Stability of carboxy-hemoglobin during storage at different temperatures.

Abstract

Accurate determination of carboxy-hemoglobin (COHb%) is essential for the assessment of hemoglobin mass (Hbmass) by CO-rebreathing. To analyze blood samples for a certain period of time after blood collection, it is necessary to know the stability of the COHb% during storage. The aim of the study was to determine the stability of COHb% at different storage temperatures over a period of up to 3months. Twenty-five milliliters of cubital venous blood was taken from five volunteers (three females and two males) before and after inhalation of 0.8/1.0mL/kg carbon monoxide and stored at +20°C and +4°C for 6days and at -70°C for 12 weeks. Within the first 6days, the blood was analyzed daily, then weekly for 12 weeks. Additionally, Hbmass was determined in 13 endurance athletes immediately after blood collection and after storage for 3days (eight cyclists) and 7days (five swimmers) at +20°C or +4°C. COHb% before and after CO inhalation was 1.56 ± 0.48 and 5.86 ± 1.12%, respectively, and remained unchanged over 6days, with no difference between storage at different temperatures. The standard deviation (STD) over time was between 0.07% and 0.12%. Similarly, storage at -70°C for 12 weeks did not change COHb%, whereas STD was 0.07%. Hbmass determined immediately and, after 3 or 7days of storage, differed by 10 ± 7 g and 15 ± 11 g corresponding to a typical error of 0.8% and 1.1%. Blood storage at +20°C and +4°C for 6days and at -70°C for 12 weeks does not affect COHb% and has, therefore, no influence on Hbmass assessment.