Fresh capillary blood analysis using darkfield microscopy as a tool for screening nutritional deficiencies of iron and cobalamin (vitamin B12): A validity study

Objectives: The practice of fresh capillary blood analysis using darkfield microscopy (FCB-DM), commonly termed ‘live blood analysis’, is currently used as a point of care screening tool for several health aberrations, including nutritional deficiencies. There is currently a paucity of scientific research into the use of this technique and there is no research to date investigating the use of FCB-DM as a screening tool for nutritional deficiencies. The purpose of this study was to begin the process of validating this technique in screening for nutritional deficiencies of iron and cobalamin. Methods: FCB-DM screenings were performed on 29 consenting participants who were likely to be deficient in iron or cobalamin. The FCB-DM screenings were photographed to permit a quantitative analysis of cell size and morphology. Each participant provided a sample of venous blood soon after the FCB-DM screening for diagnostic pathology testing. The researcher was blinded to the pathology results until all FCB-DM data analysis was complete. Data from the FCB-DM screenings were correlated with the results of pathology blood tests used for the diagnosis of iron and cobalamin deficiencies. The sensitivity and specificity of FCB-DM parameters for detecting low iron or cobalamin levels were calculated. Results: Significant correlations were found between serum ferritin and the FCB-DM parameters of annulocytosis, elliptocytosis and microcytosis. Elliptocytosis showed the best performance for test sensitivity and specificity for low iron levels. The FCB-DM parameters of macrocytosis and anisocytosis showed significant correlations with pathology methylmalonic acid, homocysteine and holotranscobalamin II. Anisocytosis was found to have good test sensitivity and specificity for low cobalamin levels. Conclusion: These findings suggest that the FCB-DM parameter elliptocytosis is a valid marker of low iron levels and that anisocytosis is a valid marker of low cobalamin levels. However further research into all FCB-DM parameters is required to validate their use.