Preanalytical errors in ionized calcium measurements induced by the use of liquid heparin.
The use of heparin in a liquid form to measure ionized calcium (Ca++) in plasma or whole blood can induce preanalytical errors by dilution and by changing the original Ca++ value by binding or by re-equilibration with calcium in the anticoagulant solution. To quantify these errors, Ca++ was measured on serum pools under different sampling conditions. Incomplete syringe filling and specimen volume/syringe nominal volume ratio effects were tested. Syringes were rinsed with saline to yield pure dilution effects, with sodium heparinate to study binding and with calcium-titrated heparinate to evaluate 'calcium-distortion'. Detailed tables provide percentage error values for all sampling conditions. Dilution errors could reach -5% and binding was always important (-14 to -50%). Distortion was minimal around 1.25 mmol/L but could reach -4% for high and +8% for low Ca++ values. Errors increased when syringes were not filled to their nominal volume, especially with small-sized specimens.
Sachs
C
C
Department of Physiology, University of Paris V, Necker-Enfants Malades Medical School, France.
Rabouine
P
P
Chaneac
M
M
Kindermans
C
C
Dechaux
M
M
Falch-Christiansen
T
T
D000925:Anticoagulants; D002118:Calcium / Q000097:blood*; D003951:Diagnostic Errors; D006493:Heparin; D006801:Humans; D012996:Solutions; D013048:Specimen Handling; D013594:Syringes
D000925:Anticoagulants; D012996:Solutions; D006493:Heparin; D002118:Calcium