As-Found / As-Left
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A definition is SPEQ’s plain-language decode of how a term is used in practice, cited to the documents that define it. It is a practitioner reference, not legal or regulatory advice, it does not replace the definition in the source, and where a regulator’s wording differs the regulator’s wording governs.
The pair of calibration readings recorded before any adjustment (as-found) and after it (as-left). The as-found value is the one with GMP consequence: if it is outside tolerance, every result the instrument produced since its last calibration is in question and an impact assessment is required.
As-found is the reading taken before any adjustment; as-left is the reading after. Both are recorded at every calibration, and the asymmetry between them is the whole point: as-left tells you the instrument is now correct, which is reassuring and of little evidential value, while as-found tells you whether it was correct throughout the period just ended, which is the question every result it produced depends on.
An out-of-tolerance as-found therefore triggers an impact assessment, not merely a recalibration. Every measurement the instrument made since its last calibration is in question, and answering that question requires knowing which batches, tests or environmental records it touched — which is why the asset register and the calibration record have to be joinable. Organisations discover the limits of their own records at exactly this moment.
The direction and magnitude matter too. An instrument reading low on a critical upper limit has a different product consequence from one reading high, and an assessment that reports only "out of tolerance" has not yet said anything about product.
- —As-found is before adjustment; as-left is after.
- —As-found carries the GMP consequence — it describes the period just ended.
- —Out-of-tolerance as-found triggers impact assessment over every result since the last calibration.
- —That assessment needs the asset register and calibration record to be joinable.
- —Direction and magnitude of the error determine the product consequence.
EU GMP Part I Chapter 3 (§3.41 calibration); 21 CFR 211.68 and 211.160(b)(4); MHRA GxP Data Integrity Guidance (2018).
Frequently asked questions
What is As-Found / As-Left?
The pair of calibration readings recorded before any adjustment (as-found) and after it (as-left). The as-found value is the one with GMP consequence: if it is outside tolerance, every result the instrument produced since its last calibration is in question and an impact assessment is required.
Which regulations cover As-Found / As-Left?
EU GMP Part I Chapter 3 (§3.41 calibration); 21 CFR 211.68 and 211.160(b)(4); MHRA GxP Data Integrity Guidance (2018).