The Gambia, like most other sub-Saharan African countries, is characterised by significantly incomplete vital registration, which makes it more difficult to carry out field-based medical research, especially studies that require accurate measurement of disease incidence and mortality rates. The prospective demographic surveillance approach, despite its high resource demands, provides the best opportunity to underpin large-scale epidemiological studies and field trials; as well as generate much needed quantitative and qualitative evidence from scientific investigations to formulate or influence policy change with respect to health care delivery systems vis-à-vis an evolving pattern of disease burden in both children and adults.
The Unit maintains three Health and Demographic Surveillance Systems (HDSS), namely Farafenni (from 1981), West Kiang (from 2005) and Basse (from 2007), to serve as platforms for a range of field studies aimed at improving understanding of public health priorities in West Africa in particular and the developing world in general. A fourth one operated from Bansang, and located in the Fulladu West district adjacent to the Basse HDSS, currently supports the Vaccine Impact on Diarrhea in Africa (VIDA) project only, with no firm arrangements to continue surveillance beyond the duration of the study.

The sites represent different geographical and environmental conditions as well as disease ecologies, and therefore collectively constitute a valuable scientific resource for The Unit to underpin its investigations relating to the Sustainable Development Goals (SDG’s) across its three research themes.

Printing, management and storage of the questionnaires have consistently been a significant challenge to Fieldworkers, Data Entry Clerks and Data Managers, with significant chances of introducing error during data entry. Resolution of errors and other queries in the field can be time-consuming.

Electronic Data Capture software was developed by a private consulting firm, InSIST Global, and implemented with support from the Data Management Department. It was rolled out on 1st October 2015 in Farafenni, and 1st March 2016 in Basse.

The immediate advantages of the electronic data capture include organised sequential interview schedule; internal consistency checks, e.g. date logic. This, therefore, implies low error rate, shortened interview time, and potential to increase the scope of routine data collection.

Roll-out was preceded by an independent sample HDSS re-enumeration surveys in Farafenni (4,762 households) and Basse (4,235 households) conducted by a team of 31 female enumerators. The purposes of the re-enumeration were to:

• evaluate the integrity and completeness of the paper-based generated HDSS database;

• demonstrate, as an advancement in demographic methodology, the use of Demographic Health System (DHS) survey technique to independently validate HDSS data;

• estimate neonatal mortality retrospectively as part of a study comparing measurements from different data sources. This constituted part of Dr Anne Rerimoi’s PhD work;

• independently estimate key benchmark indicators for maternal and reproductive health, such as stillbirth and spontaneous abortion rates.

Since the new electronic data capture system is flexible and provides potential to increase the scope of HDSS data collection, plans are being explored to:

1. Establish specific cohorts of interest, as well as sampling frames for different age groups for which necessary biological samples will be collected periodically and processed for detecting parasites, measuring glucose, micronutrients, and any other outcome of interest. This will be particularly suited for detailed prospective community-based studies relating to non-communicable diseases (NCDs), such as diabetes and hypertension.

2. Design and collect relevant health information on adolescents, adults and the elderly, thus enhancing our understanding of the health-related problems and challenges in the entire life course for residents in this part of Sahel West Africa.