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Reporting accuracy only among valid IVD results may hide how often the first attempt produces an answer. Causes of invalidity and retest burden form part of the real-use question. Distinguish eventual result availability from first-attempt success.
Define the assessment
Define invalidity codes that can distinguish device, specimen, user and unknown causes, while retaining confidence in the assigned reason. First attempts, same-specimen repeats and new collections create different operational and participant burdens. Do not hide them within one test count.
Worked example
For example, some of a hundred specimens initially give invalid results. Retesting resolves several, but others need new collection. The team does not use only final valid results to imply a flawless process. It reports initial invalidity, repeat counts and unresolved cases, with appropriate technical assessment of causes.
Practical checks
- Link the initial attempt and every repeat within the same specimen pathway.
- Record whether the assigned cause is confirmed, suspected or unknown.
- Assess new-collection needs and delayed-result burden within the research context.
Decision and limitations
The report should show valid-result accuracy alongside the pathway to obtaining a result. Not every invalidity is a device failure, but eventual success does not erase the first problem. Route patterns across users and sites into technical assessment and explain unplanned repeats without altering historical records.
Frequently asked questions
- Does a valid repeat erase the original problem?
- No. Final availability and first-attempt status provide different information.
- Are all invalid results caused by the device?
- Do not assume this. Investigate specimens, users and conditions through evidence.