A Proposed Change to CLIA
A few years ago a local patient with a critical INR in our laboratory had his test repeated at a medical center in a nearby city with wildly different results. The patient telephoned us and complained. “I don’t know who is running your tests,” he said, “but they need to get their act together! I can’t drive an hour every time I need a blood test.”
The INR (International Normalized Ratio) is an exponential function:
( PT Patient / PT Normal )ISI
The ISI, or International Sensitivity Index, is a reagent constant that “normalizes” the ratio within a therapeutic range. But there is no such guarantee with critical values, a pitfall when reagent ISI values vary. While this detail doesn’t matter to physicians, it can be confusing to patients.
If, for argument sake, our method had a normal of 11 seconds, a reagent ISI of 1.6, and a patient result of 90 seconds, the INR is 28.8. If the big city lab uses 11 seconds, an ISI of 1.02, and gets 120 seconds for the patient, their INR is 11.4.
Which is correct? Convincing an angry patient that these are essentially the same result can be difficult.
A proposed CLIA amendment announced Monday will require laboratories to give results directly to patients “manually or electronically.” The amendment is intended to remove barriers and provide consistency in how patients request copies of their test results. I guess, that doesn’t sound like a terrible thing, since patients are entitled to their information.
But laboratory reports are often cryptic, abbreviated, and created for physician expedience. They typically do not convey subtle method variance such as ISI, issues which can be explained to physicians if a question of interpretation arises. Our reports are generally not designed for patient consumption, something laboratories may want to consider.
In the meantime, get ready for a lot more telephone calls.