Interference in laboratory results can be a huge problem. Further complicating matters, there can be at least four reasons that interference occurs. Understanding why and how it happens is the first step in reading results correctly so that you can make an accurate diagnosis.
All blood specimens received by labs may be inappropriate for analysis because of hemoglobin. While it can occur in patients of all age groups, it is a particular problem when doing in vitro lab work. One of the questions that you should ask when evaluating referral laboratories is their rate of hemoglobin fails because while the national average is about 3.3%, some labs have rates as high as 15%. When lab work is analyzed, if the worker and equipment have not spotted hemoglobin and left the sample unanalyzed, you can see alarming rates up to 150% too high on many different items in a CBC. Levels of potassium and lactate dehydrogenase can be particularly problematic.
Bilirubin interference can cause you not to treat patients correctly based on their lab results. Different labs have their procedure when they receive a sample with a total bilirubin level lower than 15 milligrams per deciliter. Some labs attach a note saying sample icteric while others refuse to release the results at all. Some labs can dilute out the interference so that you get an accurate report. When sample dilution must occur, it is vital that the lab or the doctor multiple the results back by the dilution level so that correct numbers are obtained. Getting an accurate report is essential in many circumstances, but it is particularly critical in jaundiced babies or patients where the kidneys may no longer be functioning correctly.
Large lipid particles, like lipoproteins and chylomicrons, can cause real issues in lab work. They can lengthen drastically the amount of time that it takes the blood to clot. Some instruments used in labs will not report a time if too long passes without the blood clotting. Other devices will report a time if the results can be duplicated within a 5% error margin. Additionally, if workers test the sample using light absorption methods, like turbidimetry and nephelometry, lipids can significantly affect the results. The higher the dilution rate, the less likely it will be affected when testing occurs using light absorption methods.
Paraproteins can interfere with lab results in several ways. Sometimes, the direct bilirubin results are higher than total bilirubin while at other times, high creatinine results do not correspond with a patient’s condition. When neither of these cases is present, then a lab result of high paraproteins should be considered suspicious. Often, a lab cannot reproduce the results using the same or a different sample. In order to prevent paraprotein interference, it is vital that the referral laboratories that you choose use equipment that has high ionic strength and add protein stabilizers or surfactants.
As a medical doctor, you want the very best for your patients. Therefore, you need to work with a referral laboratory prepared to minimize as much interference as possible. Contact us today to discuss our techniques and methods.