Internal Quality Control in Medical Labs

Internal Quality Control in Medical Labs: Internal quality control, often called IQC, checks whether a test process remains sufficiently stable to support patient result reporting. It differs from external quality assessment and from method validation.

Why this topic matters: A control result is useful only when acceptance rules and responses are established before patient reporting.

Step 1 — Scope the problem: Identify suitable control materials and levels for each examination system, based on manufacturer guidance and laboratory risk.

Step 2 — Apply the method: Set acceptance and rejection rules, evaluate trends and shifts, and define what happens when a run fails.

Step 3 — Sustain the result: Document patient-result impact assessment, repeat testing or recalibration where justified, followed by review of recurring failures.

Practical laboratory example: A biochemistry control shifts after a reagent lot change while results remain technically inside one wide limit. A trend review may identify the issue earlier than a pass/fail glance.

Common errors: Repeating controls until one passes without investigating, ignoring shifts, or using a single limit for unrelated analytes. Procedures need to withstand real laboratory conditions and staff turnover, rather than merely look complete during audits.

Evidence to keep: Control charts, lot-change assessments, QC review decisions, corrective actions and authorised release evidence. The records should allow an independent reviewer to reconstruct how and why technical decisions were made.

Action to take this week: Review the last month's rejected controls and check whether each decision is traceable. Assign an owner and decide what evidence will demonstrate improvement.

Authoritative references: ISO 15189:2022 and test-specific professional laboratory guidance. Always obtain the applicable standard and check its scope before interpreting this educational overview as an accreditation requirement.