Opportunistic sampling from early childhood centres: a substitute for random sampling to determine lead and iron...

Area of Science:

• Environmental Health
• Pediatric Public Health
• Nutritional Epidemiology

Background:

• Elevated blood lead concentrations and iron deficiency are significant public health concerns in young children.
• Accurate prevalence data is crucial for targeted interventions and public health policy.
• Assessing the efficacy of different sampling strategies is vital for efficient public health surveillance.

Purpose of the Study:

• To compare the effectiveness of stratified random sampling versus opportunistic sampling via Early Childhood Centres (ECCs) for assessing blood lead levels and iron status in Sydney children aged 12-36 months.
• To determine if opportunistic sampling can serve as a viable alternative to traditional random sampling methods for pediatric health surveillance.

Main Methods:

• Two sampling strategies were employed: stratified random sampling using census districts and opportunistic sampling using ECC client registers.
• Blood lead concentrations and iron status (plasma ferritin) were measured in children aged 12-36 months.
• Statistical analyses compared prevalence rates and geometric means between the two sampling groups.

Main Results:

• Random sampling yielded higher response rates (75.3%) compared to opportunistic sampling (24.1%).
• Significantly higher proportions of children with elevated blood lead concentrations (>0.48 and >0.72 mumol/L) were identified via random sampling.
• No significant differences were found in the prevalence of iron depletion, iron deficiency, or iron deficiency anemia between the two methods.

Conclusions:

• Opportunistic sampling through ECCs is not a substitute for random sampling surveys when determining the prevalence of elevated blood lead concentrations in preschool children.
• Opportunistic sampling via ECCs may be appropriate for monitoring iron status, particularly iron depletion, in preschool children.