From Jessica Warner, Kettering Health: Hi George, I was wondering whether there has ever been a discussion about evaluating these ranges and whether there’s a consensus on what they should be. I have been in my job for 12 years and never looked at them to change them until an AC at another health system asked me to. I had just adopted what we have been using. I started poking around online and learned that I might actually be a little high. My PTT is set at >128 seconds, and my INR is >6.0. So after poking around, now I’m curious if maybe I need to evaluate and update. Thanks!
A solicited response from Ali Sadeghi-Khomami, PhD, Director of Research & Development, Precision BioLogic Inc.
Hi George, thank you for sharing this question. Based on ICSH recommendations, there is no universally mandated critical INR or aPTT value, and laboratories should establish thresholds appropriate for their reagents, instruments, patient population, and clinical practice. For INR, ICSH recommends a critical threshold between 4.0 and 6.0, with many laboratories using ≥5.0. For aPTT, ICSH does not prescribe a specific cutoff and recommends that each institution determine its own value based on reagent sensitivity, heparin response, and stakeholder input. Jessica’s current thresholds (INR >6.0 and aPTT >128 seconds) are not unreasonable and fall within the ranges reported by many laboratories. However, since these limits have not been reviewed in many years, it may be worthwhile to benchmark against current practices, review historical critical results, and consult local clinicians to confirm that the selected values remain clinically actionable.
Useful references:
https://www.thieme-connect.com/products/ejournals/pdf/10.1055/s-0039-1697677.pdf
https://academic.oup.com/ajcp/article-abstract/136/6/836/1760468?redirectedFrom=fulltext&login=false
Overall, I would not suggest changing the thresholds based solely on published surveys. A local risk-based assessment involving the laboratory director and clinical stakeholders would be the most appropriate approach.
Best regards, Ali
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