Causes of a Discrepancy Between a Hemoglobin or Hematocrit Value Determined on a Conductivity-Based Point-of-Care Instrument (iStat, Other) and Other Hematology Analyzers
There may be a discrepancy between values for hemoglobin and hematocrit determined on a conductivity-based point-of-care (POC) device and other analyzers. This usually is small but sometimes can be significant.
Example of a conductivity-based POC device: iStat
The hematocrit is determined from the sample conductivity after correction for electrolyte concentrations. The hemoglobin value is the calculated from the hematocrit.
Most hematology analyzers use an optical method. A POC device using an optical method does not show the discrepancy seen with a conductivity-based POC device.
The discrepancy in hemoglobin readings may be 2 g/dL or more.
Causes of a low POC reading:
(1) low serum protein
(2) abnormal sodium
Causes of a high POC reading:
(1) elevated serum protein
(2) hyperlipidemia
(3) abnormal sodium
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