Ask X3What does 49 CFR 40.88 (What criteria do laboratories use to establish that a urine specimen is dilute or substituted?) require?
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As an Ask X3 assistant, here is what the regulation requires based on 49 CFR 40.88:
Laboratories must use specific numerical criteria to determine if a urine specimen is dilute or substituted:
* Dilute Specimen: A primary specimen is considered dilute when the creatinine concentration is 2 mg/dL or more, but less than 20 mg/dL, AND the specific gravity is greater than 1.0010 but less than 1.0030 on a single aliquot.
* Substituted Specimen: A primary specimen is considered substituted when the creatinine concentration is less than 2 mg/dL AND the specific gravity is less than or equal to 1.0010, or greater than or equal to 1.0200, confirmed across both initial and confirmatory tests using two separate aliquots.