone MC, Shaw LM. Therapeutic drugs and their management. In: Rifai N, Chiu RWK, Young I, Burnham C-AD, Wittwer CT, eds. Tietz Textbook of Laboratory Medicine. 7th ed. Elsevier; 2023:420-453.e9
2. Brunton LL, Knollmann BC, eds. Goodman & Gilman's: The Pharmacological Basis of Therapeutics. 14th ed. McGraw-Hill Education; 2023
3. Ou CN, Frawley VL. Concurrent measurement of theophylline and caffeine in neonates by an interference-free liquid-chromatographic method. Clin Chem. 1983;29:1934-1936
Method Description
The enzyme-multiplied immunoassay technique assay is a homogeneous enzyme immunoassay technique used for the analysis of specific compounds in biological fluids. The assay is based on competition between drug in the sample and drug labeled with the enzyme glucose-6-phosphate dehydrogenase (G6PD) for antibody binding sites. Enzyme activity decreases upon binding to the antibody, so the drug concentration in the sample can be measured in terms of enzyme activity. Active enzyme converts oxidized nicotinamide adenine dinucleotide (NAD) to NADH, resulting in an absorbance change that can be measured spectrophotometrically. Endogenous serum G6PD does not interfere because the coenzyme functions only with the bacterial (Leuconostoc mesenteroides) enzyme employed in the assay.(Package insert: Caffeine Reagent. Seimens Healthcare Diagnostics, Ltd; 03/2015)
Day(s) Performed
Monday through Saturday
Report Available
Same day/1 to 2 daysSpecimen Retention Time
2 weeksPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
80155
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| CAFF | Caffeine, S | In Process |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 8754 | Caffeine, S | 3422-3 |