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Background Virus neutralising antibodies in serum are considered key correlates of protection for vaccines and monoclonal antibodies against respiratory syncytial virus (RSV). RSM01 is a novel, highly-potent, half-life-extended and fully-human monoclonal antibody candidate targeting the RSV prefusion F protein. Currently in Phase 1 development, RSM01 is primarily being developed to potentially provide an effective and affordable RSV prevention strategy in low- and middle-income countries. To evaluate the ability of dried blood collection to generate data sets and conclusions comparable to serum collection, we compared pharmacokinetics (PK) of RSM01, immunogenicity, and virus neutralisation for dried capillary blood samples with serum samples. Methods RSM01 PK, anti-drug antibodies (ADA), and RSV-neutralising antibodies from the Phase 1 trial were analyzed and compared between matched serum and dried blood samples. Deming regression analysis was performed using baseline-corrected values to evaluate correlation between measurements in liquid serum versus dried blood. Results The analysis showed good correlation (R 2  > 0.95) between individual RSM01 concentrations measured in both serum and capillary blood. Analysis of RSM01 PK parameters in capillary blood yielded equivalent conclusions as from serum. A strong correlation (R 2  > 0.95) was observed between RSV neutralising activity measured in both serum and capillary blood. In addition, RSV neutralising activity was correlated with RSM01 concentrations in both serum and capillary blood data sets. For ADA, individual sample results had 96% agreement (290/302) and overall participant ADA status had 93% agreement (52/56). Conclusions Both RSM01 concentrations and RSV neutralising activity showed a strong correlation between the serum and blood measurements. ADA measurements also had an agreement of > 90% for individual samples and overall participant status. Our results demonstrate that dried blood is a suitable specimen type for collection and evaluation in the RSM01 clinical development program and shows promise as a useful approach to reduce patient burden in clinical trials, particularly for infants in low- and middle-income countries. Trial Registration Clinicaltrials.gov NCT05118386 November 12, 2021.

Background and Objective Phenotyping cocktails use a combination of cytochrome P450 (CYP)-specific probe drugs to simultaneously assess the activity of different CYP isoforms. To improve the clinical applicability of CYP phenotyping, the main objectives of this study were to develop a new cocktail based on probe drugs that are widely used in clinical practice and to test whether alternative sampling methods such as collection of dried blood spots (DBS) or saliva could be used to simplify the sampling process. Methods In a randomized crossover study, a new combination of commercially available probe drugs (the Basel cocktail) was tested for simultaneous phenotyping of CYP1A2, CYP2B6, CYP2C9, CYP2C19, CYP2D6 and CYP3A4. Sixteen subjects received low doses of caffeine, efavirenz, losartan, omeprazole, metoprolol and midazolam in different combinations. All subjects were genotyped, and full pharmacokinetic profiles of the probe drugs and their main metabolites were determined in plasma, dried blood spots and saliva samples. Results The Basel cocktail was well tolerated, and bioequivalence tests showed no evidence of mutual interactions between the probe drugs. In plasma, single timepoint metabolic ratios at 2 h (for CYP2C19 and CYP3A4) or at 8 h (for the other isoforms) after dosing showed high correlations with corresponding area under the concentration–time curve (AUC) ratios (AUC 0–24h parent /AUC 0–24h metabolite ) and are proposed as simple phenotyping metrics. Metabolic ratios in dried blood spots (for CYP1A2 and CYP2C19) or in saliva samples (for CYP1A2) were comparable to plasma ratios and offer the option of minimally invasive or non-invasive phenotyping of these isoforms. Conclusions This new combination of phenotyping probe drugs can be used without mutual interactions. The proposed sampling timepoints have the potential to facilitate clinical application of phenotyping but require further validation in conditions of altered CYP activity. The use of DBS or saliva samples seems feasible for phenotyping of the selected CYP isoforms.

Introduction: A lack of access to hepatitis C virus (HCV) diagnostics is a significant barrier to achieving the World Health Organization 2030 global elimination goal. HCV core antigen (HCVcAg) quantification and dried blood spot (DBS) are appealing alternatives to conventional HCV serology and nucleic acid testing (NAT) for resource‐constraint settings, particularly in difficult‐to‐reach populations. We assessed the accuracy of serum and DBS HCVcAg testing in people who inject drugs in Tanzania using HCV NAT as a reference. Method: Between May and July 2015, consecutive HCV‐seropositive patients enrolled in the local opioid substitution treatment centre were invited to participate in the study. All had HCV RNA detection (Roche Molecular Systems, Pleasanton, CA, USA), genotyping (NS5B gene phylogenetic analysis) and HCVcAg on blood samples and DBS (Architect assay; Abbott Diagnostics, Chicago, IL, USA). Results: Out of 153 HCV‐seropositive individuals, 65 (42.5%) and 15 (9.8%) were co‐infected with HIV (41 (63%) were on anti‐retroviral therapy (ARVs)) and hepatitis B respectively. In total, 116 were viraemic, median viral load of 5.7 (Interquartile range (IQR); 4.0–6.3) log iU/ml (75 (68.2%) were genotype 1a, 35 (31.8%) genotype 4a). The median alanine transaminase (ALT) (iU/l), aspartate transaminase (AST) (iU/l) and gamma‐glutamyl transferase (GGT) (iU/l) were 35 (IQR; 23–51), 46 (32–57) and 69 (35–151) respectively. For the quantification of HCV RNA, serum HCVcAg had a sensitivity at 99.1% and a specificity at 94.1%, with an area under the receiver operating curve (AUROC) at 0.99 (95% CI 0.98–1.00). DBS HCVcAg had a sensitivity of 76.1% and a specificity of 97.3%, with an AUROC of 0.87 (95% CI 0.83–0.92). HCVcAg performance did not differ by HIV co‐infection or HCV genotype. Conclusions: Our study suggests that HCVcAg testing in serum is an excellent alternative to HCV polymerase chain reaction in Africa. Although HCVcAg detection and quantification in DBS has a reduced sensitivity, its specificity and accuracy are good and it could therefore be used for scaling up HCV testing and care in resource‐limited African settings.

Dried blood spot (DBS) samples can be used for the detection of severe acute respiratory syndrome coronavirus 2 spike antibodies. DBS sampling is comparable to matched serum samples with a relative 98.1% sensitivity and 100% specificity. Thus, DBS sampling offers an alternative for population-wide serologic testing in the coronavirus pandemic.

This article discusses dried blood spot (DBS) sampling in therapeutic drug monitoring (TDM). The most important advantages of DBS sampling in TDM are the minimally invasive procedure of a finger prick (home sampling), the small volume (children), and the stability of the analyte. Many assays in DBS have been reported in the literature over the previous 5 years. These assays and their analytical techniques are reviewed here. Factors that may influence the accuracy and reproducibility of DBS methods are also discussed. Important issues are the correlation with plasma/serum concentrations and the influence of hematocrit on spot size and recovery. The different substrate materials are considered. DBS sampling can be a valid alternative to conventional venous sampling. However, patient correlation studies are indispensable to prove this. Promising developments are dried plasma spots using membrane and hematocrit correction using the potassium concentration.

The added value of dried blood spot (DBS) samples complementing the information obtained from commonly routine doping control matrices is continuously increasing in sports drug testing. In this project, a robotic-assisted non-destructive hematocrit measurement from dried blood spots by near-infrared spectroscopy followed by a fully automated sample preparation including strong cation exchange solid-phase extraction and evaporation enabled the detection of 46 lower molecular mass (< 2 kDa) peptide and non-peptide drugs and drug candidates by means of LC-HRMS. The target analytes included, amongst others, agonists of the gonadotropin-releasing hormone receptor, the ghrelin receptor, the human growth hormone receptor, and the antidiuretic hormone receptor. Furthermore, several glycine derivatives of growth hormone–releasing peptides (GHRPs), arguably designed to undermine current anti-doping testing approaches, were implemented to the presented detection method. The initial testing assay was validated according to the World Anti-Doping Agency guidelines with estimated LODs between 0.5 and 20 ng/mL. As a proof of concept, authentic post-administration specimens containing GHRP-2 and GHRP-6 were successfully analyzed. Furthermore, DBS obtained from a sampling device operating with microneedles for blood collection from the upper arm were analyzed and the matrix was cross-validated for selected parameters. The introduction of the hematocrit measurement method can be of great value for doping analysis as it allows for quantitative DBS applications by managing the well-recognized “hematocrit effect.”

The Alzheimer's Association's multi-tiered approach to Alzheimer's disease (AD) staging (Jack, C., et al. 2024) via Core 1 and Core 2 biomarkers reflects the interplay between amyloid, tau, neurodegeneration, inflammation, and co-occurring pathologies and subsequent effects on symptom manifestation and progression. A single biomarker will probably not be sufficient for characterizing these complexities. The NULISAseq CNS disease panel allows simultaneous detection of 100+ biomarkers related to central nervous system (CNS) dysfunction across a broad dynamic range. Low sample volume requirements (25uL) are amenable to capillary blood analyses via remote collection devices, a scalable approach for obtaining CNS protein profiles from those that are unable to undergo traditional biomarker evaluation. A stepwise approach was used to explore the effects of buffer composition, volume, and incubation time on the percent recovery (%R) of target analytes collected via Telimmune plasma separator cards relative to analyte concentrations in paired plasma. After selecting the optimum conditions, paired venous plasma samples and capillary dried plasma spots (DPS) from N = 40 Wisconsin Registry for Alzheimer's Prevention and the Wisconsin Alzheimer's Disease Center participants (N = 36 cognitively unimpaired, N = 4 impaired) were analyzed using the NULISAseq CNS disease panel. Analyte recovery, detectability, and Spearman correlations were compared across sample types. The highest DPS detectability (80%) was achieved using 80uL of Alamar sample diluent spiked with a cocktail of peptidases and phosphatases. Decreasing buffer volume resulted in increasing detectability (R =1.00) down to at least 80uL. Incubation time did not have an obvious effect on detectability. In participant DPS samples, %R(SD) relative to plasma ranged from 77(4)% to 92(5)% for pTau species. Sixty-two of 127 analytes were significantly correlated in DPS and plasma. Here, we report optimization and evaluation of capillary DPS samples with a targeted proteomic panel. Analyte recovery and correlations in DPS compared to plasma varied widely depending on the analyte. This is to be expected given the diversity of targets across the panel. Ongoing work includes evaluation in an amyloid-enriched cohort, additional optimization for detecting AD-related markers, and head-to-head evaluation of other remote sampling devices.

Several external and internal factors can affect the performance and variability of Hemoglobin concentration [Hb] measurements using HemoCue, and documentation on the contribution of different sources of [Hb] variation is limited. We used an experimental repeated measurements design with nine randomly selected participants, three HemoCue devices, and three trained field workers. HemoCue measurements for all samples were repeated three times. The [Hb] measurement system considers four sources of error: 1) HemoCue devices, 2) field workers, 3) between individuals, and 4) within individuals. A concordance analysis was used to assess accuracy and precision, and a linear mixed model was used to estimate mean differences (bias) from blood specimens, anticoagulants, and to estimate the contribution of the 4 sources of error to [Hb] measurements. Positive mean [Hb] differences were found: 1.34 g/dL for capillary drops, 0.81 g/dL for pooled capillary blood samples, 0.756 g/dL for venous blood stored with EDTA, and 0.911 g/dL for venous blood stored with heparin. The mean [Hb] difference for venous blood with EDTA was used as a correction factor for all results measured using a HemoCue. After adjustment, capillary drops showed a mean difference of 0.585 g/dL, and pooled capillary samples were not significantly different. The individual variability was 95.8% of total variance, HemoCue devices contributed 2.1% of measurement error, field staff contributed 0.4%, and the residual was 1.7%. The HemoCue [Hb] measurement system is reliable in controlled environments, with a small measurement error of 4.2%.

The follow-up of patients under lifelong immunosuppressant therapy is pivotal to prevent allograft rejection after transplant. Part of the difficulties associated with routine monitoring of immunosuppressant concentrations can be alleviated by home sampling using dried blood spots (DBSs). To evaluate the applicability of a DBS method for the determination of immunosuppressants in venous blood samples, making use of an automated extraction platform. Paired venous DBSs and whole blood samples were analyzed for tacrolimus (n = 162), sirolimus (n = 47), everolimus (n = 45), and cyclosporin A (n = 61) with liquid chromatography coupled to tandem mass spectrometry, using fully automated extraction for DBSs. Agreement between the automated DBS and whole blood method was assessed by using Bland-Altman comparison. Both an analytical and a clinical acceptance limit were predefined at more than 67% of all paired samples within 20% of the mean of both samples and more than 80% of all paired samples within 20% of the whole blood concentration, respectively. An impact of the hematocrit (hct) on DBS quantitation was observed for all analytes, which could be alleviated for all analytes by using a hct conversion formula based on a tacrolimus data subset: [DBScorrected] = [DBSmeasured]/(1.6305 - 1.559*hct). After correction, both analytical and clinical acceptance criteria were met for all analytes. Automated DBS analysis shows great potential for routine therapeutic drug monitoring of immunosuppressants, avoiding any manual sample handling.

Establishing nucleic acid-based assays for genetic newborn screening (NBS) provides the possibility to screen for genetically encoded diseases like spinal muscular atrophy (SMA), best before the onset of symptoms. Such assays should be easily scalable to 384-well reactions that make the screening of up to 2000 samples per day possible. We developed a test procedure based on a cleanup protocol for dried blood spots and a quantitative (q)PCR to screen for a homozygous deletion of exon 7 of the survival of motor neuron 1 gene (SMN1) that is responsible for >95% of SMA patients. Performance of this setup is evaluated in detail and tested on routine samples. Our cleanup method for nucleic acids from dried blood spots yields enough DNA for diverse subsequent qPCR applications. To date, we have applied this approach to test 213,279 samples within 18 months. Thirty patients were identified and confirmed, implying an incidence of 1:7109 for the homozygous deletion. Using our cleanup method, a rapid workflow could be established to prepare nucleic acids from dried blood spot cards. Targeting the exon 7 deletion, no invalid, false-positive, or false-negative results were reported to date. This allows timely identification of the disease and grants access to the recently introduced treatment options, in most cases before the onset of symptoms. Carriers are not identified, thus, there are no concerns of whether to report them.