APH 2009, 67, 116-127:

A longitudinal study on the Ghislenghien disaster in Belgium: strengths and weaknesses of the study design and influence on response rate

A. Versporten, E. De Soir, E. Zech, H. Van Oyen

Keywords: technological disaster, exposure classification, gas explosion, longitudinal study, response rate

Background
A longitudinal study was conducted in order to assess the impact of the Ghislenghien disaster ( Belgium) on physical, mental and social health, and to evaluate the prevalence of Post-Traumatic Stress Disorder (PTSD) in the affected population.

Objectives
To describe the set up of the study, to report on the strengths and weaknesses of the methodology employed and its influence on response rate. To clarify the importance of the study for the management of disasters.

Methods/Design
The study included adults (≥ 15 years) and children (8-14 years) at risk of developing adverse health effects related to the disaster. Subjects were connected to the disaster through their geographical or professional proximity as well as connections through relatives. Questionnaires were sent by regular mail 5 months and 14 months after the disaster. Pearson Chi square tests were used to investigate whether the response rate at 14 months depended on the exposure classification.

Results
The response rate at household level was respectively 18% (n=607 families) and 56% (n=338 families) 5 months and 14 months after the disaster. Response rate at the follow up period did not significantly differ by exposure classification.

Discussion
This paper discusses the difficulties and challenges encountered during the design of the study. It discusses the determinants of response in relation to disaster related characteristics. It further provides an overview of lessons learnt and the significance of the study for the management of large scale emergencies.