Prevalence and causes of iron deficiency anemias in infants aged 9 to 12 months in Estonia.

OBJECTIVE: To investigate the prevalence and causes of iron deficiency anemia in infants aged 9 to 12 months in Estonia. MATERIAL AND METHODS: Every second child aged 9-12 months was randomly selected from primary medical centers in seven counties from all over Estonia. A questionnaire concerning eating habits and lifestyle was sent to their parents. Sixty-five percent (n=195) of contacted families agreed to participate in the study. Mean corpuscular volume and hemoglobin, serum ferritin, and soluble transferrin receptor levels were measured in 171 infants. Anemia was defined when hemoglobin level was lower than 105 g/L, and iron deficiency when ferritin level and mean corpuscular volume were lower than 12 microg/L and 74 fL, respectively. RESULTS: The prevalence of iron deficiency was 14.0% and iron deficiency anemia 9.4%. Birthweight less than 3000 g was the main risk factor for iron deficiency (OR=9.4; P<0.0005). Infants fed with breast milk and solid food had lower ferritin concentration (18.5 microg/L, 95% CI 14.0-23.0) than infants fed with formula and solid food (32.8 microg/L, 95% CI 26.6-39) (P<0.005). CONCLUSION: Iron deficiency anemia is common among 9-12-month-old Estonian infants. The main risk factor for iron deficiency was birthweight less than 3000 g.

Reference and cut-off values for serum ferritin, mean cell volume, and hemoglobin to diagnose iron deficiency in infants aged 9 to 12 months.

BACKGROUND: The number of different laboratory tests and reference values are used to diagnose iron deficiency, but there is no agreement regarding the diagnostic criteria for infants. Aim of study. To establish reference values for serum ferritin, mean cell volume, and hemoglobin in infants aged from 9 to 12 months in Estonia and to evaluate the diagnostic characteristics of serum ferritin, mean cell volume, and hemoglobin in the diagnosis of iron deficiency. METHODS: Altogether 195 healthy infants aged 9-12 months participated in the study. They were randomly selected out of 300 families from seven different counties from all over Estonia. Serum ferritin, hemoglobin, soluble transferrin receptor (sTfR) levels and mean cell volume were measured. The best cut-off values for serum ferritin, mean cell volume, and hemoglobin to diagnose iron deficiency, defined by sTfR>2.45 mg/L (n=25), were determined by receiver operating characteristic curves. RESULTS: The mean and reference values (5th and 95th centiles) for ferritin was 24 microg/L (4-55), 73 fl (68-80) for mean cell volume, and 112 g/L (101-128) for hemoglobin. The best cut-off values to diagnose iron deficiency were <10.9 microg/L for serum ferritin (sensitivity of 83% and specificity of 80%), <71 fl for mean cell volume (86% and 83%, respectively), and <107 g/L for hemoglobin (67% and 87%, respectively). The sensitivity and specificity of serum ferritin and mean cell volume in the diagnosis of iron deficiency were better than those of hemoglobin. CONCLUSION: For the diagnosis of iron deficiency in infants aged 9-12 months, the cut-off values of <10.9 microg/L and <71 fl should be used for serum ferritin and mean cell volume, respectively.

Seroprevalence of IgG antibodies to pertussis toxin in children and adolescents in Estonia.

BACKGROUND AND AIMS: Despite high immunisation coverage and frequent booster doses, the national notification rates of pertussis in Estonia have been increasing. The peak of 97/100,000 was reached in 2010 which is the highest incidence rate since 1962 (210/100,000). We aimed to measure the prevalence of pertussis toxin (PT) IgG type antibodies in subjects of <18 years and to estimate the pertussis infection activity in a recently non-immunised cohort. METHODS: In a cross-sectional serosurvey, all consecutive leftover sera were collected in the Tartu University Hospital during April-August 2012. Anti-PT IgG concentration was measured by commercial ELISA and analysed in yearly cohorts. The antibody concentrations ≥62.5 IU/mL was considered suggestive to pertussis in the last year among 9- to 14-year-olds. RESULTS: The GMC of the anti-PT-IgG was 7.4 IU/mL (95% CI 6.9-8.0). In the total of 1053 serum samples, the highest proportion of sera with high antibody titres ≥125 IU/mL and ≥62.5 IU/mL were at the ages when pertussis vaccine boosters were given: 7 years 10.9% (95% CI 4.1-22.3) and 2 years 36.9% (95% CI 25.3-49.8), respectively. Approximately half of all sera had undetectable anti-PT IgG levels. The estimated incidence of Bordetella pertussis infection among 9- to 14-year-olds in the year before serum sampling was 6.3% (95% CI 3.3-10.8), which is at least 60 times higher than the officially reported incidence of pertussis disease in respective years. CONCLUSIONS: The serologic method is not suitable for diagnosing pertussis in instances when the last pertussis immunisation was less than one year ago. The relatively high proportion of subjects with undetectable anti-PT IgG levels and the relatively low rate of officially reported pertussis cases suggest that low antibody levels do not necessarily indicate the absence of protection. The estimated incidence rate of pertussis is much higher than officially reported figures, which suggests that asymptomatic/mild B. pertussis infection remains unrecognised and unreported.