Is Sample Quality in the Eye of the Beholder?

Here’s a simple experiment to try in your lab: Find a hemolysed sample and separately ask five different medical laboratory scientists to judge the amount of hemolysis present. What you’ll probably find is that “grossly hemolyzed” is most definitely in the eye of the beholder.

Along with hemolysis, lipemia and icterus are determined by judgment calls made by laboratory scientists. Considering that these three interferences make up the bulk of interferences found in patient samples, “eye of the beholder” may not be good enough. Luckily, with most modern chemistry analyzers, it does not have to be.

Most major chemistry analyzers now perform what we like to call “indices”. The HIL (hemolysis, icterus, lipemia) indices are directly measured by the instrument for a given sample. If any of these three interfering substances are present, the instrument will determine both its presence and its concentration. This last point is important also, because some analytes are only affected by a significantly large amount of the interfering substance. Being able to directly measure these interfering substances, allows the instrument to be set to deal with the affected sample in the most appropriate way. It can be set to not analyze those tests affected, or to not report the results on affected tests, or to simply flag the result for footnoting. Computer systems across the interface can likewise be automatically programmed to accept the HIL numbers and respond appropriately.

Analyzers measure the HIL indices in different ways and until recent years, pediatric labs have often been unable to take advantage of analyzer-measured indices. In pediatrics, especially in infant patients, sample volume is often an issue, and so this feature has traditionally been turned off in pediatric labs. However, there are instruments on the market that measure the indices through the pipet tip without using up any sample volume including most of the Ortho Diagnostics analyzers, like the Fusion 5,1 and the 5600. This feature is one of the reasons these instruments are so often found in pediatric labs. In addition, those instruments that use sample volume are now capable of using microliter quantities, like the Siemens Vista or the Roche Cobas 6000.  Utilizing minimal sample volume for this measurement allows the HIL features to be used on these instruments in almost all situations.

Thus the good news is that the sample quality and appropriateness for any given test no longer needs to be in the eye of the beholder.

-Patti Jones

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