Trace Element and Micronutrient Reference Laboratory
Scotland's specialised laboratory for trace elements and vitamins in health and disease
Protocol for Micronutrient Service
When assessing a patient's nutritional status his/her electrolytes, calcium, glucose, magnesium, protein/albumin and CRP should be measured.
The blood specimens should be sent to the laboratory promptly, accompanied by a request form appropriately filled and requesting a micronutrient screen (Monday to Thursday- between 9 am and 3.30 pm).
Effect of inflammatory response on micronutrientsThe systemic inflammatory response associated with acute injury or infection affects the concentrations of micronutrients in plasma independently of tissue stores. Low plasma levels therefore do not necessarily indicate deficiency and trace element or vitamin supplementation may not be warranted. Some micronutrients are unaffected by systemic inflammation. These are present predominantly in red cells.
The inflammatory status of the patient should be known or assessed (by measuring CRP) before requesting a micronutrient screen.
In patients with:
CRP levels <15 mg/l - plasma micronutrient concentrations fall less than 10% - laboratory assessment of micronutrient status is reliable.
CRP levels >15 <50 mg/l - plasma micronutrient concentrations fall by between 20-40% - laboratory assessment of micronutrient status is unlikely to be reliable and should be discouraged.
CRP levels >50 mg/l - plasma micronutrient concentrations fall by between 30-60% - laboratory assessment of micronutrient is of no value.
Micronutrient screening for patients on TPNBlood samples for micronutrient screening should be taken at least 3 hours after TPN infusion has been completed to allow micronutrients to distribute from the central compartment to tissues.
Micronutrient concentrations should be measured no more frequently than every 2-3 months in patients who are dependent on long term nutritional support.