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But when this type of sample is run on the Mythic22, the reagent cannot convert all the methemoglobin back
to oxyhemoglobin.
As a result, control blood hemoglobin is only partially converted and the resulting measurement is performed
on a mix between oxy- and methemoglobin, leading to a false, underestimated value, for methemoglobin is
counted for only about half of its real concentration. The higher methemoglobin concentration, the bigger
difference between expected and measured value.
Thus when standard controls are run fresh, retrieved hemoglobin value is very close to anticipated target on
methemoglobin technique instruments. But while tubes are aging, multi-sampled etc, hemoglobin turns into
methemoglobin and results become under evaluated.
That’s the reason why specific controls and calibrators were designed to match the Mythic22
technique.
In those samples cells were fixed with different molecules and hemoglobin is stabilized in order to prevent
oxidation into methemoglobin during lifespan of the control. Therefore, when run, these controls return an
accurate value of hemoglobin.
And the exact reserve situation is observed when Mythic22 specific controls are run onto a methemoglobin
measuring instrument: since hemoglobin is stabilized to prevent methemoglobin formation, methemoglobin
forming reagents cannot convert hemoglobin accurately, resulting in too high a value (for absorbance
extinction of oxyhemoglobin is much higher than the one of methemoglobin).
When the instrument is properly calibrated with the right calibrator, there is virtually no bias on hemoglobin
measurement on human samples, as compared to other technique instruments.
As explained, the reagent and the instrument were designed to promote oxyhemoglobin on human (or animal)
sample and actually perform accurate measurements.
4 Recommendations:
Prior to running a national survey sample, local distributors should interact with government agencies to
either have a specific control prepared for the Mythic22 line instruments or more likely to have values
established for surveys samples on the Mythic22 instruments. Therefore a coefficient factor could be
implemented to restore accuracy on such samples, without tweaking human sample calibration.
Hence, since composition of surveys’ samples is likely to vary between countries, it is impossible to set a
general coefficient and the evaluation should be performed in each country.
8.2 LEUCOCYTE ANALYSIS
The leukocyte number analysis is done by impedance in the WBC counting chamber, the other ten parameters
are obtained by flow cytometry measurement (see section 8.1.2).
All the thresholds of the differential are adjustable in the 20 blood types (see section 3.4.4.2).
Pathologies (adjustment section 3.4.4.1)
Leucocytosis : WBC>WBC h
Leucopenia : WBC<WBC b
Lymphocytes in percentage
Lymphocytosis : LYM>LYM h (% &/or #)
Lymphopenia : LYM<LYM b (%&/or #)
Monocytosis : MON>MON h (%&/or #)
Neutrophils in percentage
Neutrophilis : NEU > NEU h (%&/or #)
Neutropenia : NEU < NEU b (%&/or #)
Eosinophils in percentage
Eosinophilis : EOS > EOS h (%&/or #)
Basophilis : BAS > BAS h (%&/or #)
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