Key result
The Point-of-Care i-STAT method showed close correlation with laboratory Stago for 5 years (bias 0.23 INR units), but developed a transiently increased bias of 0.73 INR units in year 6.
Why the study?
Does the Point-of-Care i-STAT method maintain long-term correlation with the laboratory Stago method for determining INR?
Observational
Yes
Does the Point-of-Care i-STAT method maintain long-term correlation with the laboratory Stago method for determining INR?
Point-of-care INR devices can experience significant assay drift over time, highlighting the need for continual correlation with laboratory methods.
Answers are grounded in this paper and cite their sources.
POC INR devices warrant ongoing lab correlation to detect drift; leaves open generalizability of transient bias beyond this device.
OBJECTIVES: To perform long-term comparison between laboratory Stago and Point-of-Care (POC) i-STAT methods for determining the international normalized ratio (INR). METHODS: This was a multicenter method comparison of patient INR results and factors related to performance variance. RESULTS: For 5 years, the assays demonstrated close patient correlation within and above the 3.5 INR therapeutic range cutoff (bias, 0.23 INR units). Patient results above 3.5 INR were bimodal, with 60% demonstrating an i-STAT INR bias of less than 0.5. Several patient conditions were associated with the presence of a higher i-STAT bias. In year 6, a broader range i-STAT bias developed, increasing to 0.73 INR units. The increased bias persisted for 3 years, then returned to initial levels following i-STAT adjustments. The substantial increase in i-STAT bias after a long period of stability was partly corrected by renewed correlation to the international reference preparation. Additional assay drift is discussed in relation to thromboplastin reagents and other testing variables. CONCLUSIONS: This study emphasizes the need for continual laboratory correlation with POC devices and caution in using published comparisons.
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Sephel et al. (2013) reported an observational. Point-of-Care (POC) i-STAT method vs. Laboratory Stago method was evaluated on INR bias between methods. The Point-of-Care i-STAT method showed close correlation with laboratory Stago for 5 years (bias 0.23 INR units), but developed a transiently increased bias of 0.73 INR units in year 6.
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