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Related Experiment Videos

Identifying delayed separation in plasma homocysteine specimens.

M Chen1, K L Nuttall

  • 1Department of Pathology, University of Utah School of Medicine, Salt Lake City 84132, USA.

Annals of Clinical and Laboratory Science
|October 21, 1999
PubMed
Summary

Delayed blood sample separation can falsely elevate homocysteine levels. This preanalytic issue, indicated by the arginine/(arginine + ornithine) ratio, was significantly more common in elevated homocysteine results.

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Area of Science:

  • Clinical Chemistry
  • Biochemistry
  • Laboratory Medicine

Background:

  • Delayed plasma separation from blood cells is a known cause of inaccurate homocysteine measurements.
  • Preanalytic variables significantly impact laboratory test results, affecting patient diagnosis and treatment.

Purpose of the Study:

  • To investigate the incidence of delayed plasma separation in patient blood samples.
  • To determine if delayed separation is associated with falsely elevated homocysteine levels.

Main Methods:

  • Examined patient specimens using the arginine to the sum of arginine plus ornithine [arg/(arg + orn)] ratio.
  • Defined a ratio <0.50 as indicative of delayed plasma separation.
  • Compared the incidence of delayed separation in samples with low homocysteine (<10 micromol/L) versus elevated homocysteine (>18 micromol/L).

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Main Results:

  • Specimens with elevated homocysteine showed a significantly higher frequency of delayed separation (11/12, p = 0.009) compared to those with low homocysteine (6/10).
  • The average arg/(arg + orn) ratio was lower in the elevated homocysteine group (0.31) than in the low homocysteine group (0.47).
  • Delayed separation was a frequent occurrence, particularly in samples with elevated homocysteine.

Conclusions:

  • Delayed plasma separation is a common preanalytic problem.
  • This preanalytic issue likely contributes to falsely elevated homocysteine results in a significant number of patients.
  • Routine monitoring of preanalytic variables like sample separation time is crucial for accurate homocysteine testing.