What are the causes of false positive urine drug screens for cocaine?

From the Guidelines

False positive results for cocaine on urine drug screens can occur due to cross-reactivity with certain medications or substances, and confirmatory testing using more specific methods like gas chromatography-mass spectrometry (GC-MS) should be performed to avoid misinterpretation of results. When considering the potential causes of false positive urine drug screens for cocaine, it is essential to take into account the limitations of the selected matrix and potential cross-reactivity with unrelated substances in the urine, as noted in a study on testing for drugs of abuse in children and adolescents 1. Some key factors that may contribute to false positive results include:

• Cross-reactivity with certain medications, such as fluoroquinolone antibiotics, which have been reported to cross-react with immunoassay opiate screens 1
• Consumption of foods or substances that metabolize into compounds similar to cocaine metabolites
• Laboratory errors during sample collection, handling, or testing
• Lack of specificity in some immunoassay tests, which may react with compounds structurally similar to cocaine metabolites It is crucial for healthcare providers to be aware of these potential causes and to consider a patient's complete medical history, including prescribed medications, when interpreting drug test results 1. By understanding these factors and utilizing confirmatory testing when necessary, healthcare providers can minimize the risk of misinterpretation and ensure accurate results.

From the Research

Causes of False Positive Urine Drug Screens for Cocaine

• There are several potential causes of false positive urine drug screens for cocaine, including:
  • Cross-reactivity with other substances, such as certain medications or compounds found in food or environment 2
  • Interference from other analytes in the urine sample 2
  • Limitations of the immunoassay screening method, which can produce false positive results 3, 4
• Specific substances that have been investigated as potential causes of false positive urine drug screens for cocaine include:
  • Amoxicillin, which was found to be unlikely to produce false positive results in one study 5
  • Lidocaine, which was found not to produce false positive results in another study 6
• The use of confirmatory testing, such as gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-mass spectrometry (LC-MS), can help to identify false positive results and ensure accurate diagnosis and treatment 3, 4
• False positive urine drug screens for cocaine can have significant clinical implications, including delayed or inadequate pain management, and highlight the importance of confirmatory testing in clinical practice 3