Interference in ionized calcium measurements by heparin salts.

Author(s): Landt M, Hortin GL, Smith CH, McClellan A, Scott MG

Publication: Clin Chem, 1994, Vol. 40, Page 565-70

PubMed ID: 8149611 PubMed Review Paper? No

Purpose of Paper

Conclusion of Paper

Studies

1. Study Purpose

   The purpose of this study was to determine the effects of anticoagulant type and concentration on iCa, pH and gas levels in blood specimens. The effect of anticoagulant concentration was examined by partial filling of syringes and by using syringes with less anticoagulant.

   Summary of Findings:

   At all concentrations, Li heparin decreased iCa below levels found in control blood without anticoagulant. At low concentrations, Zn heparin increased iCa levels, but at higher concentrations, Zn heparin led to decreased iCa and pH. In contrast, EB heparin had no effect on iCa measurement. When 1.5 mL or less blood was collected in tubes containing CNLZ heparin with more than 78 g/ kg Zn, iCa concentrations were higher than in control blood. When CNLZ heparin tubes contained less than 59 g/kg Zn, iCa measurements decreased in specimens with a volume between 0.75 and 3 mL. However, iCa values were within 0.025 mmol/L of control when 0.75-3 mL specimens were collected in CNLZ heparin tubes with a Zn concentration between 59.4 and 78 g/kg. Collection of blood into tubes containing CNLZ heparin with a Zn concentration of 74.2 g/kg led to pH, oxygen, carbon dioxide and total calcium levels similar to control, but collection in tubes containing EB heparin led to an increase in measured total calcium, but no other significant effects. Although iCa differed between serum and CNLZ or EB plasma collected from cardiac patients, total calcium levels were similar in CNLZ plasma and serum, but were significantly lower (p<0.01) than in EB plasma.

   Biospecimens

   • Bodily Fluid - Blood

   Preservative Types

   • None (Fresh)

   Diagnoses:

   • Normal

   Platform:

   Analyte	Technology Platform
   Electrolyte/Metal	Clinical chemistry/auto analyzer
   Gas	Clinical chemistry/auto analyzer
   Small molecule	pH

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Biospecimen Acquisition	Anticoagulant	Calcium-neutralized zinc/lithium heparin Electrolyte balanced heparin Lithium heparin Zinc heparin None Multiple concentrations evaluated
   Biospecimen Aliquots and Components	Aliquot size/volume	0.4-3 mL

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