Leukocytosis interference in clinical chemistry: Shall we still interpret test results without hematological data?

The stability of blood gases and CO-oximetry under slushed ice and room temperature conditions

OBJECTIVES

Human blood gas stability data is limited to small sample sizes and questionable statistical techniques. We sought to determine the stability of blood gases under room temperature and slushed iced conditions in patients using survival analyses.

METHODS

Whole blood samples from ∼200 patients were stored in plastic syringes and kept at room temperature (22-24 °C) or in slushed ice (0.1-0.2 °C) before analysis. Arterial and venous pO2 (15-150 mmHg), pCO2 (16-72 mmHg), pH (6.73-7.52), and the CO-oximetry panel [total hemoglobin (5.4-19.3 g/dL), percentages of oxyhemoglobin (O2Hb%, 20-99%), carboxyhemoglobin (COHb, 0.1-5.4%) and methemoglobin (MetHb, 0.2-4.6%)], were measured over 5-time points. The Royal College of Pathologists of Australasia's (RCPA's) criteria determined analyte instability. Survival analyses identified storage times at which 5% of the samples for various analytes became unstable.

RESULTS

COHb and MetHb were stable up to 3 h in slushed ice and at room temperature; pCO2, pH was stable at room temperature for about 60 min and 3 h in slushed ice. Slushed ice shortened the storage time before pO2 became unstable (from 40 to 20 min), and the instability increased when baseline pO2 was ≥60 mmHg. The storage time for pO2, pCO2, pH, and CO-oximetry, when measured together, were limited by the pO2.

CONCLUSIONS

When assessing pO2 in plastic syringes, samples kept in slushed ice harm their stability. For simplicity's sake, the data support storage times for blood gas and CO-oximetry panels of up to 40 min at room temperature if following RCPA guidelines.

Stability of hematological analytes during 48 hours storage at three temperatures using Cell-Dyn hematology analyzer

Background

The complete blood count (CBC) with differential leukocyte count (DLC) is one of the most common tests requested by physicians. The results of this test are affected by storage temperature and time of incubation. This study was designed to evaluate the stability of hematologic parameters in blood specimens stored for 48 h at three temperatures.

Methods

K2-EDTA - blood was collected from 22 healthy adults. The CBC was performed using a hematology analyser immediately; 0 time point and at 4, 8, 12, 16, 20, 24, and 48 h after storage at 4 °C, 10 °C or 23 °C. Changes in values of CBC parameters from the 0 time point were determined and reported as % of the initial value.

Results

Red blood cells, platelet, hemoglobin, and mean corpuscular hemoglobin were found stable during 48 h storage at 4 °C, 10 °C or 23 °C. Hematocrite and mean corpuscular volume increased, while white blood cells decreased at 48 h when stored at 23 °C. Lymphocytes, neutrophils, eosinophils, and basophils showed significant differences after 12 h of storage at 23 °C.

Conclusions

Red blood cells, platelet, hemoglobin, and mean corpuscular hemoglobin are the only suitable parameters without refrigeration during 24 h storage. When CBC and DLC are performed, 4 °C can be recommended as the most suitable storage temperature for 12 h storage.