Determinants and measures of quality in oral anticoagulation therapy

Abstract

Using clinical trial bleeding and thromboembolic complication rates to set quality measurement targets for anticoagulation clinics may not be appropriate, given the inherent difference in these patient populations. Additionally, there are pragmatic issues affecting the completeness and accuracy of adverse event gathering outside of a trial scenario that could be misleading. The time in the therapeutic range, however, is relatively easy to calculate and is a well substantiated surrogate marker for complication rates and should be a standard quality indicator. Benchmark targets for time in range are dependent on the methodology used in the calculation and should be adjusted accordingly.

Time in the Therapeutic Range (TTR): An Overly Simplified Conundrum

“…6,7 However, consider for a moment the following questions: 1) should one use the PTs measured in the first week or two before the warfarin effect is stabilized, recording information obtained before INR reached the target range when calculating the TTR; 2) what about INR results during planned temporary discontinuations of warfarin, such as during surgery, should these be included or excluded when calculating the TTR; and 3) how should one account for differences in the frequency of INR measurements? Ideally, the INR should be measured daily, but this is almost never the case.…”

“…With this approach, the number of INRs within the target range for all patients is divided by the total number of INRs completed with respect to all patients at the same point in time (such as at the midpoint of a date interval ± 7 days), using the last INR prior to the chosen date. 6,7 This provides a somewhat static picture, unless it is repeated over time to compute an average. This approach can be useful to estimate the TTR for a group of patients not being managed by a computerized anticoagulation database, though a limitation of this tactic is diminished accuracy due to the random variation of INR values.…”

“…Approximately 65% used the fraction of INRs in range, 15% relied upon the linear interpolation analysis and 10% employed the cross-section-of-the-files method. 6 In recent major clinical trials, the numbers have been higher, with mean and median values often in the midto high 60% range. [8][9][10][11] In the case of the four recent NOAC versus warfarin trials in AF, the respective mean and median TTR values were 62.2% and 66.6% in ARISTOTLE; 64.9% and 68.4% in ENGAGE AF; 55% and 58% in ROCKET AF; and a mean of 64% in RE-LY, with no median reported.…”

“…Additionally, I do not know of any direct outcome study showing that a particular method of calculating TTR is the best one, although when comparisons have been made within single sets of data, the TTR found by the Rosendaal method has generally been somewhat lower than that determined by the other two approaches. 6,7 Consequently, I believe that clinical trialists and the Food and Drug Administration need to consider these factors when assessing and comparing warfarin trials: namely, that some means of reporting these pertinent factors beyond just the TTR must become routine, and that clinicians need to understand them when extrapolating clinical trial results to their own practices. Finally, although I proposed above that TTRs be reported with additional information, this concept has not yet been applied to clinical practice, so there are no data to support that it is effectively superior in correlation with either efficacy or safety outcome results.…”

Impact of Point-of-Care Implementation in Pharmacist-Run Anticoagulation Clinics within a Community-Owned Health System: A Two-Year Retrospective Analysis

“…This method takes into account the number of visits that had INR results in range and Point-of-Care Testing in Pharmacist Anticoagulation Clinics divides this number by the total number of visits. 6 The primary outcome of this study was INR TTR. Secondary outcomes included major and minor bleeds, thromboembolic events, ER visits, hospitalizations, and cost.…”