CAP Preventive Maintenance Log Requirements
4 min read
Preventive maintenance (PM) findings are among the most common CAP citations — not because labs skip maintenance, but because the maintenance happens and the log doesn't fully capture it. Here's what a defensible PM log actually needs.
The minimum elements of a complete PM record
For every completed PM event, at minimum:
- Instrument identifier — including serial number, not just model, since labs frequently run more than one of the same analyzer
- Task performed — matched to the manufacturer's defined checklist item, not a generic "PM completed" note
- Date and time performed
- Who performed it — and that person's competency for the task should be on file separately
- Result of each check — pass/fail against a defined tolerance where applicable, not just a checkmark
- Any corrective action taken, if a check failed, plus re-verification after the fix
A PM log that says "monthly PM — done — 3/14" for an instrument whose manufacturer schedule includes six distinct monthly tasks doesn't actually demonstrate all six were performed — it demonstrates that someone believes they were.
Matching the log structure to the manufacturer's schedule
The manufacturer's service manual defines the PM tasks and their frequency (daily, weekly, monthly, quarterly, annual). The lab's PM log should mirror that structure directly — one line per task, not one line per visit — so that "was the six-month optical alignment check done in Q2" is a direct lookup, not something reconstructed from a narrative note.
How far back inspectors typically look
CAP inspections commonly review PM records for the full accreditation cycle since the last inspection (typically two years), with particular attention to any gaps, especially around instrument downtime events or periods of staffing turnover. A single missing entry from three years ago is less concerning than a pattern of gaps clustering around a specific timeframe — which reads as a systemic issue rather than a one-off.
Common findings and what causes them
Gaps with no explanation. A missing monthly PM record with no note about why (instrument down for repair, task performed but not logged, task genuinely missed) reads worse than a documented miss with a corrective note, because it signals the log itself may be incomplete elsewhere too.
PM performed but not tied to the right instrument. In labs running multiple units of the same analyzer model, records that don't specify serial number make it impossible to confirm each individual instrument received its required maintenance.
"Done" without the actual check result. A monthly PM task that includes an optical or mechanical tolerance check needs the actual measured value or pass/fail result recorded — not just confirmation that the check was performed.
Downtime-triggered PM not distinguished from scheduled PM. When an instrument goes down unexpectedly and maintenance is performed as part of the repair, that event should be logged distinctly from the routine schedule, with a clear note on what triggered it and what verification confirmed the instrument was safe to return to service.
A practical log structure
| Instrument (incl. serial) | Task | Scheduled frequency | Date completed | Performed by | Result | Corrective action (if any) |
|---|---|---|---|---|---|---|
| Analyzer A — SN 44821 | Optical alignment check | Monthly | ||||
| Analyzer A — SN 44821 | Fluidics cleaning | Weekly | ||||
| Analyzer A — SN 44821 | Full system PM (annual) | Annual |
The pattern behind most PM findings
The maintenance itself is rarely the problem — technicians generally do the work. The finding happens when the log can't independently prove the work was done, to the specific standard, on the specific instrument, at the required frequency, without someone's memory filling in the gaps. A log tied to the instrument record itself, structured around the manufacturer's actual task list rather than a generic monthly note, closes that gap by construction rather than by discipline alone.