Quality Assurance and Quality Control in Longitudinal Studies Coralyn W. Whitney, Bonnie K. Lind, and Patricia W. Wahl Epidemiologic Reviews, 1998, Vol. 20, No. 1

Warm-up Questions

Q1. True or False? Quality assurance consists of those activities undertaken before and during the data collection phase.

Q2. True or False? Pilot studies are a part of quality assurance activities

Q3. True or False? Having a quality control supervisor watch an interview is recommended as part of activities to monitor interviewers?

Q4. True or False? Frequently, studies establish procedures for identifying problems but fail to establish adequate procedures for ensuring that the problems are resolved.

Q5. True or False? When an old measuring equipment (e.g. BP measuring device) is replaced by a new one, the date of replacement should be recorded only.

Objective This presentation will suggest ways of minimizing potential sources of error in (cohort) studies.

Quality Assurance quality assurance consists of those activities undertaken prior to data collection to ensure that the data are of the highest possible quality at the time they are collected.

Quality Control? quality control consists of those activities that take place during and after data collection to identify and correct any errors or discrepancies in the data that have been collected

The focus is on Clinical Trials Multiple Risk Factor Intervention Trial Hypertension Primary Prevention Trial Optic Neuritis Treatment Trial What are the differences between C.T and Cohort studies?

QUALITY ASSURANCE ACTIVITES development of the study protocol development of the data entry and data management systems Training and certification of data collection personnel Testing of data collection procedures.

Summary of Q.C. and Q.A. activities Quality assurance activitiesQuality control activities

Summary of Q.C. and Q.A. activities Quality assurance activitiesQuality control activities

Summary of Q.C. and Q.A. activities Quality assurance activitiesQuality control activities

Q.A. Activities Development of the study protocol – Design of data collection instruments, including content, format, and step-by-step instructions for completion of the instrument. – Standard equipment – Procedures for reviewing and updating the protocol – Communication Development of data editing, transcription, and entry procedures (EPI- DATA) Training and certification Testing of procedures self-administered OR Interviewer- administered questionnaires ?

communication Operation Committee Field and Reading centers Quality control committee Coordinating Center

Organization and communication among study personnel

Field center Q.C. Activities – Recruitment – Technician performance – quality control supervisor watch an interview? – Data clean-up – Replicate measures (always?)

Aspects of field center Q.C. unique to cohort studies longitudinal nature of cohort studies: – Staff turnover – Technician drift – Degradation of equipment – Technology/Software change – Inconsistencies in participant responses over time Frequent central training and retraining sessions + Scientific sessions +

Quality control of reading centers and laboratories Often the data processed at such centers or laboratories are the key exposures or outcome variables for the study. Calibration set repeat studies on a subset of participants analyses of data processed at a reading center or laboratory over time

Q.C. and recruitment report responsibilities and distributions TABLE 2

When a problem is identified, several steps are needed to solve the problem and correct the data… Check for possibility of statistical adjustment

SUMMARY Cohort studies are typically large-scale designs Involve an extensive amount of data to be collected and processed data are collected over an extended period of time and at several centers Q.C. tasks are delegated to various committees, so good communication is mandated

In conclusion The magnitude of the quality control process in a multicenter longitudinal study should not be underestimated, requiring a significant commitment of study resources.

Now try warming up questions again …