Falsely Undetectable Vancomycin Levels in a Pediatric Patient With Chronic Granulomatous Disease

Area of Science:

• Clinical Chemistry
• Pharmacokinetics
• Pediatric Nephrology

Background:

• Vancomycin is crucial for treating infections in immunocompromised children, such as those with chronic granulomatous disease.
• Therapeutic drug monitoring of vancomycin trough levels is essential for efficacy and safety.
• Assay interference can lead to inaccurate drug level measurements.

Purpose of the Study:

• To report a case of erroneously low vancomycin trough levels in a pediatric patient.
• To identify the cause of the inaccurate drug measurements.
• To highlight the importance of laboratory method validation in therapeutic drug monitoring.

Main Methods:

• A child with chronic granulomatous disease receiving vancomycin treatment had trough levels monitored.
• Drug levels were initially measured using a particle-enhanced turbidometric inhibition assay.
• An alternative laboratory method was used for comparison and confirmation.

Main Results:

• The initial laboratory assay reported undetectable vancomycin trough levels.
• An alternative laboratory method confirmed therapeutic vancomycin trough levels.
• The discrepancy was attributed to interference with the initial assay method.

Conclusions:

• Erroneously low vancomycin trough levels can result from specific laboratory assay limitations.
• Prompt recognition and resolution of assay interference are critical to prevent inappropriate vancomycin dose adjustments.
• Accurate therapeutic drug monitoring is vital to avoid suboptimal treatment and potential adverse events like acute kidney injury.