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Pain Physician. 2011 May-Jun;14(3):259-70.

Comparative evaluation of the accuracy of benzodiazepine testing in chronic pain patients utilizing immunoassay with liquid chromatography tandem mass spectrometry (LC/MS/MS) of urine drug testing.

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Pain Management Center of Paducah, Paducah, KY 42003, USA.



Eradicating or appreciably limiting controlled prescription drug abuse, such as opioids and benzodiazepines, continues to be a challenge for clinicians, while providing needed, proper treatment. Detection of misuse and abuse is facilitated with urine drug testing (UDT). However, there are those who dispute UDT's diagnostic accuracy when done in the office (immunoassay) and claim that laboratory confirmation using liquid chromatography tandem mass spectrometry (LC/MS/MS) is required in each and every examination.


A diagnostic accuracy study of UDT.


The study was conducted in a tertiary referral center and interventional pain management practice in the United States.


Comparing UDT results of in-office immunoassay testing (the index test) with LC/MS/MS (the reference test).


A total of 1,000 consecutive patients were recruited to be participants. Along with demographic information, a urine sample was obtained from them. A nurse conducted the immunoassay testing at the interventional pain management practice location; a laboratory conducted the LC/MS/MS. All index test results were compared with the reference test results. The index test's efficiency (agreement) was calculated as were calculations for sensitivity, specificity, false-positive, and false-negative rates.


Approximately 36% of the specimens required confirmation. The index test's efficiency for prescribed benzodiazepines was 78.4%. Reference testing improved accuracy to 83.2%, a 19.6% increase, and 8.9% of participants were found to be taking non-prescribed benzodiazepines. The index test's false-positive rate for benzodiazepines use was 10.5% in patients receiving benzodiazepines.


This study was limited by its single-site location, its use of a single type of point of care (POC) kit, and reference testing being conducted by a single laboratory, as well as technical sponsorship.


Clinicians should feel comfortable conducting in-office UDT immunoassay testing. The present study shows that it is reliable, expedient, and fiscally sound for all involved. In-office immunoassay testing compares favorably with laboratory testing for benzodiazepines, offering both high specificity and agreement. However, clinicians should be vigilant and wary when interpreting results, weighing all factors involved in their decision.


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