The result of a drug test for a urine specimen that contains an unidentified adulterant or an unidentified interfering substance, has abnormal physical characteristics, or has an endogenous substance at an abnormal concentration that prevents the laboratory from completing or obtaining a valid drug test result. There can be several reasons for an invalid or unsuitable result.
Examples include:
- Not suitable for testing
- pH is out of range
- Temperature of the specimen is out of range
- GC/MS interference
- Immunoassay interference
- Interfering substance
- Bottle A and B have different physical characteristics
- Creatinine < or = 5 but the specific gravity is within normal limits