Introduction-
To understand pseudohypokalemia, we have to understand what hypokalemia is. Hypokalemia is a condition in which the amount of potassium in the blood decreases. Hypokalemia is caused by insufficient potassium ingestion, an increase in the removal of potassium from the body while vomiting, diarrhea, consuming certain medications, and by intake of certain medications, and faulty lab tests - pseudohypokalemia. Potassium is a mineral that helps properly function the muscles, nerves, and heart and keeps the blood pressure within the normal range. Pseudo hypokalemia is one of the causes of hypokalemia. ‘Pseudo’ means false, and ‘hypokalemia’ means a decreased level of potassium in the blood. It is a lab error while carrying out blood tests and not actual hypokalemia.
How Is Pseudohypokalemia Caused?
There is very little information about the mechanism that causes pseudohypokalemia. However, it is multifactorial. Once the blood sample is collected, it is sent to the laboratory for testing. In the lab, the sample is put into a centrifuge (a machine that separates the components of the blood). After the blood cells are separated from plasma or serum (the watery part of the blood), the serum is processed, and tests are done.
Pseudohypokalemia occurs due to:-
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Sampling Error- When there is a delay in the sample collection and processing time, the other metabolically active blood cells take up potassium from the surrounding fluid if the samples are kept at room temperature for longer periods. The most common example is Leukemia (a type of blood cancer). There are a large number of abnormal white blood cells in the blood sample of an individual. These abnormal cells tend to absorb potassium from the extracellular fluid (fluid outside the blood cells), causing pseudohypokalemia. The longer the blood serum is left with the blood cells, there is a high probability of a decrease in potassium levels. Lab testing is done in three phases- preanalytical, analytical, and post-analytical. Most of the errors occur in the pre-analytical phase, which relates to the collection and transportation of the sample from the source.
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Increase in Temperature- The surrounding temperature of the area also plays a huge role in developing pseudohypokalemia. It is found to increase during the summer season- seasonal pseudohypokalemia. Prolonged exposure of the blood sample to a higher than normal temperature stimulates the metabolism of glucose (blood sugar) thus increasing the uptake of potassium by the cells due to activation of the sodium-potassium exchange ATPase - an enzyme present on the outer surface of a cell that helps in maintaining a proper concentration of sodium and potassium ions within and outside of the cell. The activity of sodium-potassium exchange ATPase is increased by an increase in the temperature and presence of glucose. An increase in the temperature of the laboratories where the samples are kept can also lead to an error in potassium levels. An increase in temperature has a larger effect on potassium level concentration than transportation time.
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In a recent study, the intravenous administration of insulin (a hormone that controls blood sugar levels) has also been found to cause pseudohypokalemia.
How To Reduce Pseudohypokalemia?
Taking certain mindful steps can reduce the risk of pseudohypokalemia.
They are,
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The blood samples should be collected and transported in temperature-regulated vials (collection tubes) and air-conditioned vehicles.
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The time taken for the transportation of the samples to the lab should be reduced.
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Decreasing the time of centrifugation (separation of the blood components) and testing for potassium can help solve the issue.
Blood sample—----- 30 minutes -----centrifugation—----- 30 minutes ---processing
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The laboratories should reduce the TAT or turnaround time- the amount of time utilized to complete the procedure, to within an hour for a correct serum potassium estimation.
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Inhibitors that block the movement of potassium ions in and out of the cells can be added to the collection vials.
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Proper training should be provided to the non-technicians handling the lab equipment explaining to them the importance of time, temperature, and proper handling of the samples.
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Studies are being carried out to find out the approximate temperatures at which the blood cells release and take up potassium. This might help design suitable collection vials.
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Experiments being carried out with Ouabain (a compound that inhibits the sodium-potassium ATPase) have been shown to increase the level of potassium at 37 degrees centigrade in a hypokalemic sample.
Conclusion -
Pseudohypokalemia is a laboratory error and a reversible phenomenon, meaning it can be reversed under controlled temperature and time conditions. There is an increased incidence of pseudohypokalemia in summer, so tropical countries such as India should plan a timely collection, transportation, separation, and processing of blood sample to avoid errors in tests. False levels result in unnecessary diagnoses and faulty treatment plans that could be detrimental to the individuals. If an error in the blood report is suspected, a re-test should be scheduled for the betterment of the individual.
