Thiocyanate, Serum (THIOCY)

Test Code

Quest Code

Alias/See Also

CPT Codes

Preferred Specimen
3 mL serum collected in a no additive (red-top) tube

Minimum Volume
1.5 mL

Other Acceptable Specimens
Serum collected in: No additive (dark blue-top) tube • Plasma collected in: EDTA (lavender-top) or EDTA (dark blue-top) tube


Centrifuge and immediately separate serum or plasma specimens from the cells into transport tube

Transport Container
Transport tube

Transport Temperature
Room temperature

Specimen Stability
Room temperature: 72 hours
Refrigerated: 14 days
Frozen: 30 days

Colorimetric (C)

Setup Schedule
Monday, wednesday and friday

Clinical Significance
Thiocyanate is used as a biomarker for exposure to cyanides or cyanide-containing chemicals. This test is a serum-based assay that is primarily used to monitor cyanide levels in individuals receiving sodium nitroprusside infusion therapy for treatment of extreme hypertension. It can also be used to determine cyanide levels in individuals who have been exposed to certain industrial chemicals, cigarettes, or thiocyanate-containing foods [1].

Thiocyanate is a principal metabolite of cyanide, which accumulates in the blood and urine in response to cyanide exposure, cigarette smoking, industrial chemicals, and sodium nitroprusside infusion. Some industrial chemicals associated with increased thiocyanate levels include acetonitrile, acrylonitrile, and amygdalin. Symptoms of thiocyanate toxicity include confusion, hyperreflexia, convulsions, and metabolic acidosis [1].

This test may be helpful for patients, with normal renal function who are receiving long-term nitroprusside therapy for 7 days or more, as well as patients with renal insufficiency who are receiving nitroprusside therapy for any length of time. Patients with renal insufficiency are especially at risk for cyanide toxicity [2].

Note that the following drugs elevate thiocyanate and could interfere with test accuracy: antipyrine, acetoacetate, and phenacetin (and their sulfoxides in large concentrations); phenacetin and acetaminophen; and salicylic acid and its complexes.

1. Riedel K, et al. Thiocyanate in plasma and saliva (Biomonitoring Methods, 2013). In: Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area of the DFG, ed. The MAK-Collection for Occupational Health and Safety: Annual Thresholds and Classifications for the Workplace. Wiley-VHCA AG: Zurich, Switzerland; 2013;13:277-292.
2. Schulz Y. Clin Pharmacokinet.1984;9:239-251.

Performing Laboratory
Quest Diagnostics Nichols Institute-Chantilly VA
14225 Newbrook Drive
Chantilly, VA 20151-2228

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.