The 7 unsung heroes of sample integrity according to a lab director
How does a lab deliver consistently safe, reliable results? Henk Ruven, a specialist in laboratory medicine at St Antonius Ziekenhuis, NL, illuminates the importance of a series of steps that are vital to sample integrity.
Correct order of draw
The order in which the various steps of blood collection take place is both crucial, and difficult to monitor. Blood collection tubes contain an additive that either accelerates clotting of the blood or an anticoagulant that prevents the blood from clotting. They come in a range of standardized colors to identify their purpose. Henk explains: “If the nurse doesn’t draw it in the correct order, you get hemolysis, where the red blood cells are broken, and the hemoglobin of the cell is released, freely floating in the tube. It completely voids the result. But we will only find this out after the patient has already left and the collection is ended.”
All tubes that contain additives need to be gently inverted according to the IFU - the act of agitating the tube to mix the additive with the blood. “With anticoagulants in particular, you have to mix it quickly. Otherwise, the coagulation process will begin and that's not what you want, it will void the result. Again, we’re seeking to avoid hemolysis.” says Henk.
Appropriate transport system
Samples may come from within or outside the hospital and require labelling, secure packaging and protection from fluctuating environmental factors. Henk describes how his laboratory receives samples:
“Within the hospital, we have pneumatic tube systems, but these are not appropriate for all samples as there is a risk of damage to the container and the blood cells. Outreach samples can come from small cities and small villages in the region and it can be difficult to protect the sample from the temperature, especially during a hot summer or a cold winter.”
Length of time a sample spends in transit
There is a relatively short window available to deliver a sample to the lab, even with secure and temperature-controlled transportation. “Blood samples have a short shelf life” says Henk. ”A blood sample collected via conventional blood draw methods cannot stay at room temperature for longer than eight hours. It can be difficult to keep the temperature within the established temperature ranges during transportation. Speed is of the essence here to avoid the degradation of a sample.”
“Accuracy is directly tied to the quality of your lab testing; the reliability of your values. As well as protecting against needlestick injuries, safety relates to the patient - if you do not produce reliable lab results, then the patient is not safe...
Every tube will have a nominal, indicated volume that needs to be filled. Henk gives one example of how a proper fill is achieved: “You have to put enough blood in a tube, up to a fill mark. Sometimes there can be a difficulty with, for example, the vein of a critically-ill patient; there’s no more blood coming out of their vein. It’s under-filled to maybe half or three quarters; there is a risk here of an unreliable result. So then you have to move the needle a little further back or a little more forward; an experienced phlebotomist will have these skills.”
Barcode labelling is an accurate method for electronically tracking and logging a patient's sample and analysis. And ever vigilant to the need to protect the patient, Henk cites an issue his lab experienced in the past: “Having the full name is vital. Let me provide an example; my name is Henk Ruven. Let’s pretend I have a twin named Herman Ruven. He is currently a patient in the hospital, and it goes through the electronic patient system, identified as “H Ruven'' and is then mistakenly allocated to me; the wrong patient record has been selected and Herman doesn’t receive the correct care.”
An electronic database that verifies the patient before creating printed barcoded labels will rule this out and ensure integrity across the whole process.
Proper collection devices
Henk is keen to emphasize the demands he and his team place upon their equipment: “Accuracy is directly tied to the quality of your lab testing; the reliability of your values. As well as protecting against needlestick injuries, safety relates to the patient - if you do not produce reliable lab results, then the patient is not safe, that is the understanding that governs all activity in the lab. And as professionals, we are conducting quality control tests on this equipment all the time, we are the experts - we know what we need and where improvements need to be made.”
And he wants to see a constant dialogue between manufacturers and users of their products: “Manufacturers need to provide white papers - they conduct their own research and also consult peer-reviewed literature then publish a white paper about their products and innovations. It tells us, as specialists, about the quality of their tubes and equipment and the quality of the analytical tests which are performed using these tools.”
Safety and value, it’s in our blood
Protecting patients, clinicians and accuracy are topics to be covered in more detail here in the coming months. To ensure you don’t miss out, subscribe to the series here.
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