internal quality control (IQC)

Internal quality control is the routine use of control materials and associated decision rules to monitor whether an examination procedure remains sufficiently stable for its intended use. Control results help detect changes such as shifts, trends, or increased random variation before unreliable patient results are released. They complement calibration, maintenance, external assessment, and other checks rather than replacing them.

A laboratory selects control levels, frequency, acceptance rules, and responses according to examination performance and patient risk. Materials should challenge clinically relevant concentrations where feasible. Assigned targets and limits need a defensible basis, including assessment of new lots. When a control rule fails, staff investigate the cause and assess affected patient results; repeatedly rerunning controls until one passes is not an adequate response.

For accreditation, IQC records demonstrate how staff decide whether examination results can be released. Assessors need more than charts: they look for justified plans, timely review, documented troubleshooting, and decisions about potentially affected patients. Control frequency should reflect the method, workload, stability, and consequences of an undetected failure rather than convenience alone.