Challenges in identifying the methodology to estimate the prevalence of infectious intestinal disease in Malta

Routine surveillance systems capture only a fraction of infectious intestinal disease (IID) that is actually occurring in the community. Different methodologies utilized among various international studies in the field were reviewed in order to devise an appropriate survey to obtain current estimates of prevalence of IID in Malta. An age-stratified retrospective cross-sectional telephone study was selected for the study due to its feasibility in terms of limited resources necessary (funds, time and human). The disadvantages of this type of study include the inherent biases such as selection bias (sampling, ascertainment and participation bias) and information bias (recall and observer bias). A pilot study was carried out using a random age-stratified sample of 100 persons over a 3-month period. A total of 5.0% (95% CI +/-4.27) of the population was estimated to have suffered from IID during that period. This estimate was used in order to assist in sample size calculations for a large-scale community study. It also served to test the survey instrument and methodology and to identify operational problems.