Statistical quality control is the discipline of running known control materials alongside patient samples and using the results to decide whether an instrument is reliable enough to produce patient values — and in a clinical lab, the QC module of the LIS is where those controls are evaluated, reviewed, and documented. Daily QC protects patients when a failed control is unmistakable during result review and the lab can apply its hold and investigation procedure from the same system.
This post takes the operational angle: how a clinical LIS turns Levey-Jennings charts and Westgard rules into failed-QC alerts, review evidence, and SOP-controlled sample holds.
Quick answer
A clinical LIS runs statistical QC by posting each control value to Levey-Jennings charts and evaluating the Westgard multirule set as results are saved. LIMS IQ records the failed rule, alerts patient-result reviewers when a run has non-passing QC, and lets the lab place affected samples on hold under its SOP while it investigates, supporting CLIA quality-control expectations.
What the QC rules actually catch
Quality control exists to catch two kinds of error before they reach a patient report, and a Levey-Jennings chart makes both visible at a glance:
- Random error — scattered control values and one-off outliers, the signature of imprecision. A single control point far from the mean is the classic flag.
- Systematic error — drift the instrument introduces gradually. A shift is a run of control points sitting on one side of the mean (often a reagent lot change or a recalibration); a trend is points marching steadily in one direction (often a degrading lamp, electrode, or reagent).
The chart plots each control against the analyte’s established mean and standard-deviation limits over time, so a tech scanning recent points can see a shift or trend forming. The point of running the rules in the LIS is that the system flags these patterns automatically as controls post, rather than relying on a person to notice them on a printout at the end of the shift.
The Westgard multirule set
Westgard rules are the standard framework for turning “how far is this control from the mean?” into an in-or-out-of-control decision. LIMS IQ evaluates the multirule set and lets each lab select rules and warning-versus-fail severity for each QC level lot:
- 1-2s — one control value beyond 2 SD. A warning rule that triggers inspection of the others, not an automatic rejection on its own.
- 1-3s — one control value beyond 3 SD. Detects large random error; a rejection rule.
- 2-2s — two consecutive control values beyond the same 2 SD limit. Detects systematic error.
- R-4s — a 4 SD range between two controls in a run. Detects random error within the run.
- 4-1s — four consecutive control values beyond the same 1 SD limit. Detects smaller systematic shifts.
- 10-x — ten consecutive control values on the same side of the mean. Detects sustained drift a single-point rule would miss.
The reason the rules are configurable per control lot matters operationally: applying the full multirule set everywhere raises false rejections on assays that do not need that sensitivity, while applying too loose a set on a regulated quantitative method misses real error. LIMS IQ also scopes quantitative limits by analyte, equipment type, and method, so different platforms can use the targets and rules the laboratory configured for them.
Failed QC: from alert to an SOP-controlled hold
The single most important thing an LIS does with QC is not draw the chart — it is make a failed control unmistakable in the patient-review workflow. A patient value can look completely normal and still be wrong if the instrument that produced it was out of control.
LIMS IQ evaluates each saved QC result against the active limits and Westgard rules, stamps its status, and records the specific rule that failed. During batch review, a failed-QC alert tells the reviewer that the associated testing run has non-passing controls and provides access to the run’s QC evidence. If the lab’s SOP requires a hold, the reviewer can place the affected samples on hold so they cannot complete until the investigation is resolved.
The disposition after a failure — repeat the control, recalibrate, repeat patient testing, hold, or release with documentation — remains the laboratory’s decision. The LIS supplies the evaluation, visible alert, linked evidence, and hold control needed to execute that decision consistently.
Review and corrective documentation
A flagged QC run is the start of a workflow, not the end of one. Pending QC results sit in a review queue and can be marked reviewed individually or in batch, with the reviewer and date retained. Reviewers can add comments, edit a result when appropriate, or exclude a documented outlier from charting with an ignore action and comment rather than deleting the point.
After a chart period is reviewed, its approval is archived as a PDF tied to the analyte, instrument, control lot, and date range. Approval-history, summary, and daily-QC reports keep the review evidence available for inspection alongside the failed-rule detail and comments on individual results.
CLIA and CAP expectations
QC is not optional documentation; it is a regulated obligation. CLIA quality-control requirements under 42 CFR Part 493 Subpart K expect labs to run controls at defined frequencies, document the results, and act on failures with corrective action and supervisory review. CAP accreditation checklists carry the same expectations in inspection-ready form, and labs using risk-based plans operate them under CLIA’s Individualized Quality Control Plan (IQCP) framework.
An LIS supports these by making documentation a byproduct of the workflow rather than a separate clerical task: every control value and rule evaluation is recorded, failed rules remain attached to their results, reviews identify who acted and when, comments and chart exclusions stay documented, and approved charts are archived. Demonstrating the QC record is a matter of following the evidence the system already kept.
Where LIMS IQ fits
LIMS IQ connects QC evidence to patient-result review rather than leaving it in a parallel record. The platform supports:
- Levey-Jennings charts with mean and ±1, ±2, and ±3 SD bands, failed points highlighted, multi-instrument overlays, and PDF output.
- Configurable Westgard multirules assigned per QC level lot, with warning-versus-fail severity and evaluation priority.
- Immediate QC evaluation that records Pass, Warning, Fail, No Limits Defined, or QC Limit Expired and retains the specific failed rule.
- Patient-review visibility that links testing runs to their QC evidence and visibly alerts batch reviewers to failed or non-passing QC.
- SOP-controlled sample holds that block completion until the laboratory releases the hold after investigation.
- Documented review with reviewer/date stamps, comments, transparent chart-point exclusions, and archived chart approvals.
- Exception reporting for samples on hold or associated with failed QC.
The product surface lives on the QC LIS module page; QC sits inside the broader clinical LIS result-review workflow, and the bench-level detail is in the chemistry LIS and hematology LIS guides. The QC pass-rate and fall-out metrics that summarize control performance over time belong on the analytics for clinical labs dashboard.
Frequently asked
What are Westgard rules and how does an LIS apply them? Westgard rules are a multirule set of statistical control criteria — including 1-2s, 1-3s, 2-2s, R-4s, 4-1s, and consecutive-value rules — that evaluate how far control values sit from the established mean in standard-deviation units. LIMS IQ applies the rules automatically as each control result is saved, records the specific failed rule, and surfaces a Pass, Warning, Fail, No Limits Defined, or QC Limit Expired status. Each control level lot can carry its own selected rules and warning-versus-fail severities.
What happens when QC fails in LIMS IQ? LIMS IQ automatically records the failed rule and marks the QC result as non-passing. During patient batch review, the QC control changes state when the associated run contains failed QC so reviewers can open the run’s QC evidence before release. When the laboratory’s SOP calls for it, affected samples can be placed on hold, which blocks completion until the hold is released after investigation. The lab decides whether to repeat, recalibrate, hold, or release with documentation.
How do Levey-Jennings charts detect instrument drift? A Levey-Jennings chart plots each control value against the analyte’s established mean and standard-deviation limits over time. Random error shows up as scattered points and outliers; systematic error shows up as a shift (a run of points on one side of the mean) or a trend (points marching steadily in one direction). Because the LIS posts controls to per-analyte, per-instrument charts in real time and runs the Westgard rules against them, drift becomes visible — and actionable — before it accumulates into a patient-result problem rather than after.
How does QC connect to patient-result review? QC evidence is linked to the patient testing run rather than stored in a separate silo. Reviewers can open the associated QC results from the patient review worklist, and batch review visibly alerts them when the run contains failed or non-passing QC. Affected samples can then be placed on hold when the laboratory’s SOP requires it, while the final disposition remains a documented laboratory decision.
How does LIS-based QC support CLIA and CAP compliance? CLIA quality-control requirements under 42 CFR Part 493 Subpart K and CAP accreditation checklists expect labs to run controls at defined frequencies, document QC results, and act on failures. LIMS IQ retains each control value, status, failed rule, reviewer and review date, comments, documented chart-point exclusions, configuration history, and archived chart approvals. That record lets an inspector follow a failed control through the lab’s documented review without relying on a separate spreadsheet or paper chart.
Can QC rules differ by control lot and instrument? Yes. Each QC level lot can be assigned its own Westgard rule set, including warning-versus-fail severity and evaluation priority. Quantitative mean and SD limits can also be scoped by analyte, equipment type, and method, so different platforms are evaluated against the targets and control logic the laboratory configured for them.
Next steps
- See the QC LIS module feature page for the product surface — Levey-Jennings charts, Westgard rules, failed-QC alerts, review, and archived approvals.
- Read the autoverification rules post for how result-release rules route exceptions for review.
- Review the chemistry LIS and hematology LIS guides for how QC plays out on each bench.
- See the FISH probe lot tracking and QC guide for a separate cytogenetics review workflow.
- Browse the rest of the clinical laboratory informatics series — LOINC mapping, critical-value callbacks, ELR reporting, and lab KPI dashboards.
- Or, fastest path: request a demo and walk through your QC rules, review, and hold policy with our team.