Handling Blood Samples for Mineral Testing
Minerals are very stable in blood or blood serum. For serum mineral analysis the most important consideration is to remove the clot from the serum in a timely manner (see below for details). Blood serum for mineral analysis does not have to be shipped on ice, but should be protected from extreme heat.
Whole blood samples for mineral analysis (toxic elements and/or selenium) should be collected into tubes with anticoagulant and shipped on ice by overnight courier. Failure to do so may result in the sample becoming clotted, which will affect the analytical results.
Separate the Serum from the Clot when Submitting Serum Samples
The most common sample handling mistake leading to invalid mineral results is leaving the clot in contact with the serum too long. Mineral concentrations within the red cells are different from those in the serum.
With prolonged contact after sample collection, the red cells begin to die and minerals begin to equilibrate across the cell membrane. This especially leads to artificially high serum concentrations of potassium and phosphorus, and potentially to artificially high concentrations of selenium and manganese. Optimally, the clot should be separated from the serum within four hours of sample collection.
Handling Blood Samples for Vitamin E or Vitamin A Testing
Again, it is important to separate the serum from the clot.
There are some popular misconceptions about the requirements of shipping serum for vitamin testing, especially vitamin E testing. Both vitamins A and E are stable enough that accurate assessment of original serum concentrations can be achieved with samples that have been shipped via overnight courier services.
Samples for vitamin A or E determination should be protected from prolonged exposure to direct sunlight. They should be packed and shipped with ice in insulated shipping containers. It is not necessary that the samples be frozen initially, or that they arrive frozen at the laboratory, although freezing does not harm the samples.
Liver Biopsy Samples versus Serum Samples for Assessment of Trace Mineral Nutritional Status
Liver biopsy samples are an especially good means of assessing copper status. They are also very useful in assessing selenium status, but not necessarily better than serum samples. We can measure trace mineral concentrations in very small liver biopsy samples that can be quickly, safely, and easily taken using a “Tru-Cut” type biopsy instrument. Please see Liver Biopsy Procedure in Cattle for instructions.