Cobalt (Urine)

Diagnostic Use

Urine cobalt testing is preferred to assess occupational exposure in most cases. Blood cobalt is generally for assessment of possible toxicity related to metal-on-metal prostheses.

Cobalt related systemic toxicity is a complex clinical syndrome with variable organ involvement including haematological (e.g. polycythaemia), endocrine (e.g. thyroid), neurological (e.g. hearing, balance and visual disturbances) and cardiovascular (e.g. myocardial) dysfunctions.  Dose-response data and biokinetic modelling suggest blood Cobalt <5100 nmol/L (<300 ug/L) is unlikely to be associated with clinically relevant symptoms for healthy individuals. However, different disease states e.g. renal failure, iron deficiency, sepsis, malnutrition, alcoholism or medication intake can predispose to Cobalt-induced toxicity at much lower levels. At this stage, no consensus can be reached as to a threshold blood level above which toxic systemic effects will predictably arise and therapeutic measures to be undertaken (Ref. 1).

Urine Cobalt has a short biological half life and reflects recent exposure therefore samples should be taken at the end of the working shift at the end of the week. Refer to up-to-date WorkSafe standards for more information.

Interpretation

Cautions:

Gadolinium and Iodine are known to interfere with metal tests. If either Gadolinium- or Iodine-containing contrast media has been administered, a specimen should not be collected within 96 hours from the procedure.

As the concentration of Cobalt in plasma and urine are extremely low, specimen collection procedures require rigorous attention to clean specimen collection and handling procedures, to prevent contamination.

Reference Intervals

BEIs apply to samples collected at end of shift at end of work week.

From NZ WorkSafe: Workplace Exposure Standards and Biological Indices, 12th edition, November 2020.

For the latest Worksafe document click on the link below.

Conversion of units

nmol/L = ug/L x 17