Urine sample quality for cadmium monitoring

March 5, 1996

R.K. Skogerboe, Ph.D.
Director of Biomonitoring
Corning Clinical Laboratories
[Recipient address omitted]
Dear Dr. Skogerboe:

This is in response to your letter of February 29, regarding your questions about low urinary creatinine levels.

In general, in order for urine samples to be acceptable for analyses for cadmium in urine, (CdU) and Beta-2 microglobulin in urine (Beta-M), urine samples should be screened, by simple methods, prior to submitting the urine sample to the laboratory for more costly analyses. If a urine sample is too dilute (specific gravity less than 1.008) or too acidic (pH less than 5.5), another sample should be collected for analysis.

Regarding your clients' questions about low urinary creatinine levels (CRTU), OSHA specified a number of sample collection and handling procedures in Appendix F of the final cadmium standard to reduce the chance that Beta-M will degrade. Under Section 3.4.1, for example, employees are advised to void, drink a large glass of water, and then provide a urine specimen for analysis within an hour (29 CFR 42424). OSHA is of the opinion that, when standardizing urine samples to grams of CRTU, many of the low creatinine levels result from over-hydration.

OSHA recommends that employees provide a urine sample for CdU, Beta-M, and CRTU analyses without first drinking a glass of water. If that urine sample is too dilute (specific gravity less than 1.008), another sample should be collected at the next void with no intervening hydration. If the urine is too acidic (pH less than 5.5), the employee should drink no more than an 8-ounce glass of water; another sample should be collected after 1 hour; urine from that second void should be used for CdU, Beta-M, and CRTU analyses.

Samples that are too dilute or too acidic should not be submitted for urinalysis. If low CRTU levels persist, further evaluation of renal function is warranted to rule out other etiologies.

If you have any questions, please contact my office at 202 219-5003.

Sincerely,

Melissa DcDiarmid, MD, MPH
USDOL/OSHA Office of Occupational Medicine

Corning Clinical Laboratories
Biomonitoring Laboratory
[Recipient address omitted]

[Requester letter reproduced on OSHA page; omitted here.]