According to Zengi (2023), majority of tests revealed no discernible difference between LIH and serum. Nonetheless, total error (TE) values for a few analytes were higher than the total permitted error (TEa) limitations obtained from the biological variation database. Notably, the insulin TE value was almost entirely consumed even though it did not surpass TEa. As a result, the investigation established the alternate permissible error levels for a few tests and discovered that, with the exception of lactate dehydrogenase (LDH), serum tubes could generally be substituted with plasma tubes for most assays. In the emergency laboratory, plasma tubes enhanced sample quality, eliminated aspiration errors, and shortened time to target. Significant TAT decreases have been seen after moving to plasma tubes. As a result of the study, serum tubes can be substituted with LIH tubes for the majority of clinical chemistry and immunoassay procedures. Clinical laboratories can decrease staff workloads and enhance the quality of care provided by utilizing LIH tubes.

Reference:

Zengi, O. (2023, September 28). The transition from gel separatory serum tubes to lithium heparin gel tubes in the clinical laboratory. Journal of Health Sciences and Medicine. https://dergipark.org.tr/en/pub/jhsm/issue/80018/1341282

Back in ancient days we used to use Serum gel separator tubes (SST or Tiger Top) or Red Top (non-gel) tubes for almost everything Chemistry, and using heparinized plasma was limited almost exclusively to coagulation or cellular testing. It took me many years to first see and then get used to using heparinized samples for Chemistry tests in clinical assays. However, one important factor in the acute care medical setting (i.e. hospitals, clinics, etc.) is TIME. Both tubes mentioned above are gel separator tubes which make processing much more convenient for those tests for which gel is not an issue. They handle automation much better (tubes can be tilted or inverted, and pose less risk of fibrin clots being sucked up into sensitive instruments); they increase sample viability (certain serum or plasma analyte levels start to change with time if not separated from the cells,); and they make things more "neat" (less mess in terms of accidental spills and easier to manually pour or decant serum or plasma sample without risk of cellular contamination coming along for the ride.)

However, the most significant difference between a Lithium Heparin gel tube versus the various Serum Separator gel tubes is ZERO CLOTTING TIME IS NEEDED. Processing time for samples in terms of throughput is always a matter for consideration in any laboratory. However, in an acute care setting such as a hospital with an emergency room, active OR or ICU, minutes can sometimes mean life or death.

For example, a potential cardiac patient comes into your Emergency Room. The newer Troponin assays are both more sensitive (ex. hsTNI) and run faster than the older ones. However often the greater delay can come in terms of waiting for a serum sample to clot. This applies even more so if the patient has a cardiac medical history and is already on anti-clotting medications such as Coumadin, Warfarin or the new antiplatelet types. In either case, a serum sample can take anywhere from an average "normal" 10 minutes up to 30-45 minutes to clot thoroughly. Then the sample needs to be centrifuged and assayed. What could have been a 30–35-minute turn-around time has now potentially become 45, 50 minutes or even broken the "golden hour" for STAT turn-around times (some hospitals have cardiac protocols demanding a 30–45-minute TAT for cardiac assays.)

Every wasted minute potentially means dead or dying cardiac tissue.

The same time-sensitivity can apply to many other critical STAT assays - anything from CHF (BNP, or ntBNP assays,) thrombosis/stroke protocols, (D-Dimer, CK,) to diabetics in DKA to ICU patients or Labor & Delivery protocols.

Every second wasted in a hospital laboratory can potentially effect negative outcomes.

With regards to the question by some of why it is Lithium Heparin instead of some others, and wouldn't the Heparin interfere with Lithium assays? Yes, it would - which is why you certainly wouldn't use a LiH test tube for a Lithium test specimen. However, the other commercially available alternative - Sodium Heparin (NaH) would interfere with a significantly greater number of samples as the majority of samples being tested in a hospital Chemistry department involve assays for patient Sodium levels.

And so LiH is the less interfering alternative and can be used for infinitely more diverse tests than just worrying about testing for Lithium. Additionally, and most Therapeutic Drug Monitoring (TDM) laboratory protocols prefer/require the use of a plain Red Top tube and not a gel tube in order to prevent potential interference with adsorbing drug levels.

And so at least from my experience TIME is the most beneficial factor with regards to using LiH Plasma gel tubes versus the various Serum gel tubes available today.

Lithium heparinized plasma (LIH) tubes can improve the sample quality, reduce aspiration errors, and decrease the turnaround time (TAT). In the study before switching to plasma, serum samples had 0.88% aspiration errors, but after switching to plasma, they had 0.44%. Aspiration errors are statistically significant, as they're one of the factors that can influence TAT. The median values from sample acceptance to device entry decreased from 21 to 17 minutes after switching to plasma samples, thus improving the TAT. These factors open up the possibility for improved quality healthcare and reduce the workload of hospital staff.