Lecture 6

• Quality control

  A set of activities, techniques, and processes aimed at identifying and addressing defects and deviations from the desired quality standards
• Quality assurance

  Encompasses the proactive and systematic activities designed to prevent defects and ensure that the desired quality standards are consistently met
• Quality management system

  A formalized system that documents processes, procedures, and responsibilities for achieving quality policies and objectives
• Quality system encompasses both quality assurance and quality control
• Quality assurance has been defined by the WHO as "the total process whereby the quality of laboratory reports can be guaranteed"
• Quality assurance (summarized)


  The right result, at the right time, on the right specimen, from the right patient, with the result interpretation based on correct reference data, and at the right price
• Sample type plays a role in quality assurance
• Quality control must cover all aspects of every procedure within the department
• Quality control must be practical, achievable, and affordable
• All materials, equipment and procedures must be adequately controlled in quality control
• Quality assurance

  • Focuses on preventing defects by establishing robust processes, conducting audits, and implementing corrective and preventive actions
  • Integrated into the entire process from start to finish
  • Involves process design, documentation, training, audits, and continuous improvement efforts
  • Process-oriented, addressing the entire system
• Quality control

  • Focuses on detecting and rectifying defects
  • Performed after production or service delivery
  • Activities include inspection, testing, and measurement
  • Quality control is product-oriented, focusing on specific outputs
• Quality assurance should come first when setting up a lab
• Quality assurance and quality control concepts are relevant to microbiology
• Quality assurance and quality control concepts affect antimicrobial susceptibility testing
• Application of quality assurance

  • Pre-analytical
  • Analytical
  • Post-analytical
• ISO 15189:2022 accreditation


  Accreditation standard for medical laboratories
• EQA programmes and CAP are examples of quality assurance programmes
• Media quality control

  1. Culture media must be tested for sterility and performance

  2. Performance checked by growth, expected reactions and zone sizes

  3. Control strains and antibiotics used
• Meuller-Hinton media

  • pH 7.2 - 7.4
  • 6 discs on 90 mm plates
  • 12 discs on 150 mm plate
• Macrolides, aminoglycosides and quinolones have decreased activity in low pH Meuller-Hinton media
• Tetracyclines have increased activity in low pH Meuller-Hinton media
• Thymidine & thymine imbalance can cause false resistance in Meuller-Hinton media with sulfamethoxazole-trimethoprim
• Increased Ca2+ and Mg2+ in Meuller-Hinton media can cause false resistance
• Decreased Ca2+ and Mg2+ in Meuller-Hinton media can cause false susceptibility
• Specimen collection, transport, processing and reporting

  1. Collection must ensure the best possible specimen is collected in a repeatable manner

  2. Lab must have fixed cut off times, conditions and short term storage of specimen

  3. Processing follows SOPs
• Mishandling of a specimen in the pre-analytical phase can have deleterious outcomes on the yield of a potential pathogen