Impact of short periods with worsened or improved INR control on life expectancy and QALYs in patients with atrial fibrillation

IntroductionWarfarin-treated patients with poor international normalized ratio (INR) control, measured with time in therapeutic range (TTR) or the standard deviation of transformed INR (SDTINR), have an increased risk for clinical events. To what extent only a short period with an altered INR control may influence outcomes remains unknown. This study assessed the impact of transient periods of worsened or improved INR control on life expectancy and quality-adjusted life years (QALYs) among warfarin-treated patients with atrial fibrillation (AF) using both metrics.Materials and methodsWarfarin-treated patients with AF, registered in the patient record system Journalia during years 1985-2000, were included. Information on all-cause mortality was collected from the Cause of Death Register. Hypothetical scenarios where patients were assumed to have a transiently altered INR control during 30 days were modeled statistically using hazard functions, and the impact on remaining life expectancy and QALYs was assessed.ResultsWhen using SDTINR, a 70-year old man within the 20th best INR control percentile was estimated to lose 7.4 days of life or 0.0100 QALYs from a 30-day long worsened INR control to that of an average 70-year old male patient. Correspondingly, 4.0 days of life or 0.0059 QALYs would be gained if a 70-year old man within the 20th worst INR control percentile would have an average INR control during 30 days. The magnitudes were smaller when TTR was used to determine INR control.ConclusionsEven short periods of an altered INR control is expected to have impact on life expectancy and QALYs among patients with AF.