Other commercially available CRP controls:
Handle and use according to the instructions
for each control substance. Acceptable limits for the control must be defined with precision
results gained with the QuikRead go instrument. The blanking process might not succeed if
you use a control that contains artificial red blood cells.
9
Results’ interpretation
Elevation of CRP value is unspecific and the results should be interpreted in the light of
other clinical findings.
CRP test result
Interpretation of result
7
< 10 mg/L
Excludes many acute inflammatory diseases, but does not specifically
exclude inflammatory processes.
10–50 mg/L
Elevated concentrations found in acute disease that occur in the presence
of a slight to moderate inflammatory process.
> 50 mg/L
Indicates high and extensive inflammatory activity.
10 Limitations of the procedure
Assay procedures other than those specified in these instructions may yield questionable
results. Some substances may interfere with the test results; please see Section 12.
“Performance Characteristics”.
Test results should never be used alone, without a complete clinical evaluation, when making
a diagnosis. Intra-individual variations in CRP are significant and should be taken into account
– for example, by means of serial measurements – when interpreting the values.
11 Expected values
The assay reference range limit was determined by using 143 apparently healthy adults
(59 males and 84 females) with age 19–65 according to CLSI EP28-A3C guideline. Based
on the results the 95% reference limit was concluded to be ≤ 5 mg/L for each sample type.
Results are based on a non parametric approach.
However, each laboratory is recommended to establish a range of normal values for their
population in their region.
12 Performance characteristics
Method comparison
Patient plasma samples were measured using two clinical laboratory methods, and the
QuikRead go CRP method. Summary of correlation studies is presented in the table below.
Passing-Bablok analysis
Clinical laboratory method 1
Clinical laboratory method 2
y
r
n
=
=
=
1.00x + 1.0
0.994
116
y
r
n
=
=
=
0.93x + 1.4
0.987
113
Whole blood versus plasma comparability
In a comparison of 104 patient samples, whole blood (y) and plasma (x) were found
comparable. y = 1.03x – 0.3
Precision
A precision study was performed according to Clinical and Laboratory Standards Institute
(CLSI) guideline EP5-A2.
Within-run, between-day and total precision
Sample
material
Sample
number
Number
of days
Mean CRP
(mg/L)
Within-run
CV (%)
Between-day
CV (%)
Total
CV (%)
Whole blood
Sample 1
Sample 2
Sample 3
20
20
20
9
52
177
4.5
1.4
1.9
4.3
2.4
2.8
6.2
3.2
3.6
Plasma
Sample 1
Sample 2
Sample 3
20
20
20
10
55
148
3.7
1.5
2.0
0.1
0.4
1.0
4.2
1.9
2.4
Control
Sample 1
20
30
2.0
3.1
3.7
Measuring range
For whole blood samples the measuring range is 5–200 mg/l at the normal hematocrit level
of 40%. If the hematocrit is lower or higher than 40%, the measuring range will change
according to the table below. Starting from QuikRead go instrument software version 3.1,
the instrument displays a CRP result at hematocrit range of 15–75%. Previous instrument
software versions display CRP results at hematocrit range of 20–60%. The CRP result is not
displayed, if the level of hematocrit is outside the range of 15–75% or 20–60% (depending
on the instrument software version).
Sample type Hematocrit % Sample volume Measuring range mg/l CRP
In cases when
the result is
above or below
the measuring
range, the
result will be
displayed,
for example
“> 200 mg/l
CRP”.
Whole blood
sample
15–19
20–28
29–35
36–41
42–46
47–50
51–53
54–56
57–60
61–62
63–64
65–66
67–68
69–70
71–72
73–74
75
20 µl
5–150
5–160
5–180
5–200
5–220
5–240
5–260
5–280
5–300
5–330
5–340
5–360
5–390
5–410
5–440
5–470
5–510
Plasma/
Serum sample
–
20 µl
12 µl
5–120
5–200
Interference
Interferent
No interference found up to concentration
Bilirubin
Vitamin C
Triglycerides
Cholesterol
Rheumatoid factors (RF)
Leucocytes
Anticoagulants (Li-heparin or EDTA)
400 µmol/l
200 µmol/l
11.5 mmol/l
9.0 mmol/l
525 IU/ml
145x10
9
cells
No interference
Most heterophilic or anti-sheep antibodies in the samples do not interfere with the test, as
the assay antibodies lack the Fc-part. In rare cases, interference by IgM myeloma protein
has been observed.
