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Blood testing in combination with urine drug testing can provide a complete picture of patient compliance

Urine drug testing remains the mainstay for identifying illicit or non-prescribed drug use for many reasons and is ideal for establishing recent drug exposure.^1-2 Urine drug concentrations are typically much higher than those in corresponding blood (serum) samples and consequently allow a longer window of detection than blood.^1-2 However, urine toxicology results cannot provide evidence of therapeutic effect and cannot be used to estimate dose.^1-2 Multiple variables associated with drug disposition in the body induce highly variable drug-metabolite concentrations from a given dose.

Variables include:

• Pharmacogenetics
• Metabolism
• Absorption and elimination rates
• Urinary pH
• State of hydration
• Drug formulation and co-administered medications³  

Simply put, the presence of a drug in the urine only indicates use in recent days. So although a patient may test positive for a prescribed medication, a urine drug test result cannot tell the physician if the patient has been taking more or less than prescribed.

Click here to read our Q&A with Pain Live on the differences between urine and blood testing.

Click here to learn more about AIT's blood testing services.

References 

1. Reisfeld GM, Salazar E, Bertholt RL. "Rational use and interpretation of urine drug testing in chronic opioid therapy." Annals of Clinical and Laboratory Science. 2007: 37(4): 301-314.
2. Katz NP, Sherburne S, Beach M, et al. "Behavorial monitoring and urine toxicology testing in patients receiving long-term opioid therapy." Anesthesia and Analgesia. 2003; 97(4): 1097-1102.
3. Gunn J and Schwilke E. "The Value of Blood Analysis for Compliance Monitoring." Pract Pain Manage 11.4 (2011): 16-18.