What does dilution mean?
A dilute specimen is a urine specimen with creatinine (muscle waste from everyday activity) and specific gravity (ratio of the density) values that are lower than expected but are still within the physiologically producible ranges of human urine. Creatinine and specific gravity are tested at the lab to identify invalid, dilute, or substituted specimens.
Will a recollection be necessary if the result is dilute?
How to proceed if the result is dilute:
- Negative dilute & HHS testing authority: Send the donor in for a recollection. If the donor has two negative dilute specimens within 30 days, the Medical Review Officer verifies and reports the second specimen as negative. Contact the MRO if the recollection does not have the dilution removed (see UrMG Section 13.5(b)(1)).
- Negative dilute & DOT testing authority: Send in for a recollection if the Medical Review Officer requests or your Agency policy requires (see 49 CFR 40.197). It must be a direct observed recollection. DOT 40.155 requires the MRO to verify and report the second specimen as negative-dilute.
- Positive dilute: Act on the positive result with no recollection needed.
Does a dilute result mean the donor is trying to cheat the test?
Dilution does not necessarily mean the donor is trying to cheat.
- Abnormal levels of urine creatinine may result from excessive fluid intake, glomerulonephritis, pyelonephritis, reduced renal blood flow, renal failure, myasthenia gravis, or a high meat diet.
- Increased urine specific gravity values may result from dehydration, diarrhea, excessive sweating, glucosuria, heart failure, proteinuria, renal arterial stenosis, vomiting, and water restriction.