Clinical Lab Handbook

Container/Tube: SST (Protect from light)

Alternate Specimen: Red Top (Protect from light)

Specimen Volume: 5 mL of serum

Collection Instructions: Allow specimen to clot for 30 minutes. Spin specimen in centrifuge.

Centrifuge specimens and remove the serum from the cellular material within 4 hours of collection.

Protect the sample from light.

Enzyme-Multiplied Immunoassay Technique (EMIT®)

The VITROS VANC Reagent is a dual chambered package containing ready-to-use liquid reagents that are used in a twostep reaction to quantitatively measure vancomycin. Test sample is added to Reagent 1 containing vancomycin labeled with glucose-6-phosphate dehydrogenase (G6P-DH), followed by Reagent 2 containing antibody reactive to vancomycin, glucose-6-phosphate and nicotinamide adenine dinucleotide (NAD). The assay is based on competition between vancomycin in the sample and vancomycin labeled with G6P-DH for antibody binding sites. G6P-DH activity decreases upon binding to the antibody, so vancomycin concentration in the sample can be measured in terms of G6P-DH activity. G6P-DH converts NAD+ to NADH, resulting in an absorbance change that is measured spectrophotometrically at 340 nm. Endogenous serum G6P-DH does not participate in the reaction since NAD+ functions only with the bacterial (Leuconostoc mesenteroides) enzyme conjugate employed in the assay.

Vancomycin is used in the treatment of serious or severe infections caused by gram-positive organisms resistant to penicillins, cephalosporins, or other antimicrobial agents. It is also used in the treatment of antibiotic-associated pseudomembranous colitis produced by Clostridium difficile. The risk of ototoxicity and nephrotoxicity is increased in patients with impaired renal function, and in patients receiving concurrent aminoglycoside treatment. Serum vancomycin measurements are used in the diagnosis and treatment of vancomycin overdose and in monitoring levels of vancomycin to ensure appropriate therapy.

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1. Pharmacokinetic factors including dosage form, mode of administration, co-administered drugs, age, renal function, and individual variations in adsorption, distribution, and excretion can influence the appropriate time of sample collection following administration of vancomycin.
2. Trough drug monitoring should begin after steady state is achieved and samples should be collected within 30 minutes of the next dose.
3. When peak levels are being measured, samples should be drawn 0.5–2 hours after an infusion.