Screening for anemia in Red Cross blood donor clinics

Accurate screening for anemia at Red Cross blood donor clinics is essential to maintain a safe national blood supply. Despite the importance of identifying anemia correctly by measurement of hemoglobin or hematocrit (hemoglobin/hematocrit) there is no consensus regarding the efficacy of the current two stage screening method which uses the Readacrit$\sp{\rm tm}$ microhematocrit in conjunction with copper sulfate.^ A cross-sectional study was implemented in which hemoglobin/hematocrit was measured, with the present method and four new devices, on 504 prospective blood donors at a Canadian Red Cross permanent blood donor clinic in London, Canada. Concurrently gathered, venous and capillary blood samples were tested by each device and compared to Coulter S IV$\sp{\rm tm}$ determined venous standard readings. Instrument hemoglobin/hematocrit means were statistically calibrated to the standard ones in order to appraise systematic deviations from the standard. Classification analysis was employed to assess concordance between each instrument and the standard when classifying prospective donors as anemic or non-anemic. This was done both when each instrument was used alone (single stage) and when copper sulfate was used as a preliminary screen (two stage) and simulated over a range of anemia prevalences. The Hemoximeter$\sp{\rm tm}$ and Compur M1000$\sp{\rm tm}$ devices had the highest correlations of hemoglobin measurements with the standard ones for both capillary (n.s.) and venous blood (p $<$.05). Analysis of variance (anova) also showed them to be the most accurate (p $<$.05), as did both single and two stage classification analysis, therefore, they are both recommended. There was a smaller difference between instruments for two stage than for single stage screening; therefore instrument choice is less crucial for the former. The present method was adequate for two stage screening as tested but simulations showed that it would discriminate poorly in populations with a higher prevalence of anemia. The Stat-crit and Readacrit, which measure hematocrit, became less accurate at crucial low hematocrit levels. In light of this finding and the introduction of new, effective and easy to use hemoglobin measuring instruments, the continued use of hematocrit as a surrogate for hemoglobin, is not recommended. ^

A STUDY TO INVESTIGATE DIET DIVERSITY AS A NUTRITION ASSESSMENT INSTRUMENT

Nutrient intake and specific food item data from 24-hour dietary recalls were utilized to study the relationship between measures of diet diversity and dietary adequacy in a population of white females of child-bearing age and socioeconomic subgroups of that population. As the basis of the diet diversity measures, twelve food groups were constructed from the 24-hour recall data and the number of unique foods per food group counted and weighted according to specified weighting schemes. Utilizing these food groups, nine diet diversity indices were developed.^ Sensitivity/specificity analysis was used to determine the ability of varying levels of selected diet diversity indices to identify individuals above and below preselected intakes of different nutrients. The true prevalence proportions, sensitivity and specificity, false positive and false negative rates, and positive predictive values observed at the selected levels of diet diversity indices were investigated in relation to the objectives and resources of a variety of nutrition improvement programs. Diet diversity indices constructed from the total population data were evaluated as screening tools for respondent nutrient intakes in each of the socioeconomic subgroups as well.^ The results of the sensitivity/specificity analysis demonstrated that the false positive rate, the false negative rate, or both were too high at each diversity cut-off level to validate the widespread use of any of the diversity indices in the dietary assessment of the study population. Although diet diversity has been shown to be highly correlated with the intakes of a number of nutrients, the diet diversity indices constructed in this study did not adequately represent nutrient intakes in the diet as reported, in this study, intakes as reported in the 24-hour dietary recall. Specific cut-off levels of selected diversity indices might have limited application in some nutrition programs. The results were applicable to the sensitivity/specificity analyses in the socioeconomic subgroups as well as in the total population. ^