A novel method for quantification of human hemoglobin from dried blood spots by use of tandem mass spectrometry

A reliable and high throughput HPLC-HRMS method for the rapid screening of β-thalassemia and hemoglobinopathy in dried blood spots

OBJECTIVES

Traditional methods for β-thalassemia screening usually rely on the structural integrity of hemoglobin (Hb), which can be affected by the hemolysis of red blood cells and Hb degradation. Here, we aim to develop a reliable and high throughput method for rapid detection of β-thalassemia using dried blood spots (DBS).

METHODS

Hb components were extracted from a disc (3.2 mm diameter) punched from the DBS samples and digested by trypsin to produce a series of Hb-specific peptides. An analytical system combining high-resolution mass spectrometry and high-performance liquid chromatography was used for biomarker selection. The selected marker peptides were used to calculate delta/beta (δ/β) and beta-mutated/beta (β_M/β) globin ratios for disease evaluation.

RESULTS

Totally, 699 patients and 629 normal individuals, aged 3 days to 89 years, were recruited for method construction. Method assessment showed both the inter-assay and intra-assay relative standard deviation values were less than 10.8%, and the limits of quantitation for the proteo-specific peptides were quite low (1.0-5.0 μg/L). No appreciable matrix effects or carryover rates were observed. The extraction recoveries ranged from 93.8 to 128.7%, and the method was shown to be stable even when the samples were stored for 24 days. Prospective applications of this method in 909 participants also indicated good performance with a sensitivity of 100% and a specificity of 99.6%.

CONCLUSIONS

We have developed a fast, high throughput and reliable method for screening of β-thalassemia and hemoglobinopathy in children and adults, which is expected to be used as a first-line screening assay.

Dried blood sample analysis by antibody array across the total testing process

Dried blood samples (DBSs) have many advantages; yet, impediments have limited the clinical utilization of DBSs. We developed a novel volumetric sampling device that collects a precise volume of blood, which overcomes the heterogeneity and hematocrit issues commonly encountered in a traditional DBS card collection as well as allowing for more efficient extraction and processing procedures and thus, more efficient quantitation, by using the entire sample. We also provided a thorough procedure validation using this volumetric DBS collection device with an established quantitative proteomics analysis method, and then analyzed 1000 proteins using this approach in DBSs concomitantly with serum for future consideration of utility in clinical applications. Our data provide a first step in the establishment of a DBS database for the broad application of this sample type for widespread use in clinical proteomic and other analyses applications.

Reproducibility and Validity of Capillary Dried Blood Spot for Diagnosis of Vitamin A Deficiency and Anemia in Children <5 Years Old

BACKGROUND

Vitamin A deficiency (VAD) and anemia are the most prevalent nutritional deficiency in children globally. The dried blood spot (DBS) method has been used in prevalence studies of VAD and anemia in different age groups. However, it has not yet been validated for children.

OBJECTIVES

This study aimed to assess the reproducibility and validity of DBS in the diagnosis of VAD and anemia in preschoolers.

METHODS

Venous and capillary blood samples were collected from a representative sample of children <5 y old who attended the public health system in Rio de Janeiro. Serum retinol and hemoglobin were measured in 235 and 182 children, respectively. Serum retinol was measured with HPLC and hemoglobin was measured with spectrophotometry in samples of venous (gold standard) and capillary blood (test method, DBS). DBS reproducibility was assessed with the intraclass correlation coefficient (ICC), κ, and prevalence-adjusted and bias-adjusted κ (PABAK). DBS validity was assessed with sensitivity, specificity, accuracy index (AI), positive predictive value (PPV), and negative predictive value (NPV).

RESULTS

DBS showed very good reproducibility for serum retinol (ICC = 0.94, κ = 0.83, PABAK = 0.76) and very good/good reproducibility for hemoglobin (ICC = 0.86, κ = 0.69, PABAK = 0.69). Prevalence rates for VAD by the reference and test methods were 11.5% and 11.9%, respectively, whereas the anemia rates were 19.2% and 46.2%. The test method showed low sensitivity (33%) and PPV (32%) and high specificity (91%) and NPV (92%) for serum retinol. For hemoglobin, the test method showed fair sensitivity (71%), low PPV (30%), fair specificity (60%), and high NPV (90%). AI was 83% for VAD and 62% for anemia.

CONCLUSIONS

The results suggest that DBS is adequate for the diagnosis of VAD in preschool children, but not for anemia.

Advances in mass spectrometric methods for detection of hemoglobin disorders

Hemoglobin disorders are caused due to alterations in the hemoglobin molecules. These disorders are categorized in two broad classes - hemoglobin variants and thalassemias. The hemoglobin variants arise due to point mutations in the alpha (α), beta (β), gamma (γ), delta (δ), or epsilon (ε) globin chains of these proteins, while thalassemias are caused due to the under-production of α or β globin chain. Hemoglobin disorders account for 7 % of the major health issues globally. Mass Spectrometry is an extensively used analytical tool in the field of protein identification, protein-protein interaction, biomarker discovery and diagnosis of several impairments including hemoglobin related disorders. The remarkable advancements in the technology and method development have enormously augmented the clinical significance of mass spectrometry in these fields. The present review describes hemoglobin disorders and the recent advancements in mass spectrometry in the detection of such disorders, including its advantages, lacunae, and future directions. The literature evidence concludes that mass spectrometry can be potentially used as a 'First Line Screening Assay' for the detection of hemoglobin disorders in the near future.

Automation of RNA-based biomarker extraction from dried blood spots for the detection of blood doping

Aim: Transcriptomic biomarkers originating from reticulocytes measured in dried blood spots (DBSs) may be reliable indicators of blood doping. Methods/results: Here, we examined changes in the expression levels of the erythropoiesis-related ALAS2, CA1 and SLC4A1 genes in DBS samples from elite athletes and volunteers of clinical study with recombinant erythropoietin dose. Conclusion: By comparing the mean intraday coefficients of variation for ALAS2L, ALASLC, CA1 and SLC4A1 between manual and automated RNA extractions, an average improvement was observed, whereas the assessment of interday variability provided comparable results for both manual and automated approaches. Our results confirmed that RNA biomarkers on DBS support are efficient to detect blood doping.

A Novel, Nondestructive, Dried Blood Spot-Based Hematocrit Prediction Method Using Noncontact Diffuse Reflectance Spectroscopy

Dried blood spot (DBS) sampling is recognized as a valuable alternative sampling strategy both in research and in clinical routine. Although many advantages are associated with DBS sampling, its more widespread use is hampered by several issues, of which the hematocrit effect on DBS-based quantitation remains undoubtedly the most widely discussed one. Previously, we developed a method to derive the approximate hematocrit from a nonvolumetrically applied DBS based on its potassium content. Although this method yielded good results and was straightforward to perform, it was also destructive and required sample preparation. Therefore, we now developed a nondestructive method which allows to predict the hematocrit of a DBS based on its hemoglobin content, measured via noncontact diffuse reflectance spectroscopy. The developed method was thoroughly validated. A linear calibration curve was established after log/log transformation. The bias, intraday and interday imprecision of quality controls at three hematocrit levels and at the lower and upper limit of quantitation (0.20 and 0.67, respectively) were less than 11%. In addition, the influence of storage and the volume spotted was evaluated, as well as DBS homogeneity. Application of the method to venous DBSs prepared from whole blood patient samples (n = 233) revealed a good correlation between the actual and the predicted hematocrit. Limits of agreement obtained after Bland and Altman analysis were -0.076 and +0.018. Incurred sample reanalysis demonstrated good method reproducibility. In conclusion, mere scanning of a DBS suffices to derive its approximate hematocrit, one of the most important variables in DBS analysis.