How Are CCI Positive Results Classified
Result classification is the first and most consequential decision in a CCI control strategy. Classification determines whether a result requires a retest, a full investigation, a lot hold, or immediate escalation to QA leadership — and it must be completed before any of those actions can begin.
Why does classification matter before any other action?
Because the appropriate response to a borderline result and the appropriate response to a gross failure are completely different. Treating every positive identically — either retesting everything or holding everything — is both scientifically indefensible and operationally unsustainable. Classification provides the scientific basis for proportionate action.
What are the five result classes?
Class 1 — Clear Pass: Result well within specification. Standard documentation only.
Class 2 — Borderline: Result recorded as a failure by the instrument but falling within one additional standard deviation above the validated pass/fail threshold. Warrants instrument challenge and up to two retests.
Class 3 — Clear Fail: Result exceeds the borderline zone. An unambiguous positive signal. Unit is quarantined; formal investigation is initiated; production is halted pending instrument challenge.
Class 4 — Invalid:Instrument error or environmental anomaly may have caused a spurious result. The result cannot be used for disposition. Instrument must be re-qualified before any testing resumes.
Class 5 — Systemic: Multiple positives within a batch or subgroup indicating a process excursion. Lot hold is mandatory; QA leadership is notified immediately; expanded sampling is required.
How is the borderline zone defined technically?
PTI pass/fail thresholds are placed at a minimum of 4σ above the negative control mean — 6σ for regulated sterile pharmaceutical applications. Class 2 spans from that threshold to one additional standard deviation above it. Class 3 begins beyond that boundary. Both are recorded as instrument failures; classification is a QA post-result interpretation of failure magnitude, not a separate instrument output category.
What must happen before classification leads to retest?
The instrument must pass a five-step challenge: a confirmed negative control must pass, a confirmed positive control must fail at its expected signal level, environmental conditions must be within the validated range, the test chamber must show no visible anomaly, and the correct method recipe must be confirmed as loaded. If the instrument fails any step, all units tested since the last confirmed passing control are quarantined — and no retest occurs until the instrument is re-qualified.