The Accuracy of Dried Blood Spots Compared to Plasma or Serum Retinol for the Diagnosis of Vitamin A Deficiency: A DTA Systematic Review and Meta-Analysis

Abstract

Abstract Objectives Dried blood spots (DBS) do not require a cold chain, making them easier to store and transport compared to serum or plasma samples in resource-limited settings. Our objective was to determine the accuracy of DBS compared to serum or plasma retinol for assessing vitamin A status in individuals and populations. Methods A systematic review of diagnostic test accuracy (DTA) was performed using standard Cochrane Methods for Screening and Diagnostic Tests. All human studies were included if they determined retinol in DBS (index test) and compared results to retinol determined in either plasma or serum samples (reference standard). Index and reference methods could use either capillary or venous blood with retinol quantified by HPLC. We used the WHO threshold of 0.70 μmol/L to define low retinol concentrations. Meta-analysis determined summary estimates of sensitivity and specificity using the bivariate model, which models logit transformed sensitivities and specificities as a bivariate normal distribution including a parameter for the negative correlation between sensitivity and specificity. Rstudio (Version 1.1.456, RStudio, Inc. Boston, MA) was used for analysis. Results Our search (conducted April 10, 2019) identified 9021 records, and 285 studies were assessed in full-text for inclusion; 6 publications reported 8 studies comprising 397 participants, 50 of which had low serum retinol by the reference method. The use of DBS to determine a low retinol level had summary estimates (95% CIs) for sensitivity of 86.7% (71.4 to 94.5) and specificity of 99.5% (89.7 to 100.0). Conclusions Use of DBS to determine low retinol has been shown to have good sensitivity and high specificity compared to serum or plasma. Use of DBS can reduce the need for centrifugation and cold chain for storage and transport. The mixed use of capillary and venous blood in both index and reference methods merits further investigation for the determination of retinol in DBS. Funding Sources None declared.