Standard Interpretations - Table of Contents Standard Interpretations - Table of Contents
• Standard Number: 1910.1027

March 5, 1996

R.K. Skogerboe, Ph.D.
Director of Biomonitoring
Corning Clinical Laboratories
363 West Drake Road, Suite 8
Fort Collins, CO 80526

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
200 Constitution Avenue, NW.
Washington, DC 20210




Corning Clinical Laboratories
Biomonitoring Laboratory
363 West Drake Road, Suite 8
Fort Collins, CO 80526

February 29, 1996

Ms. Caroline Freeman
Office Director
Health Standards Program
Room N3718, USDOL-OSHA
200 Constitution Avenue, NW.
Washington, DC 20210

Dear Ms. Freeman,

Per our phone discussion of this date, I am writing to explain a problem associated with testing urine for Cadmium and Beta-2-Microglobulin and to request the advice of your office in ameliorating this problem.

As you are aware, a significant percentage of urine specimens received exhibit abnormally low creatinine concentrations while the Cd or B-2-M levels are typically within normal ranges in terms of non-normalized concentrations. However, normalization to creatinine often results in ''artificially'' elevated velure that exceed the defined cutoffs. Many of our clients react by entering notations in the patients' file and retest within 2 weeks. In our experience, all of the retests have produced values within the acceptable ranges. As I told you, this problem is particularly operative for women. Our analysis indicates that nominally 28% of the women and 5% of the men exhibit levels below 0.3 gm/L.

Our clients frequently request advice on approaches for screening urine specimens with low creatinine levels to avoid submitting "abnormal" samples and to preclude the need for retesting. We cannot respond without OSHA approval. Data that we have developed indicate that creatinine levels can be correlated to urine specific gravity and that the correlation coefficient is 0.88. This suggests that using specific gravity to screen potentially "abnormal" specimens is probably a viable approach.

If there is a screening approach acceptable to your office, we would appreciate receiving formal notification to that effect together with any specific criteria and/or operational details.

Per our discussion about differences in the creatinine distributions for women and men, I will prepare a data summary and evaluation to be sent to you next week. Thank you for your guidance in dealing with this matter.

Sincerely,



R. K. Skogerboe, Ph.D.
Director of Biomonitoring
Fax 970 226-0712


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