Fentanyl Screen Panel, Urine

Test performed  in these BACL Chemistry Labs
West Roxbury -Contact Jonathan Dryjowicz-Burek  857-203-5418
Bedford - Contact Rita Rocha 781-687-2603

FENTANYL SCREEN PANEL

Chemistry

Fentanyl, pH, Creatinine and Specific gravity

urine

refrigerated

1 week refrigerated

24/7

TAT 1- 3 days

Analyte	Reference range
Fentanyl	Negative
pH	4 - 10
Specific gravity	1.003 - 1.020
Creatinine	>20 mg/dL

With the increase in the importance of fentanyl as a common drug of abuse, some VISN laboratories are implementing in-house fentanyl screening tests. 
Our VISN laboratories perform in-house drug of abuse screen testing using immunoassays. These immunoassays, which most commonly are sensitive for classes of drugs (e.g. benzodiazepines, opiates) are inherently prone to cross-reactions and detection of a class of similar molecules.  For that reason confirmatory testing is frequently performed, using either GC/MS or LC/MS methods.  While highly sensitive and specific, confirmatory testing typically detects only specific molecules within a class of drugs; e.g. fentanyl itself, not similar drugs.
The new Fentanyl screening test has a cutoff value for positives at 1 ng/ml. 
Our current reference laboratory’s confirmatory test detects only fentanyl and its major metabolite, norfentanyl.  While validating the new screening test, we found a significant number of samples (roughly 10%) within our population of patients (all of whom had urine sent for fentanyl testing) with positive screening tests, but with no fentanyl on confirmation.  On further testing, some of these samples contained a currently-popular ‘designer’ drug, acetylfentanyl; others did not, but another fentanyl derivative cannot be ruled-out.  Testing of 40 urines from outpatients, not in drug treatment, had no positives. 
The most likely explanation of these results is that the fentanyl screen in some cases detects fentanyl derivatives not covered by our confirmatory testing procedures.  A more recent package insert also indicates that the screening test detects the ‘designer’ drug carfentanil, which is not routinely confirmed.  Providers are encouraged to order confirmatory testing for screening tests when clinically indicated, but should be aware that in the case of fentanyl and novel derivatives, our screening test detects molecules not yet detected by confirmatory methods. 
Reporting:

1. Fentanyl screens will be reported with comment:
   Effective Dec. 5, 2018 Fentanyl cutoff is 1 ng/mL. Fentanyl screen detects fentanyl derivatives not detected by confirmatory testing. Medications such as Trazadone can interfere and give false positive results. Interpret results in clinical context. 
2. Results with vaues between 1 and 2 ng/mL will be sent out for confirmation.
3. Effective 8/30/21 samples with results greater than 2 ng/mL will not be sent out for confirmation. Providers will still be able to request confirmation testing on any specimens that are not reflexed via the DAU confirmation menu in CPRS.