Opportunistic sampling from early childhood centres: a substitute for random sampling to determine lead and iron status of pre-school children?

Frequency of hypoferritinemia, iron deficiency and iron deficiency anemia in outpatients

The prevalence rates of hypoferritinemia (IDec/one abnormal indicator), iron deficiency (IDef/two abnormal indicators) and iron deficiency anemia (IDA) in children who were referred to the outpatient clinics of the Department of Pediatrics for the first time within 1 month were investigated. Exclusion criteria were iron therapy before and during the study period and a history of chronic illness. Acute-phase reactants, such as erythrocyte sedimentation rate and C-reactive protein levels, were measured in all cases indicative of infectious diseases. Blood samples were obtained from each study patient admitted to the outpatient clinics during the study period. The hospital charts were later further evaluated, and samples of patients with any current illness known to interact with the iron status of the patient were discarded, and patients were contacted to supply new samples about 1 month after treatment of the infection. Thus, in patients with indications of an infection, samples obtained 1 month after treatment were assessed. The children (n = 557) were divided into four age groups: those aged 4 months to 2 years (group I), 2-6 years (group II), 7-12 years (group III) and 12-18 years (group IV). Children with a decrease in serum ferritin levels without anemia (IDec), and those with lower ferritin, transferrin saturation (TS) and serum iron (SI) concentration (IDef) were evaluated. IDA was diagnosed if hemoglobin (Hb) concentrations were lower than those adjusted for age, ferritin <12 ng/ml and TS <or=16% and if SI was decreased. IDec, IDef and IDA were detected in 26, 11.1 and 12.7% of the patients, respectively. Only 50.1% of the patients visiting the outpatient clinics were found to be normal. The rates of IDec (28.9%), IDef (21.9%) and IDA (26.2%) were highest in group I. IDec had the highest percentages in all groups. In group I, the rates of IDec, IDef, and IDA were 37.2, 66.1 and 69%, respectively. SI concentration was abnormal in 77.1% of the cases in group I (4 months to 2 years of age). Half of the patients referred to the outpatient clinics were suffering from abnormalities related to lower SI concentrations. Close monitoring and treatment of iron deficiency is advised especially in early childhood.

Understanding sampling: representativeness matters

Sampling, or selecting a group of people to represent a whole population, lies at the heart of almost all research designs. There are many ways of going about this, each of which presents its own problems. The trick is to obtain a good-sized sample that is truly representative of the population as a whole.

Iron deficiency in Australian-born children of Arabic background in central Sydney

OBJECTIVES

To determine the prevalence of iron depletion and deficiency, and iron-deficiency anaemia, along with risk factors for iron depletion, in Australian-born children aged 12-36 months of Arabic-speaking background.

DESIGN

Community-based survey.

SETTING

Central Sydney Area Health Service (CSAHS), NSW, April to August, 1997.

PARTICIPANTS

All children born at five Sydney hospitals between 1 May 1994 and 30 April 1996, whose mothers gave an Arabic-speaking country of birth and resided in the area served by the CSAHS.

MAIN OUTCOME MEASURES

Full blood count (haemoglobin, mean corpuscular haemoglobin, mean corpuscular volume), plasma ferritin concentration, haemoglobin electrophoresis, potential risk factors for iron depletion.

RESULTS

Families of 641 of the 1,161 eligible children were able to be contacted, and 403 agreed to testing (response rate, 62.9% among those contacted). Overall, 6% of children had iron-deficiency anaemia, another 9% were iron deficient without anaemia, and 23% were iron depleted. Multiple logistic regression analysis showed three significant independent risk factors for iron depletion: <37 weeks' gestation (odds ratio [OR], 5.88, P=0.001); mother resident in Australia for less than the median time of 8.5 years (OR, 1.96, P=0.016); and daily intake of >600 mL cows' milk (OR, 3.89, P=<0.001).

CONCLUSION

Impaired iron status is common among children of Arabic background, and targeted screening is recommended for this group.