The comparison of mixed distribution analysis with a three-criteria model as a method for estimating the prevalence of iron deficiency anaemia in Costa Rican children aged 12-23 months

Background A maximum likelihood method of mixed distribution analysis (MDA) is presented as a method to estimate the prevalence of iron deficiency ana emia (IDA) in Costa Rican infants 12-23 months old. MDA characterizes the p arameters of the admixed distributions of iron deficient anaemics and non-i ron-deficient-anaemics (NA) from the frequency distribution of haemoglobin concentration of the total sample population. Methods Data collected by Lozoff et al. (1986) from 345 Costa Rican infants 12-23 months old were used to estimate the parameters of the IDA and NA ha emoglobin distributions determined by MDA and the widely used three-criteri a model of iron deficiency. The estimates of the prevalence of IDA by each of the methods were compared. The sensitivity and specificity of MDA compar ed to diagnosis by the three-criteria method were assessed. Simulations wer e carried out to assess the comparability of MDA and the three-criteria met hod in low and high prevalence scenarios. Results The mean and standard deviation (SD) of the NA haemoglobin distribu tion determined by both methods was 12.1 +/- 1.0 g/dL. The IDA haemoglobin distribution determined by MDA had a mean and SD of 10.2 +/- 1.3 g/dL while the IDA distribution by the three-criteria method had a mean and SD of 10. 4 +/- 1.3 g/dL. The prevalences of IDA as estimated by MDA and the three-cr iteria method were 24% and 29%, respectively. The sensitivity and specifici ty of MDA were 95% and 97%, respectively. The performance of MDA was simila r to the three-criteria method at a simulated high prevalence of IDA and le ss similar at a low prevalence of IDA. Conclusions Compared to the reference three-criteria method MDA provides a more accurate estimate of the true prevalence of IDA than the haemoglobin c utoff method in a population of children aged 12-23 months with a moderate to high prevalence of IDA. MDA is a less costly method for estimating the s everity of IDA in populations with moderate to high prevalences of IDA, and for assisting in the design, monitoring and evaluation of iron interventio n programmes.