The Essence: The Best of April 2019

By Anne-Margaret Olsson posted 21 days ago

The Artery continues to be a great member benefit where you can receive solutions to your most perplexing questions.  This past month several solutions were shared including "How do labs reduce pre-analytical hemolysis?". Read on for our editor's picks of the best discussions on the Artery in April.

PTH Sample to Use: EDTA Plasma or Serum?
Initiated by Carmelo Moreno

Most labs use EDTA plasma, with one lab taking a separate sample of serum or heparin plasma for calcium determination. Plasma was traditionally thought to be best because specimens could be centrifuged immediately, which presumably inhibited protease action. One lab uses serum, however, and apparently several studies now show that PTH is stable for at least 24 hours whether collected in plasma or serum, with or without protease inhibitors.

Exudative Pleural Fluid pH Measurement
Initiated by Tony Wicheanvonagoon

How do labs determine pleural fluid pH—do any labs use pH meters? Respondents say that they actually use blood gas analyzers and that pH meters aren’t precise enough for this measurement. As one respondent explains, the pH of an aqueous solution is a function of temperature, and blood gas machines measure pH at 37°C while a pH meter measures pH at room temperature, making pH meter results higher and less accurate.

HbA1c Mainline Chemistry or HPLC
Initiated by Martin Abrams

What do other labs think of running HbA1c using a non-HPLC method? The general consensus is that, whether labs use HPLC, immunoassay-based automated analyzers, or another method, all HbA1c methods have limitations regarding hemoglobin variants. Therefore, when selecting a method, labs should consider the prevalence of hemoglobinopathies, in addition to lipemia interference, cost and time savings associated with adding to an existing high-throughput workflow, and the possible use of a disclaimer regarding the limitations of whichever method is used.

Decreasing Pre-Analytical Hemolysis?
Initiated by Charles Beavers

How do labs reduce pre-analytical hemolysis? An issue this pervasive requires a multi-pronged approach, and respondents recommended numerous strategies. These ranged from smaller changes such as discontinuing IV blood draws and using a discard tube first in the order of draw, to larger changes such as ensuring lab staff adhere to the institution’s specimen rejection and recollection policy, making the business case for 24/7 phlebotomy staff, and/or providing training on proper phlebotomy technique.