Portable lactate analysers are continually evolving in order to improve the accuracy of their results and, above all, to minimise user-derived errors, mainly linked to the sampling process. Obtaining anomalous results in blood lactate analysis using portable analysers is in most cases related to the user’s own actions. This includes incorrect coding of the analyser in relation to the batch of test strips, incorrect maintenance of the test strips or sensors or their use beyond the expiry date, insufficient blood volume to fill the test strip reaction chamber, contamination of the blood sample with sweat, etc.
One of the advances of portable lactate analysers is the decrease in the volume of blood required for measurement, which has been reduced considerably. From the 20 microlitres of blood used by laboratory lactate analysers and even some portable lactate analysers based on photometry, the sample volume has been reduced and nowadays the latest generation of portable lactate analysers, whose method of analysis is electrochemical, require a smaller volume of blood, The electrochemical method of analysis requires a blood volume of 0.2 to 0.7 microlitres of blood (30 to 100 times less blood volume compared to Roche’s Accutrend Plus, which requires 15 to 50 microlitres of blood); This minimises errors due to insufficient blood volume for testing. This decrease in the volume of blood required for the analysis is a considerable advance, but it entails the added problem of sample contamination, in that any slight contamination of the blood by sweat, alcohol, etc., will lead to a reduction in the blood test results will lead to a decrease in the accuracy of the result and even an abnormal blood lactate result.
Sweat, for example, has a much higher lactate concentration than blood and can significantly alter the result of the measurement. Blood samples can also be contaminated by elements such as water, serum, alcohol, creams, fragrances etc.
It is essential to make sure that the area where we are going to take the blood sample from (the fingertip, the earlobe) has been cleaned properly. After making a puncture with a lancet, it is advisable to discard the first two drops of blood to ensure that there is no contamination in the sample.
A large percentage of mistaken results when performing a lactate analysis are due to errors when taking the blood sample. Therefore, it is very important to take the blood sample correctly in order to ensure that accurate results are obtained.
The Lactate Plus and Lactate Scout, both have control solutions that are used to rule out possible failures in the analysers. In cases in which the results obtained may seem atypical, we would use the control solution instead of blood to perform a measurement with the portable lactate analyser. If the values shown by the analyser are between the values indicated in the control solution, it means that the analyser is functioning properly. In these cases, we should check that the test strips are not expired, that they have been stored under optimal conditions and that the sampling procedure has been followed correctly.
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