Rayto Ca-660: PT reported, INR not calculated
What happened
The coagulation analyzer reports prothrombin time (PT) results but does not calculate INR.
What was checked
- The engineers first asked whether QC control material had been run and passed.
- They then checked whether the reagent lot had been changed and whether the ISI value from the new lot's package insert had been entered.
Cause
The probable cause reported in the case: after a reagent lot change, the ISI value from the new lot's package insert was not re-entered. ISI differs from lot to lot, so with an outdated value the analyzer could not compute INR, while the PT measurement itself kept working.
The cause is probable and was not fully confirmed.
What was done
Enter the current ISI value for the new reagent lot from its package insert into the analyzer's reagent settings, then verify on control material that both PT and INR are calculated.
Safety
Treat patient samples, used cuvettes and reagent waste as potentially infectious material, and complete the required electrical safety test before returning the analyzer to use.
Lesson: When a calculation depends on a lot-specific reagent parameter, a lot change is the first suspect — update parameters such as ISI with every new lot before looking for a hardware fault.
Covered in the course: Lab Analyser Service — Level 2: Fault-Finding →
Written from an anonymised case shared by service engineers. It is not a manufacturer instruction and grants no authorisation. Independent note; names are trademarks of their owners.