Quality assurance (QA) in histopathology is a systematic program of monitoring, evaluation, and improvement that covers every step from specimen reception to final report issuance. It is required for laboratory accreditation and is fundamental to patient safety.
Internal Quality Control
Internal quality control (IQC) is performed daily within the laboratory. For tissue processing, IQC includes monitoring reagent temperatures, processing cycle times, and paraffin quality. For sectioning, section thickness is verified by visual inspection and micrometers. For staining, control slides with known reactivity are included in every staining run — H&E controls assess nuclear and cytoplasmic detail; special stain controls confirm that the chemical reaction worked correctly (e.g., a control slide known to contain fungi for GMS stain). IHC controls are particularly rigorous: each run includes a positive control (tissue known to express the target antigen) and a negative control (same tissue with primary antibody omitted or replaced by non-immune serum).
External Quality Assessment
External quality assessment (EQA), also known as proficiency testing, compares a laboratory’s performance against peer laboratories. For histopathology, EQA programs cover staining quality (H&E, special stains, IHC), diagnostic accuracy (circulated cases for diagnosis), and reporting completeness. In the UK, UK NEQAS (National External Quality Assessment Service) runs programs for cellular pathology. In the US, the CAP Laboratory Accreditation Program includes proficiency testing. Participation in EQA is mandatory for accreditation in most jurisdictions.
Diagnostic Accuracy and Turnaround Time
Diagnostic accuracy is monitored through random case review (a percentage of cases re-reviewed by a second pathologist), clinicopathological correlation conferences (radiology-pathology and surgical-pathology correlation), and discrepancy tracking (discrepancies between frozen and permanent diagnoses, between original and review diagnoses). Turnaround time (TAT) is measured from specimen receipt to verified report. Routine histology TAT targets are typically 2-5 working days; urgent specimens and frozen sections have same-day TAT targets.
Laboratory Accreditation
Accreditation is a formal recognition that a laboratory meets defined quality standards. Major accrediting bodies include the College of American Pathologists (CAP), the Joint Commission (USA), the United Kingdom Accreditation Service (UKAS) through ISO 15189, and national pathology societies. Accreditation requires documented policies and procedures, personnel qualifications, equipment maintenance records, QA indicators, and participation in EQA.
Risk Management and Error Prevention
Specimen misidentification is the most serious risk in histopathology. Prevention measures include barcode labeling at every step (specimen container, cassette, slide, report), two-patient-identifier checks, and electronic tracking systems. Root cause analysis is performed for serious incidents (wrong patient, wrong diagnosis, lost specimen). Near-miss reporting without blame encourages transparency. Mandatory slide retention periods vary — typically 10-20 years for paraffin blocks and 5-10 years for slides.
Laboratory Information Systems
The laboratory information system (LIS) tracks specimens from accessioning through reporting. Features include barcode tracking, voice recognition for dictation, image management (whole slide images, gross photos), synoptic reporting templates, and automated result interfaces to electronic health records. Digital pathology integration allows remote reporting, teleconsultation, and computer-assisted image analysis.
Personnel Competency
All laboratory personnel undergo initial training and annual competency assessment. Pathologists participate in continuing medical education and revalidation. Histotechnologists demonstrate proficiency in sectioning, staining, and IHC through practical examinations and EQA performance. Regular multidisciplinary team meetings and case conferences maintain diagnostic standards.
