Objective
Point-of-care (POC) testing allows rapid assessment of hemoglobin (Hgb) and hematocrit
(Hct) values. This study compared 3 POC testing devices—the Radical-7 pulse oximeter
(Radical-7, Neuchȃtel, Switzerland), the i-STAT (Abbott Point of Care, Princeton, NJ), and the GEM 4000
(Instrumentation Laboratory, Bedford, MA)—to the hospital reference device, the UniCel
DxH 800 (Beckman Coulter, Brea, CA) in cardiac surgery patients.
Design
Prospective study.
Setting
Tertiary care cardiovascular center.
Participants
Twenty-four consecutive elective adult cardiac surgery patients.
Interventions
Hgb and Hct values were measured using 3 POC devices (the Radical-7, i-STAT, and GEM
4000) and a reference laboratory device (UniCel DxH 800). Data were collected simultaneously
before surgery, after heparin administration, after heparin reversal with protamine,
and after sternal closure. Data were analyzed using bias analyses. POC testing data
were compared with that of the reference laboratory device.
Measurements and Main Results
Hgb levels ranged from 6.8 to 15.1 g/dL, and Hct levels ranged from 20.1% to 43.8%.
The overall mean bias was lowest with the i-STAT (Hct, 0.22%; Hgb 0.05 g/dL) compared
with the GEM 4000 (Hct, 2.15%; Hgb, 0.63 g/dL) and the Radical-7 (Hgb 1.16 g/dL).
The range of data for the i-STAT and Radical-7 was larger than that with the GEM 4000,
and the pattern or slopes changed significantly with the i-STAT and Radical-7, whereas
that of the GEM 4000 remained relatively stable. The GEM 4000 demonstrated a consistent
overestimation of laboratory data, which tended to improve after bypass and at lower
Hct/Hgb levels. The i-STAT bias changed from overestimation to underestimation, the
latter in the post-cardiopulmonary bypass period and at lower Hct/Hgb levels. By contrast,
the Radical-7 biases increased during the surgical procedure and in the lower ranges
of Hgb.
Conclusion
Important clinical differences and limitations were found among the 3 POC testing
devices that should caution clinicians from relying on these data as sole determinants
of when or when not to perform transfusion in patients. Even though a low bias might
support the use of POC data, further analysis of the bias plots demonstrates pattern
changes during the surgical procedure and across the range of Hct/Hgb data.
Key Words
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