A highly accurate mass spectrometry method for the quantification of phenylalanine and tyrosine on dried blood spots: Combination of liquid chromatography, phenylalanine/tyrosine-free blood calibrators and multi-point/dynamic calibration

BACKGROUND

Measurement of quantitative levels of phenylalanine and tyrosine in blood is an essential test for the diagnosis of and monitoring genetic disorders associated with phenylalanine metabolism, such as phenylketonuria (PKU), tyrosinemia, and defects of tetrahydrobiopterin synthesis and recycling. We developed a highly accurate and fast liquid chromatography with tandem mass spectrometry (LC-MS/MS) method for the quantification of phenylalanine and tyrosine on dried blood spot (DBS). We also designed a performance score system to evaluate various calibration methods in matrix matched material.

METHODS

Phenylalanine/tyrosine-free whole blood was used to make accurate and stable DBS calibrators. Six calibrators cover the range of 0-1000 µmol/L. Underivatized phenylalanine and tyrosine were extracted and measured by LC-MS/MS. Precision, accuracy, limit of quantification, recovery and carryover were validated. External quality assurance materials were also used to evaluate performance of multi-point calibrations and single-point calibrations.

RESULTS

The run time was 4.5-minute. Accuracy analysis showed good agreement with reference materials. Precision, recovery, and the lower and upper limit of quantification met the criteria. When phenylalanine and tyrosine concentrations were less than 150 µmol/L, the 5-point calibration without the calibrator of 1000 µmol/L had the best performance. When the concentrations were > 250 µmol/L, the single-point calibration of 500 µmol/L had the best performance.

CONCLUSION

We developed a simple, fast and highly accurate method for the detection of phenylalanine and tyrosine on DBS, with chromatographic separation and underivatized analysis. Based on the calibration performance, a 6-point calibration method is satisfying for this test. An optional dynamic calibration method, which includes 6-point calibration, 5-point calibration and single-point calibration, can further increase test reliability.

Volumetric absorptive microsampling: its use in COVID-19 research and testing

COVID-19 led to changes in the way blood samples are collected. As societies were isolated to control viral spread, access to facilities became limited. Remote sample collection with a volumetric microsampling approach, using Mitra® devices based on VAMS® technology, proved to be highly effective. It allowed people to collect high-quality samples at home and post them to a laboratory. This enabled scientists to conduct large serosurveillance studies, with results showing that seroprevalence of COVID-19 was higher than initially expected. Furthermore, remote microsampling studies by several institutions were conducted to measure the relationship between antigen levels and antibody response and duration. VAMS technology was also used in COVID-19 clinical trials. In summary, the independent research reviewed in this paper proved that VAMS is an effective sample collection alternative.

Comparison of Dried Blood Spots and Venous Blood for the Detection of SARS-CoV-2 Antibodies in a Population of Nursing Home Residents

In the current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, testing for SARS-CoV-2-specific antibodies is paramount for monitoring immune responses in postauthorization vaccination and seroepidemiological studies. However, large-scale and iterative serological testing by venipuncture in older persons can be challenging. Capillary blood sampling using a finger prick and collection on protein saver cards, i.e., dried blood spots (DBSs), has already proven to be a promising alternative. However, elderly persons have reduced cutaneous microvasculature, which may affect DBS-based antibody testing. Therefore, we aimed to evaluate the performance of DBS tests for the detection of SARS-CoV-2 antibodies among nursing homes residents. We collected paired venous blood and DBS samples on two types of protein saver cards (Whatman and EUROIMMUN) from nursing home residents, as well as from staff members as a reference population. Venous blood samples were analyzed for the presence of SARS-CoV-2 IgG antibodies using the Abbott chemiluminescent microparticle immunoassay (CMIA). DBS samples were analyzed by the EUROIMMUN enzyme-linked immunosorbent assay (ELISA) for SARS-CoV-2 IgG antibodies. We performed a statistical assessment to optimize the ELISA cutoff value for the DBS testing using Youden's J index. A total of 273 paired DBS-serum samples were analyzed, of which 129 were positive, as assessed by the reference test. The sensitivities and specificities of DBS testing ranged from 95.0% to 97.1% and from 97.1% to 98.8%, respectively, depending on the population (residents or staff members) and the DBS card type. Therefore, we found that DBS sampling is a valid alternative to venipuncture for the detection of SARS-CoV-2 antibodies among elderly subjects. IMPORTANCE Since the implementation of newly developed SARS-CoV-2 vaccines in the general population, serological tests are of increasing importance. Because DBS samples can be obtained with a finger prick and can be shipped and stored at room temperature, they are optimal for use in large-scale SARS-CoV-2 serosurveillance or postauthorization vaccination studies, even in an elderly study population.

SARS-CoV-2 Antibody Binding and Neutralization in Dried Blood Spot Eluates and Paired Plasma

Wide-scale assessment of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific antibodies is critical to understanding population seroprevalence, correlates of protection, and the longevity of vaccine-elicited responses. Most SARS-CoV-2 studies characterize antibody responses in plasma/sera. While reliable and broadly used, these samples pose several logistical restrictions, such as requiring venipuncture for collection and a cold chain for transportation and storage. Dried blood spots (DBS) overcome these barriers as they can be self-collected by fingerstick and mailed and stored at ambient temperature. Here, we evaluate the suitability of DBS for SARS-CoV-2 antibody assays by comparing several antibody responses between paired plasma and DBS from SARS-CoV-2 convalescent and vaccinated individuals. We found that DBS not only reflected plasma antibody binding by enzyme-linked immunosorbent assay (ELISA) and epitope profiles using phage display, but also yielded SARS-CoV-2 neutralization titers that highly correlated with paired plasma. Neutralization measurement was further streamlined by adapting assays to a high-throughput 384-well format. This study supports the adoption of DBS for numerous SARS-CoV-2 binding and neutralization assays. IMPORTANCE Plasma and sera isolated from venous blood represent conventional sample types used for the evaluation of SARS-CoV-2 antibody responses after infection or vaccination. However, collection of these samples is invasive and requires trained personnel and equipment for immediate processing. Once collected, plasma and sera must be stored and shipped at cold temperatures. To define the risk of emerging SARS-CoV-2 variants and the longevity of immune responses to natural infection and vaccination, it will be necessary to measure various antibody features in populations around the world, including in resource-limited areas. A sampling method that is compatible with these settings and is suitable for a variety of SARS-CoV-2 antibody assays is therefore needed to continue to understand and curb the COVID-19 pandemic.

Development of a Quantitative FMRP Assay for Mouse Tissue Applications

Fragile X syndrome results from the absence of the FMR1 gene product—Fragile X Mental Retardation Protein (FMRP). Fragile X animal research has lacked a reliable method to quantify FMRP. We report the development of an array of FMRP-specific monoclonal antibodies and their application for quantitative assessment of FMRP (qFMRPm) in mouse tissue. To characterize the assay, we determined the normal variability of FMRP expression in four brain structures of six different mouse strains at seven weeks of age. There was a hierarchy of FMRP expression: neocortex > hippocampus > cerebellum > brainstem. The expression of FMRP was highest and least variable in the neocortex, whereas it was most variable in the hippocampus. Male C57Bl/6J and FVB mice were selected to determine FMRP developmental differences in the brain at 3, 7, 10, and 14 weeks of age. We examined the four structures and found a developmental decline in FMRP expression with age, except for the brainstem where it remained stable. qFMRPm assay of blood had highest values in 3 week old animals and dropped by 2.5-fold with age. Sex differences were not significant. The results establish qFMRPm as a valuable tool due to its ease of methodology, cost effectiveness, and accuracy.

Cell Analysis from Dried Blood Spots: New Opportunities in Immunology, Hematology, and Infectious Diseases

Blood cell analysis is a major pillar of biomedical research and healthcare. These analyses are performed in central laboratories. Rapid shipment from collection site to the central laboratories is currently needed because cells and biomarkers degrade rapidly. The dried blood spot from a fingerstick allows the preservation of cellular molecules for months but entire cells are never recovered. Here leucocyte elution is optimized from dried blood spots. Flow cytometry and mRNA expression profiling are used to analyze the recovered cells. 50-70% of the leucocytes that are dried on a polyester solid support via elution after shaking the support with buffer are recovered. While red blood cells lyse upon drying, it is found that the majority of leucocytes are preserved. Leucocytes have an altered structure that is improved by adding fixative in the elution buffer. Leucocytes are permeabilized, allowing an easy staining of all cellular compartments. Common immunophenotyping and mRNAs are preserved. The ability of a new biomarker (CD169) to discriminate between patients with and without Severe Acute Respiratory Syndrome induced by Coronavirus 2 (SARS-CoV-2) infections is also preserved. Leucocytes from blood can be dried, shipped, and/or stored for at least 1 month, then recovered for a wide variety of analyses, potentially facilitating biomedical applications worldwide.

Prospective identification by neonatal screening of patients with guanidinoacetate methyltransferase deficiency

INTRODUCTION

Guanidinoacetate methyltransferase (GAMT) deficiency is an inherited metabolic disorder that impairs the synthesis of creatine (CRE). Lack of CRE in the brain can cause intellectual disability, autistic-like behavior, seizures, and movement disorders. Identification at birth and immediate therapy can prevent intellectual disability and seizures. Here we report the first two cases of GAMT deficiency identified at birth by newborn screening (NBS) in Utah and New York.

METHODS

NBS dried blood spots were analyzed by tandem mass spectrometry (MS/MS) using either derivatized or non-derivatized assays to detect guanidinoacetate (GUAC) and CRE. For any positive samples, a second-tier test using a more selective method, ultra-performance liquid chromatography (UPLC) combined with MS/MS, was performed to separate GUAC from potential isobaric interferences.

RESULTS

NBS for GAMT deficiency began in Utah on June 1, 2015 using a derivatized method for the detection of GUAC and CRE. In May 2019, the laboratory and method transitioned to a non-derivatized method. GAMT screening was added to the New York State NBS panel on October 1, 2018 using a derivatized method. In New York, a total of 537,408 babies were screened, 23 infants were referred and one newborn was identified with GAMT deficiency. In Utah, a total of 273,902 infants were screened (195,425 with the derivatized method, 78,477 with the non-derivatized method), three infants referred and one was identified with GAMT deficiency. Mean levels of GUAC and CRE were similar between methods (Utah derivatized: GUAC = 1.20 ± 0.43 μmol/L, CRE = 238 ± 96 μmol/L; Utah non-derivatized: GUAC = 1.23 ± 0.61 μmol/L, CRE = 344 ± 150 μmol/L, New York derivatized: GUAC = 1.34 ± 0.57 μmol/L, CRE = 569 ± 155 μmol/L). With either Utah method, similar concentrations of GUAC are observed in first (collected around 1 day of age) and the second NBS specimens (routinely collected at 7-16 days of age), while CRE concentrations decreased in the second NBS specimens. Both infants identified with GAMT deficiency started therapy by 2 weeks of age and are growing and developing normally at 7 (Utah) and 4 (New York) months of age.

CONCLUSIONS

Newborn screening allows for the prospective identification of GAMT deficiency utilizing elevated GUAC concentration as a marker. First-tier screening may be incorporated into existing methods for amino acids and acylcarnitines without the need for new equipment or staff. Newborn screening performed by either derivatized or non-derivatized methods and coupled with second-tier testing, has a very low false positive rate and can prospectively identify affected children. SummaryCerebral creatine deficiency syndromes caused by defects in creatine synthesis can result in intellectual disability, and are preventable if therapy is initiated early in life. This manuscript reports the identification of two infants with GAMT deficiency (one of the cerebral creatine deficiency syndromes) by newborn screening and demonstrates NBS feasibility using a variety of methods.

Coming up short: Comparing venous blood, dried blood spots & saliva samples for measuring telomere length in health equity research

BACKGROUND

Telomere length (TL) in peripheral blood mononuclear cells (PBMC) from fresh venous blood is increasingly used to estimate molecular impacts of accumulated social adversity on population health. Sometimes, TL extracted from saliva or dried blood spots (DBS) are substituted as less invasive and more scalable specimen collection methods; yet, are they interchangeable with fresh blood? Studies find TL is correlated across tissues, but have not addressed the critical question for social epidemiological applications: Do different specimen types show the same association between TL and social constructs?

METHODS

We integrate expertise in social epidemiology, molecular biology, and the statistical impact of measurement error on parameter estimates. Recruiting a diverse sample of 132 Metro-Detroit women, we measure TL for each woman from fresh blood PBMC, DBS, and saliva. Using regression methods, we estimate associations between social characteristics and TL, comparing estimates across specimen types for each woman.

RESULTS

Associations between TL and social characteristics vary by specimen type collected from the same woman, sometimes qualitatively altering estimates of the magnitude or direction of a theorized relationship. Being Black is associated with shorter TL in PBMC, but longer TL in saliva or DBS. Education is positively associated with TL in fresh blood, but negatively associated with TL using DBS.

CONCLUSION

Findings raise concerns about the use of TL measures derived from different tissues in social epidemiological research. Investigators need to consider the possibility that associations between social variables and TL may be systematically related to specimen type, rather than be valid indicators of socially-patterned biopsychosocial processes.

No pain, just gain: Painless, easy, and fast dried blood spot collection from fingertip and upper arm in doping control

This study aimed to determine and compare the perception, painfulness, and usability of the minimally invasive dried blood spot (DBS) collections from fingertip versus upper arm from different athlete populations: males and females representing sports dependent on hand/arm, sports less dependent on hand/arm and para-athletes. To accomplish this, 108 national level athletes from Denmark were recruited (♀ = 49, ♂ = 59, 25 ± 6 years; mean ± SD) and 11 Doping Control Officers (DCOs) collected manual fingerprick DBS (HemaSpot HF) and automated upper-arm DBS (Tasso-M20) from each athlete. Athletes and DCOs responded to questionnaires regarding the perception of sample collection procedures. On a 0-10 scale, the athletes reported a low pain score and a very good general experience for both sampling sites, but following upper-arm DBS collection, the associated pain was rated lower (-0.4 ± 1.6, p < 0.05), and the general experience rated better (+0.6 ± 2.3, p ≤ 0.001) than after the fingerprick DBS collection. The DCOs rated the general experience with the upper-arm DBS collection better (+1.6 ± 1.1, p ≤ 0.01) than the fingerprick DBS collection, partly because problems occurred more frequently during the DBS collection from the fingertip (28%) than from the upper arm (6%). In conclusion, it appears that DBS sampling is affiliated with minimal sensation of pain and is preferred by both DCOs and athletes, independent of gender and discipline, over conventional sample collection methods. Collection of DBS from the upper arm was preferred over fingerprick by both athletes and DCOs.

Validation of high-throughput, semiquantitative solid-phase SARS coronavirus-2 serology assays in serum and dried blood spot matrices

Aim: Serological assays for the detection of anti-SARS coronavirus-2 (SARS-CoV-2) antibodies are essential to the response to the global pandemic. A ligand binding-based serological assay was validated for the semiquantitative detection of IgG, IgM, IgA and neutralizing antibodies (nAb) against SARS-CoV-2 in serum. Results: The assay demonstrated high levels of diagnostic specificity and sensitivity (85-99% for all analytes). Serum IgG, IgM, IgA and nAb correlated positively (R2 = 0.937, R2 = 0.839, R2 = 0.939 and R2 = 0.501, p < 0.001, respectively) with those measured in dried blood spot samples collected using the hemaPEN® microsampling device (Trajan Scientific and Medical, Victoria, Australia). In vitro SARS-CoV-2 pseudotype neutralization correlated positively with the solid phase nAb signals in convalescent donors (R2 = 0.458, p < 0.05). Conclusion: The assay is applicable in efficacy studies, infection monitoring and postmarketing surveillance following vaccine rollout.

A dried blood spot protocol for high throughput analysis of SARS-CoV-2 serology based on the Roche Elecsys anti-N assay

BACKGROUND

Since 2020 SARS-CoV-2 spreads pandemically, infecting more than 119 million people, causing >2·6 million fatalities. Symptoms of SARS-CoV-2 infection vary greatly, ranging from asymptomatic to fatal. Different populations react differently to the disease, making it very hard to track the spread of the infection in a population. Measuring specific anti-SARS-CoV-2 antibodies is an important tool to assess the spread of the infection or successful vaccinations. To achieve sufficient sample numbers, alternatives to venous blood sampling are needed not requiring medical personnel or cold-chains. Dried-blood-spots (DBS) on filter-cards have been used for different studies, but not routinely for serology.

METHODS

We developed a semi-automated protocol using self-sampled DBS for SARS-CoV-2 serology. It was validated in a cohort of matched DBS and venous-blood samples (n = 1710). Feasibility is demonstrated with two large serosurveys with 10247 company employees and a population cohort of 4465 participants.

FINDINGS

Sensitivity and specificity reached 99·20% and 98·65%, respectively. Providing written instructions and video tutorials, 99·87% (4465/4471) of the unsupervised home sampling DBS cards could be analysed.

INTERPRETATION

DBS-sampling is a valid and highly reliable tool for large scale serosurveys. We demonstrate feasibility and accuracy with a large validation cohort including unsupervised home sampling. This protocol might be of big importance for surveillance in resource-limited settings, providing low-cost highly accurate serology data.

FUNDING

Provided by Bavarian State Ministry of Science and the Arts, LMU University-Hospital; Helmholtz-Centre-Munich, German Ministry for Education and Research (project01KI20271); University of Bonn; University of Bielefeld; the Medical Biodefense Research Program of Bundeswehr-Medical-Service; Euroimmun, RocheDiagnostics provided discounted kits and machines.

Profiling of intact blood proteins by matrix-assisted laser desorption/ionization mass spectrometry without the need for freezing - Dried serum spots as future clinical tools for patient screening

RATIONALE

To open up new ways for matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS)-based patient screening, blood serum is the most preferred specimen because of its richness in patho-physiological information and due to ease of collection. To overcome deleterious freeze/thaw cycles and to reduce high costs for shipping and storage, we sought to develop a procedure which enables MALDI-MS protein profiling of blood serum proteins without the need for serum freezing.

METHODS

Blood sera from patients/donors were divided into portions which after pre-incubation were fast frozen. Thawed aliquots were deposited on filter paper discs and air-dried at room temperature. Intact serum proteins were eluted with acid-labile detergent-containing solutions and were desalted by employing a reversed-phase bead system. Purified protein solutions were screened by MALDI-MS using standardized instrument settings.

RESULTS

MALDI mass spectra from protein solutions which were eluted from filter paper discs and desalted showed on average 25 strong ion signals (mass range m/z 6000 to 10,000) from intact serum proteins (apolipoproteins, complement proteins, transthyretin and hemoglobin) and from proteolytic processing products. Semi-quantitative analysis of three ion pairs: m/z 6433 and 6631, m/z 8205 and 8916, as well as m/z 9275 and 9422, indicated that the mass spectra from either pre-incubated fast-frozen serum or pre-incubated dried serum spot eluted serum contained the same information on protein composition.

CONCLUSIONS

A workflow that avoids the conventional cold-chain and yet enables the investigation of intact serum proteins and/or serum proteolysis products by MALDI-MS profiling was developed. The presented protocol tremendously broadens the clinical application of MALDI-MS and simultaneously allows a reduction in the costs for storage and shipping of serum samples. This will pave the way for clinical screening of patients also in areas with limited access to health care systems, and/or specialized laboratories.

Pandemic-Associated Trends in Measurement of HbA1c in Children with Diabetes Mellitus and Validation of Dried Blood Spot as an Alternative Sample Matrix

OBJECTIVE

Routine monitoring of hemoglobin A1c (HbA1c) is the standard of care in diabetes mellitus (DM), but adhering to regular laboratory appointments may be challenging when access to care is limited, such as during the initial wave of the COVID-19 pandemic in the United States in 2020.

MATERIALS

We evaluated trends in patient encounters and laboratory testing for DM in a pediatric healthcare system from March to September 2019 and during the same period in 2020.

RESULTS

Evaluation of 17,367 patient encounters illustrated that the pandemic was associated with significantly fewer in-person office visits and point-of-care HbA1c tests for patients with DM in 2020 relative to 2019. A separate analysis of 7,193 HbA1c results measured by point-of-care testing in the general population found a significant increase in the number of measured HbA1c >14 % in May 2020 relative to 2019, but other measured HbA1c values did not differ. As a means to address lapses in the monitoring of HbA1c due to the pandemic, we evaluated the use of the dried blood spot (DBS) matrix for measurement of HbA1c by the Vitros 5600 chemistry analyzer. DBS HbA1c was well correlated to whole blood (r=0.9889) and exhibited intra- and inter-assay precision from 0.5-3.5%.

CONCLUSION

DBS measurement of HbA1c presents a viable alternative to routine in-person laboratory monitoring of DM.

Enantiomeric methadone quantitation on real post-mortem dried matrix spots samples: Comparison of liquid chromatography and supercritical fluid chromatography coupled to mass spectrometry

This study describes two bioanalytical methods for the quantitation of the two methadone enantiomers in dried matrix spots using high performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) and high performance supercritical chromatography tandem mass spectrometry (HPSFC-MS/MS). Dried matrix spots were obtained by spotting 10 µL of each sample fluid on a Whatman paper. Methadone and its main metabolite, EDDP, were extracted with 100 µL methanol and subsequently injected into the LC-MS/MS and SFC-MS/MS systems. Enantiomeric separation was achieved with AGP-column for the LC conditions and with Chiralpak IH-3 in SFC. The two methods were fully validated and 93 post-mortem samples were analysed with both analytical methods. Results from validation parameters and results obtained for all post-mortem samples were compared with a significant spearman correlation of r_s = 0.9978 for R-methadone and r_s = 0.9981 for S-methadone. The LC method provided better results in terms of uncertainty, retention factor and resolution, whereas SFC provides better sensitivity, with lower LOD. Median R-/S-methadone ratio in peripheral blood was found equal to 1.60 (N = 32), varying from 0.79 to 4.23. The reported values were in good agreement with previously published results. Based on the results obtained here, SFC-MS/MS can be considered a reliable alternative to the widely used LC-MS/MS for the quantitation of methadone enantiomers in bioanalysis and should be evaluated for other bioanalytical methods. Both methods can be easily and quickly used in toxicological routine analysis for the methadone quantitation in human fluids matrices, even if considering that the polysaccharide coated column IH-3 used in SFC does not allow the enantiomeric EDDP separation.

Newborn Screening for Fabry Disease in Northeastern Italy: Results of Five Years of Experience

Fabry disease (FD) is a progressive multisystemic lysosomal storage disease. Early diagnosis by newborn screening (NBS) may allow for timely treatment, thus preventing future irreversible organ damage. We present the results of 5.5 years of NBS for FD by α-galactosidase A activity and globotriaosylsphingosine (lyso-Gb₃) assays in dried blood spot through a multiplexed MS/MS assay. Furthermore, we report our experience with long-term follow-up of positive subjects. We screened more than 170,000 newborns and 22 males were confirmed to have a GLA gene variant, with an incidence of 1:7879 newborns. All patients were diagnosed with a variant previously associated with the later-onset phenotype of FD or carried an unclassified variant (four patients) or the likely benign p.Ala143Thr variant. All were asymptomatic at the last visit. Although lyso-Gb₃ is not considered a reliable second tier test for newborn screening, it can simplify the screening algorithm when its levels are elevated at birth. After birth, plasma lyso-Gb₃ is a useful marker for non-invasive monitoring of all positive patients. Our study is the largest reported to date in Europe, and presents data from long-term NBS for FD that reveals the current incidence of FD in northeastern Italy. Our follow-up data describe the early disease course and the trend of plasma lyso-Gb₃ during early childhood.

Real-world application of the Xpert® HBV viral load assay on serum and dried blood spots

As we strive towards the WHO goal of elimination of viral hepatitis as a public health threat by 2030, implementation of reliable, accurate diagnostic assays is crucial to identify those at risk of disease progression and those at risk of transmission. Ironically those at greatest risk of chronic hepatitis B are often in resource-poor regions with limited access to testing, collection, storage, and/or transportation of peripheral blood. The Xpert® HBV Viral Load assay provides an easy to use, convenient means of measuring load on GeneXpert platforms. In this study, the Xpert assay is evaluated against four commercially available high-throughput assays for Hepatitis B virus (HBV) loads. In addition application of dried blood spots (DBS) for estimation of viral load is assessed on real-world samples collected from a remote Pacific Island, Kiribati. A total of 107 serum/plasma samples were tested in the Xpert HBV load assay and compared with the Abbott m2000, Alinity m, and Roche Cobas CAP/CTM and 6800. Fifty-three DBS were tested in the Xpert assay and compared with matching serum samples. Overall 82% serum/plasma samples demonstrated good correlation between the Xpert and Roche and Abbott assays, to within 0.5 log10 IU/ml. The greatest discrepancies were seen at the limits of quantification of all assays. About 85.4% DBS gave estimable viral loads to within 1 log10 IU/ml of the serum load. The Xpert HBV viral load assay is recommended for all settings but particularly useful for resource-poor settings. Utility of DBS with the Xpert assay provides a simple means for testing in remote settings.

Adherence to cardiovascular pharmacotherapy by patients in Iraq: A mixed methods assessment using quantitative dried blood spot analysis and the 8-item Morisky Medication Adherence Scale

This study evaluated the adherence to prescribed cardiovascular therapy medications among cardiovascular disease patients attending clinics in Misan, Amara, Iraq. Mixed methods were used to assess medication adherence comprising the Arabic version of the eight-item Morisky Medication Adherence Scale (MMAS-8) and determination of drug concentrations in patient dried blood spot (DBS) samples by liquid chromatography-high resolution mass spectrometry. Three hundred and three Iraqi patients (median age 53 years, 50.5% female) who had been taking one or more of the nine commonly prescribed cardiovascular medications (amlodipine, atenolol, atorvastatin, bisoprolol, diltiazem, lisinopril, losartan, simvastatin and valsartan) for at least six months were enrolled. For each patient MMAS-8 scores were determined alongside drug concentrations in their dried blood spot samples. Results from the standardized questionnaire showed that adherence was 81.8% in comparison with 50.8% obtained using the laboratory-based microsample analysis. The agreement between the indirect (MMAS-8) and direct (DBS analysis) assessment approaches to assessing medication adherence showed significantly poor agreement (kappa = 0.28, P = 0.001). The indirect and direct assessment approaches showed no significant correlation between nonadherence to prescribed cardiovascular pharmacotherapy and age and gender, but were significantly associated with the number of medications in the patient's treatment regimen (MMAS-8: Odds Ratio (OR) 1.947, 95% CI, P = 0.001; DBS analysis: OR 2.164, 95% CI, P = 0.001). The MMAS-8 results highlighted reasons for nonadherence to prescribed cardiovascular pharmacotherapy in this patient population whilst the objective DBS analysis approach gave valuable information about nonadherence to each medication in the patient's treatment regimen. DBS sampling, due its minimally invasive nature, convenience and ease of transport is a useful alternative matrix to monitor adherence objectively in Iraq to cardiovascular pharmacotherapy. This information combined with MMAS-8 can provide clinicians with an evidence-based novel approach to implement intervention strategies to optimise and personalise cardiovascular pharmacotherapy in the Iraqi population and thereby improve patient health outcomes.

Volumetric Absorptive Microsampling as an Alternative Tool for Biomonitoring of Multi-Mycotoxin Exposure in Resource-Limited Areas

Biomonitoring of biological samples arises as an effective tool to evaluate the exposure to mycotoxins in the population. Owing to the wide range of advantages, there is a growing interest in the use of non- and minimally invasive alternative sampling strategies, such as dried blood spot sampling or volumetric absorptive microsampling (VAMS). A VAMS-based multi-mycotoxin method was developed and validated for 24 different mycotoxins. Method validation was based on the Bioanalytical Method Validation Guideline of the Food and Drug Administration from the United States and for most of the studied mycotoxins, the results of the performance characteristics were in agreement with the criteria of the European Commission Decision 2002/657/EC. The recovery for the different mycotoxins was not haematocrit dependent and remained acceptable after storing the VAMS for 7 and 21 days at refrigeration temperature (4 °C) and room temperature, demonstrating that VAMS could be applied to assess mycotoxin exposure in blood in resource-limited areas, where there may be a delay between sampling and analysis. Finally, a comparison between VAMS and a procedure for liquid whole blood analysis, performed on 20 different blood samples, did not result in missed exposed cases for VAMS. Moreover, both methods detected similar levels of ochratoxin A, ochratoxin alpha, zearalenone and aflatoxin B1. Given all the benefits associated with VAMS and the developed method, VAMS sampling may serve as an alternative to conventional venous sampling to evaluate multiple mycotoxin exposure.

An Evaluation of a Fluorescence In Situ Hybridization Strategy Using Air-dried Blood and Bone-marrow Smears in the Risk Stratification of Pediatric B-Lineage Acute Lymphoblastic Leukemia in Resource-limited Settings

Cytogenetic abnormalities (CAs), one of the strongest influencers of therapeutic outcome in pediatric B-cell precursor acute lymphoblastic leukemia (BCP-ALL), can be identified by different techniques. Despite several technological advances, many centers with resource-limited settings continue to use either reverse-transcriptase polymerase chain reaction (RT-PCR) and/or fluorescence in situ hybridization (FISH) to identify prognostically relevant CAs. We evaluated a simple and cost-effective triple-probe FISH strategy on air-dried blood and bone-marrow smears and compared its performance with a multiplex RT-PCR-based approach in the prognostication of pediatric BCP-ALL patients. Three hundred twenty BCP-ALL patients were tested prospectively and in parallel by FISH on air-dried blood or bone-marrow smears and RT-PCR. The FISH strategy correctly diagnosed all genetic abnormalities identified by RT-PCR. Prognostically relevant genetic abnormalities were missed by RT-PCR in 24 (8.1%) patients. In another 20 children (6%), with samples inadequate for RT-PCR testing (dry taps or due to poor sample quality), a successful FISH testing could be performed on bone-marrow aspirate or trephine-imprint smears. In addition, FISH detected ploidy changes, which could be confirmed by FxCycle Violet-based flow-cytometry. FISH testing on air-dried smears identified more prognostically relevant CAs, provided information on the ploidy status, and could be successfully performed in children with difficulty in bone-marrow sampling.

Are all blood-based postal sampling kits the same? A comparative service evaluation of the performance of dried blood spot and mini tube sample collection systems for postal HIV and syphilis testing

OBJECTIVES

We comparatively evaluated two HIV and syphilis blood sampling kits (dried blood spot (DBS) and mini tube (MT)) as part of an online STI postal sampling service that included tests for chlamydia and gonorrhoea. We aimed to see how the blood collection systems compared regarding sample return rates and result rates. Additionally, we aimed to observe differences in false-positive results and describe a request-to-result ratio (RRR)-the required number of kit requests needed to obtain one successful result.

METHODS

We reviewed data from an online postal STI kit requesting service for a client transitioning from MT to DBS blood collection systems. We described service user baseline characteristics and compared kit requests, kit and blood sample return rates, and the successful resulting rates for HIV and syphilis for MT and DBS. Pearson's χ2 and Fisher's exact test were used to determine statistical differences, and statistical formulae were applied to produce CIs for differences in proportions.

RESULTS

5670 STI postal kit requests from a Midlands region were reviewed from 6 September 2016-2 January 2019 (1515 MT and 4155 DBS). Baseline characteristics between the two groups were comparable (68.0% female, 74.0% white British and 87.5% heterosexual, median age 26 years). Successful processing rates for DBS were 94.6% and 54.4% for MT (p<0.001) with a percentage difference of 40.2% (95% CI 36.9% to 43.4%). The RRR for MT was 2.9 cf. 1.6 for DBS. False-positive results for MT samples were 5.2% (HIV) and 0.4% (syphilis), and those for DBS were 0.4% (HIV) and 0.0% (syphilis).

CONCLUSIONS

This comparative analysis demonstrated the superior successful processing rates for postal DBS collection systems compared with MT. Reasons for this included insufficient volumes, high false-positive rates and degradation of blood quality in MT samples. A postal sampling service using DBS to screen for HIV, syphilis and other blood-borne viruses could be a viable alternative.

Exploration of an Efficient Simultaneous Molecular Detection Method of HIV, HCV, and Syphilis from a Single Dried Blood Spot

OBJECTIVE

The aim of the present study was to evaluate the performance of the simultaneous detection of HIV-1 RNA, HIV-1 DNA, and HCV RNA using one dried blood spot (DBS) as an alternative sample to plasma.

METHOD

A total of 571 paired DBS/plasma samples were collected from men who have sex with men (MSM) and injection drug users (IDUs), and serological and molecular assays were performed. Using plasma results as the reference standard, the performance of DBS tests for HIV-1 RNA, HIV-1 DNA, and HCV RNA was evaluated. Pearson's correlation coefficients and Bland-Altman analysis were performed to assess the correlation and concordance between DBS and plasma.

RESULTS

Among paired plasma/DBS samples with detectable HIV-1 RNA and HCV RNA, five samples (5/32) were not detectable in DBS, while measurable HIV-1 RNA levels were present in plasma (1.44 to 3.99 log ₁₀ copies/mL). There were two samples (2/94) with undetectable HCV RNA in DBS, while measurable HCV RNA levels were present in plasma (-5 to 5.99 log ₁₀ copies/mL). The correlation between HIV-1 RNA light chain variable region (VL) values obtained from plasma and DBS showed that r = 0.683 ( P < 0.01), n = 27 and r = 0.612 ( P < 0.01), n = 89 in HCV RNA. Bland-Altman analysis revealed that in HIV-1 RNA, the mean (± SD) difference between HIV-1 RNA in plasma and DBS was 1.00 ± 1.01 log ₁₀ copies/mL, and all samples were within ± 1.96 SD (-0.97 to 2.97 log ₁₀ copies/mL) for DBS. The mean difference (± SD) in HCV RNA was 0.15 ± 1.08 log ₁₀ copies/mL, and 94.38% (84/89) were within ± 1.96 SD (-1.96 to 2.67 log ₁₀ copies/mL). Overall, HIV-1 RNA and HCV RNA levels obtained from a DBS were lower than those obtained from plasma. HIV-1 DNA in a DBS showed concordant results with HIV-1 RNA in plasma. HIV-1 DNA RT-PCR using a DBS showed acceptable performance.

CONCLUSION

The performance of the simultaneous detection of HIV-1 RNA, HIV-1 DNA, and HCV RNA using one DBS was acceptable. DBS, as an alternative sample to plasma, may be a viable option for the simultaneous detection of HIV-1 RNA, HIV-1 DNA, and HCV RNA in resource-limited settings or for individuals living in areas that are difficult to access.

Therapeutic drug monitoring of valproic acid using a dried plasma spot sampling device

Valproic acid (VPA) dosing needs to be individualized for epilepsy patients through therapeutic drug monitoring (TDM). The patients must show up in the clinic at the therapeutic window time to venipuncture sample. Dried plasma spot (DPS) sampling is an alternative way to replace conventional venipuncture sampling. The aim of this study was to develop and validate a DPS-based liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to monitor VPA in a routine clinical laboratory setting. We compare the DPS with the wet plasma method of clinical samples by LC-MS/MS. The method was linear over the dynamic range of 10-200 μg/ml (covering entire therapeutic range) with a correlation coefficient r² ≥ 0.995. Both the DPS and wet plasma methods were fully validated for the accuracy, precision, recovery, and matrix effect. The analyte stability was examined under conditions mimicking the sample storage, transport, and analysis procedures. A clinical study with epilepsy patients receiving VPA (n = 35) showed that, after correction for hematocrit (HCT), plasma concentrations can be successfully calculated from the DPS quantification results. Passing-Bablok regression coefficients showed no proportional bias between estimated and measured plasma concentrations. Similar agreement was found by Bland-Altman plots. The dried sample could be mailed to the clinical lab to test by regular mail service. So DPS can be used for drug monitoring with self-sampling strategy at the patient's convenient time and place specially for ambulatory patients not attending a clinic.

Reliability of dried blood spot (DBS) cards in antibody measurement: A systematic review

Background

Increasingly, vaccine efficacy studies are being recommended in low-and-middle-income countries (LMIC), yet often facilities are unavailable to take and store infant blood samples correctly. Dried blood spots (DBS), are useful for collecting blood from infants for diagnostic purposes, especially in low-income settings, as the amount of blood required is miniscule and no refrigeration is required. Little is known about their utility for antibody studies in children. This systematic review aims to investigate the correlation of antibody concentrations against infectious diseases in DBS in comparison to serum or plasma samples that might inform their use in vaccine clinical trials.

Methods and findings

We searched MEDLINE, Embase and the Cochrane library for relevant studies between January 1990 to October 2020 with no language restriction, using PRISMA guidelines, investigating the correlation between antibody concentrations in DBS and serum or plasma samples, and the effect of storage temperature on DBS diagnostic performance.

We included 40 studies in this systematic review. The antibody concentration in DBS and serum/plasma samples reported a good pooled correlation, (r² = 0.86 (ranged 0.43 to 1.00)). Ten studies described a decline of antibody after 28 days at room temperature compared to optimal storage at -20°C, where antibodies were stable for up to 200 days. There were only five studies of anti-bacterial antibodies.

Conclusions

There is a good correlation between antibody concentrations in DBS and serum/plasma samples, supporting the wider use of DBS in vaccine and sero-epidemiological studies, but there is limited data on anti-bacterial antibodies. The correct storage of DBS is critical and may be a consideration for longer term storage.

Transferrin isoform analysis from dried blood spots and serum samples by gel isoelectric focusing for screening congenital disorders of glycosylation

Congenital disorders of glycosylation (CDG) are a growing, heterogeneous group of genetic disorders caused by a defect in the glycoprotein synthesis. The first and still widely used method for routine CDG screening was isoelectric focusing (IEF) of serum transferrin. Dried blood spot (DBS) testing is commonly used in newborn screening procedures to detect inborn errors of metabolism. The aim of this study was to demonstrate the reliability of the IEF method in DBS testing. Dried blood spot testing can help in the postmortem diagnosis of CDG disorders when other material is unavailable. The patterns and concentrations of transferrin isoforms in serum and DBS are comparable, and slight differences do not affect interpretation of results.

Validation of dried blood spot sampling for determining trophic positions of Arctic char using nitrogen stable isotope analyses of amino acids

RATIONALE

Dried blood spots (DBSs) are gaining popularity for biomarker analyses in ecological research due to their advantages for use in field-based research and in remote settings; however, many DBS biomarkers remain unvalidated. We validated the application of compound-specific stable nitrogen isotope analyses of amino acids (CSIA-AAs) to field-prepared DBSs for determining trophic positions of wild-caught Arctic char (Salvelinus alpinus).

METHODS

Whole blood and muscle from Arctic char were collected, and DBSs were created in the field. We measured the stable nitrogen isotope ratios (expressed as δ¹⁵ N values) of the amino acids glutamic acid (Glu) and phenylalanine (Phe) isolated from Arctic char samples using CSIA-AAs. We then compared amino acid δ¹⁵ N values from DBSs and the other sample types (whole blood and muscle) from the same specimens. We calculated and compared trophic position estimates generated from whole blood, DBSs, and muscle.

RESULTS

The δ¹⁵ N values of Glu and Phe, as well as trophic position estimates from DBSs, were highly correlated with δ¹⁵ N values and estimates from both whole blood and muscle. The DBS amino acid δ¹⁵ N values and trophic position estimates agreed well with those from whole blood. Although mean differences between amino acid δ¹⁵ N values from DBSs and muscle were noted, the offsets were small and resulted in a 0.2 mean difference between trophic position estimates for DBSs and muscle.

CONCLUSIONS

We demonstrate that the application of CSIA-AAs to field-prepared DBSs of Arctic char generates similar trophic position estimates to those from whole blood and muscle. We suggest that DBSs could be developed as a minimally invasive sampling technique to study feeding ecology of wild fish and perhaps other organisms of interest.