Quality Assurance and Quality Control in Cohort Studies


Ardeshir Khosravi


Abbas Keshtkar, Sadaf G Sepanlou, Amirabbas Momenan, Arash Ghanbarian, Akram Pourshams


Quality assurance (QA) is any systematic process or activity which is done, mainly before data gathering, to assure that a specific research project being developed meets specific requirements and the errors will be prevented or minimized. In contrast, quality control (QC) is any process or observational activity which is done, throughout a research, including data collection, data cleaning, and data analysis to identify and then, correct any error or fault. In other words, the QC is the observation techniques and activities used to fulfill requirements for quality.

For research purposes, a cohort is any group of people who are linked in some way. In medicine, a cohort study is often undertaken to obtain evidence to try to refute the existence of a suspected association between cause and effect. Since QA and QC are two major and important components of a cohort study, developing a comprehensive guideline or protocols of QA and QC is necessary when a researcher is trying to run a quality cohort study.

The QA in a cohort study has several components including:

  • Developing a precise practical methods and protocols of the study
  • Standardizing the protocols
  • Developing (or choosing) proper questionnaire for data collection and instructions for data collectors
  • Developing specific QA protocols for lab equipments
  • Developing specific checklist for laboratory QA
  • Pilot studies for data collection methods
  • Specific training courses for personnel
  • Developing standards for data banks and other software
  • Establishing local QA organization for every region.

The QC in the Persian Cohort includes the following components:

  • Evaluating executive protocols in the research field
  • Considering inclusion and exclusion criteria constantly for study population
  • Monitoring the data collection process and cleaning the data, locally and globally.
  • Study of validity and reliability of all data collection instruments
  • Running QC for numeric data such as blood pressure and anthropometric measures
  • Running QC for all paraclinic measures
  • Developing an organization chart and flowchart, specifically designed for the study QC and planning a precise timetable for every activity

QA and QC are two important and inevitable strategies to be done to assure the integrity and quality of a cohort study throughout the study. Developing and implementing a comprehensive QA and QC protocols will guarantee the quality and accuracy of data collected in each research study.

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