INT-04 Drug Interferents

Manufacturers and clinical laboratories are doing a reasonably good job assessing endogenous interferents that may alter lab test results. The next big hurdle is the assessment of interference from common drugs. There are literally hundreds of drugs in clinical use, both prescription and over-the-counter, which can vary widely in their blood and urine concentrations and which can introduce errors in laboratory testing. Which are the most important to test? An expert panel was convened to make specific recommendations concerning the drugs and concentrations that should be assessed when validating laboratory tests.

Preparing concentrated drug solutions for interference testing has been labor intensive and expensive ̶ until now. Sun Diagnostics now offers ASSURANCE™ DRUG Interference Test Kit for Laboratory Use as part of interference testing procedures. Interferents available include: ACETAMINOPHEN, N-ACETYLCYSTEINE, ACETYLSALICYLIC ACID, AMPICILLIN SODIUM, CEFOXITIN SODIUM, CYCLOSPORINE, DOXYCYCLINE HCL, HEPARIN, IBUPROFEN, LEVODOPA, METHYLDOPA, METRONIDAZOLE, PHENYLBUTAZONE, RIFAMPICIN, and THEOPHYLLINE. Components may be purchased individually, in customer-defined combinations, or as INT-04 (one vial of each component).

Drug components and concentrations are based on recommendations by the expert panel1 and the Clinical Laboratory Standards Institute (CLSI).2 The concentrations are 20 times the recommended test concentrations, allowing a 1:20 dilution with serum/urine pool.


Interferents and Typical Values Table:

ASSURANCE™ Drug Interference Test Kit Simplifying Interference Testing for Drugs INT-04 contains 15 drugs as recommended by an expert panel1 as well as CLSI2
Interferent ASSURANCE™ Concentration Volume Per Vial Component Part Number Component Price
ACETYLCYSTEINE 204 mmol/L 1 mL INT-04ACC $100
AMPICILLIN NA 3,040 µmol/L 1 mL INT-04AMP $100
CEFOXITIN NA 30,920 µmol/L 1 mL INT-04CEF $100
DOXYCYCLINE HCL 1,350 µmol/L 1 mL INT-04DOX $100
THEOPHYLLINE 4,440 µmol/L 1 mL INT-04THE $100
LEVODOPA 400 mg/L 1 mL INT-04LEV $100
METHYLDOPA 400 mg/L 1 mL INT-04MED $100
METRONIDAZOLE 14,020 µmol/L 1 mL INT-04MET $100
IBUPROFEN 48,500 µmol/L 1 mL INT-04IBU $100
PHENYLBUTAZONE 8,000 mg/L 1 mL INT-04PHE $100
RIFAMPICIN 1,562 µmol/L 1 mL INT-04RIF $100
CYCLOSPORINE 100 mg/L 1 mL INT-04CYC $100
ACETAMINOPHEN 26,480 µmol/L 1 mL INT-04ACM $100
HEPARIN 60,000 U/L 1 mL INT-04HEP $100
ETHANOL 100% 1 mL INT-04E n/a
included with purchase of ethanolic interferents
ASSURANCE™ Drug Interference Test Kit
Includes 1 vial of each interferent
INT-04 $1100


1 Sonntag O, Scholer A. Drug interference in clinical chemistry: recommendations of drugs and their concentrations to be used in drug interference studies. Ann Clin Biochem 2001; 38:376-385.
2 Clinical and Laboratory Standards Institute (CLSI). Interference Testing in Clinical Chemistry; Approved Guideline ̶ Second Edition. CLSI document EP7-A2 (ISBN 1-56238-584-4). Clinical and Laboratory Standards Institute, 940 West Valley Road, Suite 1400, Wayne, Pennsylvania 19087-1898 USA, 2005.


  • INT-04 should not be used past the expiration date listed on the kit box. Refer to Interferent vials for expiration of individually purchased components or custom kit configurations.
  • If there is evidence of microbial contamination discard the vial.
  • This product is not intended for use as a control, standard or calibrator.
  • Information gathered from experiments performed using ASSURANCE™ Interference Test Kits should not be used to adjust patient results. Confirm results with an alternate method when necessary.

Items for Download:
INT-04 Package Insert
INT-04 Safety Data Sheet
Drug Interference Testing Protocol
Results Reporting and Data Analysis Spreadsheet – please email for spreadsheet.