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Stepwise Success

It’s All About Technique

Published April 30, 2014 6:14 AM by Scott Warner

Running lab tests can look easy but often isn’t. Consider a common serology test, the heterophile screen. The OSOM Mono Test is one random example. The package insert lists the following with pictures:

  • For serum, plasma, or whole blood samples in tubes: Use the Transfer Pipette provided and add one drop to the Test Tube.
  • Slowly add 1 drop of Diluent to the bottom of the Test Tube.
  • Mix.
  • Remove the Test Stick(s) from the container. Re-cap the container immediately.
  • Place the Absorbent End of the Test Stick into the treated sample. Leave the Test Stick in the Test Tube.
  • Read results at 5 minutes. Positive results may be read as soon as the red Control Line appears.

This is pretty typical of these kinds of kits, maybe better than most. The pictures are a plus. But any lab tech can tell you the error is in the details. Much of the time the internal controls of the test can detect error in the addition of reagents, but they aren’t designed to monitor technique variation.

For example, I noticed many years ago in blood bank tube testing that latex gloves can carry a static charge that can attract serum drops if you aren’t careful. I learned to drop the sample while the tubes sat in the rack with the dropper at an angle, although this detail was not described in the procedure. I’ve no idea if this variable affects the OSOM kit, but an experienced tech might think of it.

Another example: depending on storage temperature, humidity, and time, dipsticks can show variation. Some urine dipstick vendors have recommended storing canisters on their sides to minimize bending. Perhaps, this isn’t significant with the OSOM kit and others like it, but this and other variables -- oil from bare fingertips, for example -- might affect test performance. Again something experience teaches.

Certainly this isn’t a criticism of any kit out there. It’s impractical for manufacturers to list every possible source of error. It’s all about technique.

NEXT: To Do or To Don’t

posted by Scott Warner


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About this Blog

    Scott Warner, MLT(ASCP)
    Occupation: Laboratory Manager
    Setting: Critical Access Hospital
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