10 PERFORMANCE CHARACTERISTICS
Cholestech GDX Analyzer User Manual
11PERFORMANCE CHARACTERISTICS
Cholestech GDX Analyzer User Manual
Performance Characteristics
Clinical Trial Results
Clinical studies were carried out to assess the performance of the
Cholestech GDX System for the measurement of A1C in diabetic
patients. The results were compared with those for a number of
laboratory-based systems.
The equations for the GDX test compared to the Menarini Biomen
HA8140 and the Bayer DCA 2000 are as follows:
GDX = 0.9167 X DCA 2000 - 0.1323
GDX = 0.8968 X Menarini HA8140 + 0.7074
Precision
In comparative studies using three different batches of Cholestech GDX
Test Cartridges, the overall standard deviation was 0.23 (4.1% CV)
for a sample having a level of 5.7% A1C and 0.36 (3.8% CV) for a
sample having a level of 9.4% A1C.
Linearity and Temperature Effects
The Cholestech GDX System has been shown to give a linear
response from 4-15% A1C using patient samples. Values above
15% A1C are outside the validated range. Caution should be
exercised if results outside the validated range of 4-15% are
obtained. Cholestech GDX test results were shown not to be
affected by operating temperatures of 17-30°C (63-86°F).
System
Variant II HPLC
Mono S HPLC
Biomen 8121 HPLC
Total GHb Test
Glycomat 765 HPLC
Glycotest II
DCA 2000
Manufacturer
Bio-Rad
Pharmacia
Menarini
Sigma
Corning
Pierce
Bayer
Patient Number (n)
62
62
24
94
95
95
56
Correlation
r=0.98
r=0.98
r=0.97
r=0.96
r=0.94
r=0.97
r=0.96
Abnormal Hemoglobins
The Cholestech GDX assay uses boronate affinity chromatography
to determine the level of A1C in a blood sample. The presence of
hemoglobin variants in a sample, such as HbS, HbC and HbD,
which are known to affect other, non-boronate-based methods of
A1C measurement, do not interfere with the Cholestech GDX test.
In addition, the presence of fetal hemoglobin (HbF) in a sample
does not interfere with the Cholestech GDX test result.
5
Uremic
patients with high levels of carbamylated hemoglobin can also be
tested with the Cholestech GDX System.
Hemoglobin and Hematocrit
The Cholestech GDX System performs acceptably over a hemoglobin
a range of 8–20 g/dL and a hematocrit range of 30–60%.
Interfering Substance
The following substances were shown to have no effect on the
Cholestech GDX test result at the levels indicated: bilirubin 145
µmol/L, acetylsalicylic acid 300 µg/mL, caffeine 300 µg/mL,
acetoaminophenol 300 µg/mL and hydroxyzine dihydrochloride
300 µg/mL. Triglycerides at 8.6 mmol/L showed no effect on the
Cholestech GDX test result; however, elevated lipid concentrations
may interfere and cause low results in this type of assay.
Venous Sample Use/Storage
Venous samples may be stored at 2–8°C (36–46°F) for up to 4 days.
Store samples as whole blood, not as hemolysates or packed red
blood cells. Venous samples may use anticoagulants potassium-EDTA,
sodium citrate, sodium heparin, lithium heparin and fluoride.
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