In another thread, discussion moved to the question of testing frequency based on previous INRs.
The idea was that if a person has a 'stable' INR over a particular period, that this person is 'stable' and doesn't need as frequent testing. The issue of what 'stable' meant came up -- and it was clear that my basic definition didn't match those of some others on the forum.
To me, thinking as an almost-statistician, stable meant that the same value came up repeatedly. Thus, an INR of 2.2 on January 1 and of 2.6 on February 1 were NOT stable. Others seem to define 'stable' as meaning 'in range.' If this was the case, the previously mentioned tests would show a 'stable' INR.
As far as INR management is concerned, I'm not entirely convinced which definition is the most important. Certainly, being in range from test to test is crucial. It would be very comforting to believe that because earlier testing showed that you were in range each time you tested, that the time between tests can be extended.
Unfortunately, this isn't always the case. As others have noted, many things can move an INR out of range -- dietary changes, activity changes, change in medications, starting or stopping certain antibiotics, or some undetermined events. It's not always possible to predict what may make our INRs go a bit higher or lower than we expect.
Less frequent testing because previous tests showed that a person has been consistently in range when that person was tested still doesn't account for the times between tests when it's possible that an INR actually moved out of range, only to come back into range when the next test was done. 'Stability' doesn't account for possible risky periods between tests.
With the simplicity and relative low cost of testing with the small meters (home or clinic testing that doesn't require a venous blood draw), there's little reason not to test weekly or, at most, bi-weekly. BUT - if this really is an issue, perhaps a protocol that allows time between tests to be extended when a person's INR is near the middle of the range, but tests more frequently when the person's INR is at or near the high or low end of the range would be appropriate.
Personally, as long as I have a supply of strips, I'll test weekly or stretch these intervals out a bit to preserve my supply of strips. I don't make significant dosage changes unless my INR is way out of range (like, for example, the 1.2 I had recently, or a high 4 that I also experienced). I check diet and other factors or changes that may have accounted for the move out of range, then perhaps do dosage adjustments in both cases.
Although the idea of 'stable' may have changed in my mind, I still think that testing weekly is not overkill and is appropriate even for people with 'stable' INRs, diets, dosages and activities.
What do YOU think?
The idea was that if a person has a 'stable' INR over a particular period, that this person is 'stable' and doesn't need as frequent testing. The issue of what 'stable' meant came up -- and it was clear that my basic definition didn't match those of some others on the forum.
To me, thinking as an almost-statistician, stable meant that the same value came up repeatedly. Thus, an INR of 2.2 on January 1 and of 2.6 on February 1 were NOT stable. Others seem to define 'stable' as meaning 'in range.' If this was the case, the previously mentioned tests would show a 'stable' INR.
As far as INR management is concerned, I'm not entirely convinced which definition is the most important. Certainly, being in range from test to test is crucial. It would be very comforting to believe that because earlier testing showed that you were in range each time you tested, that the time between tests can be extended.
Unfortunately, this isn't always the case. As others have noted, many things can move an INR out of range -- dietary changes, activity changes, change in medications, starting or stopping certain antibiotics, or some undetermined events. It's not always possible to predict what may make our INRs go a bit higher or lower than we expect.
Less frequent testing because previous tests showed that a person has been consistently in range when that person was tested still doesn't account for the times between tests when it's possible that an INR actually moved out of range, only to come back into range when the next test was done. 'Stability' doesn't account for possible risky periods between tests.
With the simplicity and relative low cost of testing with the small meters (home or clinic testing that doesn't require a venous blood draw), there's little reason not to test weekly or, at most, bi-weekly. BUT - if this really is an issue, perhaps a protocol that allows time between tests to be extended when a person's INR is near the middle of the range, but tests more frequently when the person's INR is at or near the high or low end of the range would be appropriate.
Personally, as long as I have a supply of strips, I'll test weekly or stretch these intervals out a bit to preserve my supply of strips. I don't make significant dosage changes unless my INR is way out of range (like, for example, the 1.2 I had recently, or a high 4 that I also experienced). I check diet and other factors or changes that may have accounted for the move out of range, then perhaps do dosage adjustments in both cases.
Although the idea of 'stable' may have changed in my mind, I still think that testing weekly is not overkill and is appropriate even for people with 'stable' INRs, diets, dosages and activities.
What do YOU think?
