Medica EasyStat - Page 39

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o p e r a t i n g t h e a n a l y z e r
r
As with all clinical instrumentation, the performance of the EasyStat analyzer
must be monitored using quality control samples. Each laboratory should estab-
lish their own quality control program. Medica requires the use of quality con-
trols every day patient samples are analyzed and after any troubleshooting.
Medica controls are designed to contain pH, PCO
2
, PO
2
, Na
+
, K
+
, Ca
++
,
and Cl
-
values that are within the typical patient population. Each lot of
EasyStat control contains an insert sheet indicating the expected ranges for
pH, PCO
2
, PO
2
, Na
+
, K
+
, Ca
++
, and Cl
-
. Using the 3 levels of controls as
part of the laboratory quality control program will aid in verifying analyzer
performance. If controls have results outside the expected ranges, the perfor-
mance of the analyzer may not be optimum. If necessary, corrective action
should be taken before reporting patient results. Factors that can shift control
results from the insert sheet ranges are:
l
control material temperature when ampule is opened (PO
2
control
values increase by 1.3% for every 1°C decrease in storage tempera-
ture from 23°C or PO
2
control values decrease by 1.3% for every
1°C increase in storage temperature from 23°C)
l
elevation (PO
2
control values decrease by 1% for every 1000 feet
(305m) above sea level)
l
correlation factors applied to quality control samples
The hematocrit controls are assayed quality control materials used to monitor
the measurements of hematocrit in the EasyStat analyzer. Electrical conductiv-
ity methodologies are used to determine hematocrit.
Medica hematocrit controls are designed to contain hematocrit values that are
within the typical patient population. Each lot of control contains an insert sheet
indicating the expected ranges for hematocrit. The values for each control ana-
lyte are based on multiple determinations performed on randomly selected sam-
ples from each lot. The expected range and mean values shown are provided as
a guide in evaluating analyzer performance. The mean value established should
fall within the expected value range shown on the chart provided.
As part of a good quality control program, each laboratory should establish
their own ranges for each lot of controls over multiple days. The ranges must
be examined for clinical significance.
Once established, enter the limits into the EasyStat analyzer under SET
REFERENCE LIMITS in the SETUP MENU.
The EasyStat stores quality control results for 3 levels (a maximum of 93 for
each level) when control samples are analyzed through ANALYZE QC.
The results for pH, PCO
2
, PO
2
, Hct, Na
+
, K
+
, Ca
++
, and Cl
-
are compared
to the quality control reference limits previously entered for the chosen level
of quality control. Levey-Jennings charts can be printed to document the per-
formance of the stored quality control sample results over time.