ITC ProTime Microcoagulation System User Manual
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Table 2 shows examples of how the calculation of PT seconds is affected by changing the ISI. As the ISI
increases, the plasma equivalent PT decreases at any given INR. For example, a patient with INR = 3.00
would have PT seconds = 39.2 if the ISI is the default ISI = 1.0 or PT seconds =21.3 if the ISI is reset to
ISI = 2.0.
Expected Values
ProTime measures both normal and therapeutic prothrombin times in fresh whole blood. Results are
displayed in plasma equivalent seconds and INR. Expected values for patients taking oral anticoagulants
depend on the patient’s disease state and the target values established by the physician.
Sample Condition
INR
PT Seconds (ISI = 1.0)
Normal
0.8-1.2
10.4-15.7 sec
Low anticoagulation
1.5-2.0 19.6-26.1
sec
Moderate anticoagulation
2.0-3.0
26.1-39.2 sec
High anticoagulation 2.5-4.0 32.6-52.2
sec
Note: The ProTime instrument converts whole blood clotting time to INR, then calculates PT
seconds. The default ISI used in this calculation is 1.0. Please see the For Professionals Only
– Program Mode section if you wish to select an ISI that is more closely aligned with the local
lab reagent.
The ProTime instrument has been tested extensively by doctors, nurses and patients. Eighty-four people,
ages 7 to 81, participated in the first home-use trial. The trial was conducted to see how well ProTime
results compare to the lab. Comparisons of this type are described by correlation values and a correlation
value near 1.0 means the comparison is good. The home tests compared to tests run at the clinic using
ProTime with venous samples (421 samples) had a correlation of 0.92. The home test results compared to
a reference laboratory results (368 samples) had a correlation of 0.87. These correlation values mean that
home testing is comparable to lab testing.
Precision
Precision testing was conducted with two levels of standard control plasma substrate preparations (Level I
and Level II).
A. Standard ProTime Cuvette
Control Precision
n
Mean
SD
Within day
17
0.9
0.06
Level I
Day-to-day (5 days)
4/day
1.0
0.08
Within day
19
3.2
0.19
Level II
Day-to-day (5 days)
4/day
3.2
0.12
B. ProTime3 Cuvette
Control Precision
n
mean
SD
Within day
18
0.9
0.07
Level I
Day-to-day (5 days)
4/day
0.9
0.12
Within day
20
4.0
0.19
Level II
Day-to-day (5 days)
4/day
4.2
0.22