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EBF: reflection on bioanalytical assay requirements used to support liquid microsampling

2014; Future Science Ltd; Volume: 6; Issue: 19 Linguagem: Inglês

10.4155/bio.14.211

1757-6199

Stephen White, Glen Hawthorne, Lieve Dillen, Neil Spooner, Karen Woods, Timothy Sangster, Zoe Cobb, Philip Timmerman,

Single-cell and spatial transcriptomics

BioanalysisVol. 6, No. 19 General Content - EditorialFree AccessEBF: reflection on bioanalytical assay requirements used to support liquid microsamplingStephen White, Glen Hawthorne, Lieve Dillen, Neil Spooner, Karen Woods, Timothy Sangster, Zoe Cobb & Philip TimmermanStephen WhiteBioanalytical Science & Toxicokinetics, Drug Metabolism & Pharmacokinetics, GlaxoSmithKline Research & Development, Ware, UK, Glen HawthorneLGC, UK, Lieve DillenJanssen Research & Development, Belgium, Neil SpoonerBioanalytical Science & Toxicokinetics, Drug Metabolism & Pharmacokinetics, GlaxoSmithKline Research & Development, Ware, UK, Karen WoodsAstra Zeneca, UK, Timothy SangsterCharles River laboratories UK, Zoe CobbLGC, UK & Philip TimmermanJanssen Research & Development, BelgiumPublished Online:20 Nov 2014https://doi.org/10.4155/bio.14.211AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareShare onFacebookTwitterLinkedInRedditEmail Keywords: capillaryEuropean Bioanalysis Forumliquid microsamplingsample homogeneityvalidationFurther to the discussions on the bioanalysis of samples generated using microsampling techniques [1–6] and more specifically the ongoing work of the European Bioanalysis Forum (EBF) Liquid Microsampling Consortium [7], this article seeks to highlight some of the 'philosophical' aspects around liquid microsampling and to introduce some of the experimental elements that will form part of future efforts by the Consortium. Discussion will be focused on three major areas: sample manipulation, homogeneity of samples and validation of assays. The scope of this manuscript will be liquid microsampling and will not focus on adsorption techniques such as dried blood spots (DBS) and solid phase microextraction.Different microsampling techniques have created great interest from toxicokinetic (TK) and pharmacokinetic (PK) scientists, since they offer the potential to reduce sample volumes for exposure assessment in biofluids. For preclinical studies microsampling can facilitate the generation of serial profiles in rodent exposure evaluation studies, rather than working with composite designs. Microsampling has facilitated the removal of satellite animal groups leading to substantial reductions in the number of animals required and the reduction or elimination of rodent warming. Benefits in the clinical environment include the ability to take reduced sample volumes from pediatric, elderly and critically ill patient populations.In a recent publication the NC3R group proposes the following definition of a blood microsample: the sample should ideally not contain more than 50 µl whole blood [8]. As a consequence the subsequent plasma volumes are 20 µl or lower. Another, more philosophical consideration would be the impact of sampling volume on the animal or subject; for example, 50 µl of blood may not be considered as a 'microsample' in the context of juvenile animals or newborn babies. Two major liquid microsampling approaches can be envisaged:• Liquid microsampling (non-capillary) of:– Blood: a low volume of blood is sampled into a small receptacle containing anticoagulant, often diluted before storage;– Plasma: a low volume of blood is sampled into a small receptacle containing anticoagulant, then centrifuged to obtain plasma. Plasma is transferred to a small receptacle or capillary for storage. Dilution strategies can also be considered;– Serum: a low volume of blood is sampled in a small receptacle without anticoagulant, then centrifuged to obtain serum. Serum is transferred to a small receptacle or capillary for storage. Dilution strategies can also be considered.• Capillary microsampling of:– Blood: blood is sampled in a capillary containing anticoagulant, with or without subsequent washout using a diluent at the time of sample collection;– Plasma: blood is sampled in a capillary coated with anticoagulant, then centrifuged to obtain plasma. Subsequently a low volume aliquot of the plasma is transferred into a second capillary (typically 8 or 4 µl). Washout/dilution can be performed immediately or at the start of analysis. Alternatively, the entire plasma volume can be transferred to a small tube and frozen.While serum sampling using capillaries has been previously reported [9], it may be difficult to envisage for routine use, owing to the likelihood of blood clotting during collection of blood in an uncoated capillary.While the greatest reductions in sample volume will be more readily realized by using blood microsampling, as less sample manipulation is required, PK/TK scientists in the drug development space have traditionally relied on (free or total) plasma exposure data for PK, TK and even pharmacodynamic (PD) evaluation [10]. Therefore many are not confident or comfortable with blood exposure data. Interpretation of blood exposure data has been considered more complex, plus blood cell partitioning and hematocrit can influence the results and relation to the free concentration in plasma is less obvious. Nevertheless, revival of blood as a matrix for exposure evaluation would certainly simplify practicalities and logistics from a sample collection perspective.In addition to the blood versus plasma debate, the topic of sampling site is an important aspect for engagement with our stakeholders, but will not be the focus of this discussion.It is worth recognizing that microsampling approaches and technologies are continually being refined and improved. Therefore, as bioanalysts, we should remain alert and flexible and be able to adapt our thinking as new tools and processes are introduced [11]. Recently, the use of blood as the matrix of choice following some adsorption microsampling techniques (such as DBS) has become less favorable for routine regulated bioanalysis owing to concerns around the effect of variable hematocrit or long-term storage when a sub-punch approach is employed [12]. However, it is worth noting that as new technologies are introduced and existing ones are improved, it is quite likely that the interest in using blood and dried blood as the microsampling matrix of choice may once again be seriously considered for regulated bioanalysis.Sample manipulationHow would a bioanalytical lab deal with a microsample?When bioanalytical scientists quantify analytes in plasma, blood is withdrawn from animals or patients and subsequently centrifuged to obtain a plasma fraction, which is then technically a derived sample. This peculiar situation is not present when other biofluids (e.g., urine or cerebrospinal fluid) are sampled; in those cases the primary collected samples are analyzed for PK/TK or PD. In practice, plasma is generally considered as a primary sample, even if some additives are used, for example, to stabilize an analyte of interest. The sample that is generated at or immediately after the moment of collection and that is subsequently stored can be defined as the primary sample. This sample is then used for analysis and is typically also used as the starting material for repeat analysis if required. Also, when introducing additives to urine or cerebrospinal fluid at the time of collection (e.g. to prevent adsorption), this derived sample is stored and used at the time of analysis.Discussion on best practices for liquid microsampling with respect to sample workup has introduced semantics around primary versus secondary samples. These considerations are mainly inspired by the process most commonly applied for (capillary) microsampling, where a wash-out of the blood/plasma using a diluent (typically in excess of the sampled volume in a capillary microsample) is performed. However, it can be argued that these steps are no different from the manipulations and additions commonly introduced for traditional volume (or 'macro') samples.Nevertheless, there are several valid considerations with respect to this sample manipulation step:• The time of the dilution (i.e., immediately after sample collection or at the time of analysis);• Validity of this diluted sample for repeat analysis;• Impact on stability, storage and integrity of the sample.When blood is the bioanalytical matrix of choice, many laboratories dilute with water before freezing in order to lyse red blood cells and to facilitate better sample handling by reducing viscosity. This practice is already widely applied for traditional volume blood samples. Sub-aliquotting whole-blood microsamples without dilution after freezing will be challenging and requires further investigation.Some discomfort exists with the low-volume aliquots being considered (10 µl or less), with the accuracy and precision of the quantitation at these volumes often being questioned. The use of suitable pipettes (positive displacement) and container systems should minimize or eliminate issues associated with these small volumes. Applying the usual assay acceptance criteria may be more challenging, which in turn may force a re-evaluation of what we consider a viable sample volume for regulated bioanalysis. It may be worth reflecting on how this relates to what other analytical areas consider a minimum workable volume and how low can we go while still generating reliable results? Many arguments are driven by the increased focus on validity of sample data, which has resulted in increased regulation with respect to bioanalytical method validation over recent years.Dilution of samples is often performed to safeguard against the potential for repeat analysis. This intervention need not compromise limits of quantification for the bioanalytical assay, since new instruments often offer the enhanced sensitivity required. Furthermore, this approach is likely to minimize any issues associated with the handling of small volumes, assuming that the dilution step is performed accurately. Repeat analysis could also be considered from subsequent aliquots taken from plasma obtained from the same blood collection or from two consecutive and distinct capillary microsamples collected at the same timepoint. Can these samples be considered as truly identical? The answer to this question may be different from a (bio)analytical perspective (ISR) to a pharmacokinetic/pharmacodynamic perspective.The EBF Liquid Microsampling consortium would encourage the following thinking:It is not crucial whether diluent is added at the sample collection site or at the bioanalytical lab, as long as experimental evidence validates the approach. From a practical point of view, addition of diluent may be more favorable at the start of analysis. Intuitively (from a bioanalyst's perspective), adding diluent in the well controlled environment of a bioanalytical lab seems the preferred option, as equipment (i.e., calibrated pipettes) and documented procedures are already in place. Also, plasma sampling in microcapillaries will likely be more labor intensive than traditional sampling, so the introduction of an additional dilution step at the site of sample collection may not be well received. We would recommend against introducing new semantics, such as primary and secondary sample, since definition will be complex and lead to confusion due to different aspects with the many possible approaches that need to be considered.Sample homogeneityIs a blood/plasma microsample at higher risk for non-homogeneity compared with a traditional sample?A key consideration when analyzing biological samples is the homogeneity of the analyte within the sample. Is the analyte able to distribute freely and equally throughout the entire bioanalytical sample? This was perceived as a significant concern when dried blood spots were introduced as an analytical matrix and was subject to much experimental evaluation [13]. The same considerations and thoughts tend to arise for very small liquid volumes, but are these concerns justified?When small sample volumes (<20 µl) are presented for analysis, safeguarding the homogeneity of a subsample is not obvious. Vortexing a microsample in a sample vessel (even in adapted miniaturiazed tubes) to render it homogenous will likely also coat the walls of the sample tube. Sample loss and the potential for adsorption of analytes to container surfaces are serious drawbacks. Conversely, is a traditional sample volume of a biological fluid more ably made homogenous by thorough vortex mixing or inversion of sample vessels? Is it possible to physically observe 'good' mixing? High assay variability or non-linear calibration curves through surface adsorption effects could be indicative of poor homogeneity.One way to overcome this perceived issue could be addition of a diluent to the entire small volume, in order to enable thorough mixing and if the diluent is selected judiciously, could reduce adsorption effects. However, this would need to be performed with known accurate volumes of sample and diluents. Another approach may be to prepare quality controls in the same volume as the (undiluted) study samples with testing of multiple aliquots to assess reproducibility. Mixing by repeated aspirating and dispensing before sampling should also be considered. In any event, whichever microsampling approach is adopted (i.e., with or without a dilution step), it is certainly feasible to improve, or assess analyte homogeneity within the sample. At present, the perception of poor homogeneity with small sample volumes is a concern that is not yet supported by data. As we continue to investigate further through targeted experiments, we will as a community gain better insight on this topic.When small sample volumes are stored in the freezer for longer time periods, the volume/surface ratios are potentially less favorable depending on the containers used, compared with traditional sample volumes. As a consequence freeze-drying (or evaporation) effects could be observed following prolonged storage in the freezer. Questions remain under which conditions (volume, temperature, duration, container) can we expect these effects to play a role. Preparation and storage of quality controls in comparable volumes (whether diluted or undiluted) and storage containers will certainly give confidence that any effects are adequately under control.To assure accurate volumes when working with very small samples it could be advisable to encase the sample within a capillary. Reduced exposure to the atmosphere and collection of the sample within the smallest vessel available can be realized. However, given the restrictive dimensions of a glass capillary it is not viable to vortex mix the samples to evenly distribute the analyte within the capillary. So when a plasma sample has been 'fixed' in a capillary, is the analyte homogenous along the full length of that capillary? This can be assessed by taking subsamples into fresh capillaries of smaller volume and checking the subsamples for comparability along the length of the collection capillary. In addition, experiments to explore and compare the effect of different container systems can be incorporated into assay development and validation.Until this point we have only considered the homogeneity of the analyte, either within a small volume sample in a vial or within a small volume sample in a capillary. What about the biological matrix? Does this remain the same for a microsample compared with a traditional sample? While the 'simple' separation of blood cellular components to form plasma is conducted through centrifugation, is the plasma generated from blood within a capillary identical to plasma generated from blood collected into a tube? Is an equivalent centrifugal force applied to separate blood cells and plasma within a capillary and more importantly does it impact the quantitative assay? This can be investigated by spiking analyte into blood and harvesting plasma from a capillary versus a traditional sample tube.Anticoagulants are usually added to blood samples to prevent clotting – are these present in the same concentrations in a capillary microsample compared with a non-capillary blood sample? When using capillaries coated with anticoagulant, does the blood 'extract' the anticoagulant from the capillary surface as it transits along the capillary, thus creating a concentration gradient of anticoagulant along the length of the capillary. If so, will the concentration of the anticoagulant at the sampling end of the capillary still be sufficient to prevent clotting? More importantly, does this have any impact upon the quantitative data derived?While these questions are important to understand, this should be put in perspective. For traditional sample volumes, less sample volume is sometimes collected than anticipated – meaning that the concentration of anticoagulant may vary between different sample collections in the same TK/PK profile.The simple and pragmatic solutions to the questions raised in this section can be proven by adequate method validation, demonstrating the ability to collect in vivo blood samples, derive plasma samples and analyze them with adequate robustness and confidence to give high-quality quantitative data.Assay validation considerationsWhat (if any) changes are required compared with a 'traditional' assay validation?When using an existing assay validated for traditional matrix volumes to support the bioanalysis of a study using microsampling, or indeed when validating a new assay for this purpose, consideration should be given to the suitability of the assay validation, both in terms of the sample origin and the endpoint for which the data are intended. It may be, depending on the nature of the microsamples collected, that additional validation experiments should be considered. Conversely, it is possible that the nature of the microsampling technique could actually eliminate the need for certain validation experiments or require modification of these experiments.EBF member companies were asked to describe any additional investigations that they would include in method development, or assay validation for support of liquid microsampling. Members were also asked which (if any) routine validation experiments were considered not (or less) relevant for the bioanalysis of microsamples. Of the 21 companies to respond, 11 gave insight into their current experience in validating assays for microsamples, with respect to both small molecules (by LC–MS/MS) and macromolecules (by ligand binding assay [LBA]):With respect to modified/adapted validation experiments the responses included:• Matrix stability of small sample volumes;• Stability in glass capillaries;• Matrix stability of diluted samples;• Whole-blood stability in a capillary prior to plasma harvest.The intrinsic stability of an analyte should not change because of sample volume or container. However if evaporation occurs due to low volume, versus high surface area in a container, the apparent stability may be affected. With microcapillary sampling, when the sample is stored in the capillary (both for blood or plasma) before dilution/washout, then this storage period should be covered by the correct stability evaluations. When microsamples are diluted at the time of sampling or analysis followed by further storage, then the stability of the analyte in the diluted sample will be part of the stability program. Finally it should be mentioned that, irrespective of sample volume, the practical challenges and relevance of performing blood stability experiments has additional limited value over plasma stability. Unless for known chemical classes, plasma stability has been proven to be a good surrogate for blood stability [14].• Adsorption at container surfaces and impact on recovery: it is desirable that the analyte should be fully recovered from the capillary upon washout. Dependent on the choice of the washout solvent/diluents, the recovery can be controlled and should be proven during method development or validation;• Sample homogeneity: as discussed previously, sample homogeneity seems to be a concern for many bioanalysts. Comparison of quantitative results obtained for traditional and microsamples can reveal whether concerns are justified. Other approaches may include testing of multiple aliquots from a single 'micro quality control' to monitor homogeneity.It is fair to say that the nature and design of these additional or adapted validation experiments will vary depending upon the microsampling technique used. However in general, the inclusion of validation samples prepared, processed and stored in the same manner as unknown study samples, will typically alleviate many of the potential concerns.With regard to validation experiments considered less relevant or appropriate, generally most respondents felt that all routine validation experiments should be included. One exception was the generation of freeze–thaw stability; depending upon the nature of the microsamples, respondents would consider removing this experiment or limit to a single freeze–thaw cycle of the (capillary) microsample. Again, the elements covered during an assay validation should be relevant to the samples analyzed. Thus, if study microsamples cannot possibly undergo more than one freeze–thaw cycle, the relevance of investigating more cycles could legitimately be questioned.One topic highlighted as a potential area of concern was the stabilization of unstable drugs or metabolites. Where microsamples are collected using capillaries, the means to stabilize labile drugs and/or metabolites is not immediately obvious. For traditional volume samples, blood can be collected directly into devices that contain stabilizing additives and by inference the resulting plasma is stabilized. Capillaries coated with EDTA are commercially available, while capillaries coated with other coagulants or inclusion of stabilizing agents are not widely available. One could envisage this changing as demand for other capillary coatings increases, but for now microsampling for unstable analytes may be a limitation or require alternate processes during sample collection.ConclusionGoing forward, it is anticipated that many of the above elements will be discussed and investigated further by the Consortium as it begins to design an experimental work plan. Once prepared, the experimental plan will be executed by each Consortium member company on a variety of analytes covering as diverse a chemical space as possible. It is also envisaged that both chromatographic and ligand-binding assay endpoints will be incorporated, depending on the analytes being tested. The main areas of focus for the upcoming experimental work will likely be:• Various stability considerations unique to microsamples;• Container factors and manipulation of small volumes;• Analyte and matrix homogeneity.It is foreseen that some of the experimental considerations or 'worries' will be dispelled as just that, while others may require the inclusion of targeted experiments during the method development and assay validation. A better understanding of how to deal with microsamples in the bioanalytical laboratory and to ensure adequate assay robustness for analyzing these samples will ultimately facilitate widespread uptake of microsampling and help realize the important benefits of reducing sample volumes.DisclaimerThe views and conclusion presented in this paper are those of the EBF and do not necessarily reflect the representative affiliation or company's position on the subject.Financial & competing interests disclosureThe authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.No writing assistance was utilized in the production of this manuscript.References1 Nilsson L, Ahnoff M, Jonsson O. Capillary microsampling in the regulatory environment: validation and use of bioanalytical capillary microsampling methods. Bioanalysis 5(6), 731–738 (2013).Link, CAS, Google Scholar2 Spreadborough M, Day J, Jackson-Addie K et al. Bioanalytical implementation of plasma capillary microsampling: small hurdles, large gains. Bioanalysis 5(12), 1485–1489 (2013).Link, CAS, Google Scholar3 Microsampling in Pharmaceutical Bioanalysis. Zane P, Emmons G (Eds). Future Science Ltd, London, UK (2013). Crossref, Google Scholar4 Timmerman P, White S, Cobb Z et al. Update of the EBF recommendation for the use of DBS in regulated bioanalysis integrating the conclusions from the EBF DBS-microsampling consortium. Bioanalysis 5(17), 2129–2136 (2013).Link, CAS, Google Scholar5 Dillen L, Loomans T, Van de Perre G et al. Blood microsampling using capillaries for drug-exposure determination in early preclinical studies: a beneficial strategy to reduce blood sample volumes. Bioanalysis 6(3), 293–306 (2014).Link, CAS, Google Scholar6 Liederer BM, Berezhkovskiy LM, Ubhayakar SS et al. An alternative approach for quantitative bioanalysis using diluted blood to profile oral exposure of small molecule anticancer drugs in mice. J. Pharm. Sci. 102(2), 750–760 (2013).Crossref, Medline, CAS, Google Scholar7 Timmerman P, White S, Cobb Z et al. European Bioanalysis Forum continued plans to support liquid microsampling. Bioanalysis 6(14) 1897–1900 (2014).Link, CAS, Google Scholar8 Chapman K, Chivers S, Gliddon D et al. Overcoming the barriers to the uptake of nonclinical microsampling in regulatory safety studies. Drug Discov. Today 19(5), 528–532 (2014).Crossref, Medline, CAS, Google Scholar9 Jonsson O, Steffen AC, Sundquist VS et al. Capillary microsampling and analysis of 4-µl blood, plasma and serum samples to determine human α-synuclein elimination rate in mice. Bioanalysis 5(4), 449–462 (2013).Link, CAS, Google Scholar10 Emmons G, Rowland M. Pharmacokinetic considerations as to when to use dried blood spot sampling. Bioanalysis 2(11), 1791–1796 (2010).Link, CAS, Google Scholar11 Bowen C, Licea-Perez H, Karlinsey M et al. A novel approach to capillary plasma microsampling for quantitative bioanalysis. Bioanalysis 5(9), 1131–1135 (2013).Link, CAS, Google Scholar12 De Vries R, Barfield M, van de Merbel N et al. The effect of hematocrit on bioanalysis of DBS: results from the EBF DBS-microsampling consortium. Bioanalysis 5(17), 2147–2160 (2013).Link, CAS, Google Scholar13 Cobb Z, de Vries R, Spooner N et al. In-depth study of homogeneity in DBS using two different techniques: results from the EBF DBS-microsampling consortium. Bioanalysis 5(17), 2161–2169 (2013).Link, CAS, Google Scholar14 Freisleben A, Brudny-Klöppel M, Mulder H et al. Blood stability testing: European Bioanalysis Forum view on current challenges for regulated bioanalysis. 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This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.No writing assistance was utilized in the production of this manuscript.PDF download