Development and Evaluation of Inductively-Coupled Plasma Mass Spectrometry Methods for the Quantitation of Selenium in Erythrocytes, and Other Trace Elements in Patient Samples


Lay Abstract: The term “trace elements” refers to elements such as iron, copper, zinc, and selenium, which are present in the human body in tiny quantities (each making up less than 0.01% of total body weight). Certain trace elements are required for normal bodily function, and most can be harmful if present in large amounts. Hence, being able to measure whether a patient has too little (deficiency), enough (healthy), or too much (toxic), of these trace elements, is important for diagnosing patients who show symptoms of toxicity or deficiency.

Iron, copper, zinc, and selenium are normally measured in urine and serum (the liquid part of blood that is left after you remove the cells). At Charing Cross Hospital, urine and serum are measured in separate batches, using a machine called a mass spectrometer. This is because urine and serum are tested under different conditions. It would be more efficient if we could test both urine and serum in a single batch under the same conditions, and we have devised a new set of conditions which we think will allow us to do this. Implementing this method was the first part of this project.

The second part of this project was to see if this method can also be used to measure selenium inside red blood cells, as opposed to serum. This is useful because measurement of selenium in serum can be disrupted by short-term events such as infections. This means that in certain cases a measurement of selenium might not be a true reflection of the amount of selenium you normally have in your body. Accumulation of selenium inside your red blood cells, on the other hand, is a long-term process, and so is less affected by short-term events, and is more reliable than measuring it in serum. This is already being done at a hospital in Glasgow. We want to start using the same method used in Glasgow to provide more accurate selenium measurements.

We need to make sure that these methods correctly measure the amount of trace elements, so we know that they are safe before we start using them for real patients. We will do this using “external quality assurance” samples that an independent body regularly sends to laboratories like ours to check our performance. We know how much of each trace element should be in these samples, so we can check whether our methods work correctly or not by using them to measure iron, copper, zinc, and selenium in these samples and comparing our result to the expected result. If they work well enough, we can use them instead of the current methods, meaning the laboratory will be more efficient and measure selenium more accurately