Planning and Organising an Epidemiological Study
Core Idea
- An epidemiological study must be carefully planned before data collection begins.
- Good planning ensures the study is reliable, representative and scientifically valid.
- Results are used for prevention programmes, healthcare planning and public health decision-making.
Basic Stages of an Epidemiological Study
- Every epidemiological study follows four major stages:
- Programme-plan – Data collection – Processing & analysis Final report
Stage I — Programme-Plan
- Most important stage because mistakes here affect the entire study.
- Determine:
- Purpose and object of study.
- Subject of investigation.
- Aim, tasks and working hypothesis.
- Example:
- Dental caries in 12-year-old children.
- Determine units of study:
Logical unit
- Observed individual: person, patient, child, 12-year-old student.
Technical unit
- Place where logical unit is located: school, village, city, clinic.
- Determine:
- Time of study – Place of study – Observation period.
- Select indicators:
- DMFT – CPI – Caries prevalence – Oral hygiene indices.
- Prepare:
- Questionnaires – Registration forms – Recording sheets.
- Organise resources:
- Funding – Personnel – Equipment – Time Determine sample size and sample structure.
Sampling and Representativeness
- Sample must accurately represent the population.
Complete study
- Entire population examined.
Representative study
- Only selected sample examined.
- Representative studies are used more often because they are:
- Faster – Cheaper – Easier to organise – Still reliable.
- Subjects should be selected objectively and randomly whenever possible.
Examiner Calibration
- Before data collection, examiners undergo training called calibration.
- Purpose:
- Standardise diagnostic criteria.
- Reduce examiner variation.
- Improve reliability and validity.
- Ensures different examiners record findings in the same way.
Stage II — Conducting the Study
- Collect primary data according to the programme-plan.
- Use:
- Standardised criteria – Standardised indices – Standard
examination methods.
- Maintain quality control throughout the investigation.
- Data collection methods:
- Clinical examinations – Questionnaires – Interviews Existing records.
Stage III — Processing and Analysis
- Check data for completeness and accuracy.
- Group data according to:
- Age – Sex – Residence – Occupation.
- Calculate:
- Prevalence – Intensity – Mean values – Percentages.
- Compare groups and identify:
- Trends – Risk factors – Population differences.
- Statistical analysis is performed using medical statistics.
- Common software:
- SPSS
Stage IV — Results and Final Report
- Prepare:
- Final report – Scientific article – Dissertation – Presentation.
- Include:
- Results – Discussion – Conclusions – Recommendations.
- Findings guide:
- Prevention programmes – Health promotion – Service
planning – Public health policy.
Importance of Epidemiological Studies
- Assess population health status.
- Identify disease risk factors.
- Evaluate prevention programmes.
- Assess effectiveness of treatment methods.
- Determine healthcare needs and resource allocation.